[PATCH 0/2] hwmon: Add Baikal-T1 SoC Process, Voltage and Temp sensor support

[PATCH 0/2] hwmon: Add Baikal-T1 SoC Process, Voltage and Temp sensor support

[Sergey.Semin]

From: Serge Semin <fancer.lancer@gmail.com>

In order to keep track of Baikal-T1 SoC power consumption and make sure
the chip heating is within the normal temperature limits, there is
a dedicated hardware monitor sensor embedded into the SoC. It is based
on the Analog Bits PVT sensor but equipped with a vendor-specific control
wrapper, which ease an access to the sensors functionality. Fist of all it
provides an accessed to the sampled Temperature, Voltage and
Low/Standard/High Voltage thresholds. In addition the wrapper generates
an interrupt in case if one enabled for alarm thresholds or data ready
event. All of these functionality is implemented in the Baikal-T1 PVT
driver submitted within this patchset. Naturally there is also a patch,
which creates a corresponding yaml-based dt-binding file for the sensor.

This patchset is rebased and tested on the mainline Linux kernel 5.6-rc4:
commit 98d54f81e36b ("Linux 5.6-rc4").

Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Signed-off-by: Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>
Signed-off-by: Maxim Kaurkin <Maxim.Kaurkin@baikalelectronics.ru>
Cc: Pavel Parkhomenko <Pavel.Parkhomenko@baikalelectronics.ru>
Cc: Ramil Zaripov <Ramil.Zaripov@baikalelectronics.ru>
Cc: Ekaterina Skachko <Ekaterina.Skachko@baikalelectronics.ru>
Cc: Vadim Vlasov <V.Vlasov@baikalelectronics.ru>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Paul Burton <paulburton@kernel.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Jean Delvare <jdelvare@suse.com>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: linux-hwmon@vger.kernel.org
Cc: devicetree@vger.kernel.org
Cc: linux-kernel@vger.kernel.org

Serge Semin (2):
  dt-bindings: hwmon: Add Baikal-T1 PVT sensor bindings
  hwmon: Add Baikal-T1 PVT sensor driver

 .../devicetree/bindings/hwmon/be,bt1-pvt.yaml |  100 ++
 Documentation/hwmon/bt1-pvt.rst               |  113 ++
 drivers/hwmon/Kconfig                         |   29 +
 drivers/hwmon/Makefile                        |    1 +
 drivers/hwmon/bt1-pvt.c                       | 1147 +++++++++++++++++
 drivers/hwmon/bt1-pvt.h                       |  266 ++++
 6 files changed, 1656 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/hwmon/be,bt1-pvt.yaml
 create mode 100644 Documentation/hwmon/bt1-pvt.rst
 create mode 100644 drivers/hwmon/bt1-pvt.c
 create mode 100644 drivers/hwmon/bt1-pvt.h

-- 
2.25.1

[PATCH v2 0/2] hwmon: Add Baikal-T1 SoC Process, Voltage and Temp sensor support

[Serge Semin]

In order to keep track of Baikal-T1 SoC power consumption and make sure
the chip heating is within the normal temperature limits, there is
a dedicated hardware monitor sensor embedded into the SoC. It is based
on the Analog Bits PVT sensor but equipped with a vendor-specific control
wrapper, which ease an access to the sensors functionality. Fist of all it
provides an accessed to the sampled Temperature, Voltage and
Low/Standard/High Voltage thresholds. In addition the wrapper generates
an interrupt in case if one enabled for alarm thresholds or data ready
event. All of these functionality is implemented in the Baikal-T1 PVT
driver submitted within this patchset. Naturally there is also a patch,
which creates a corresponding yaml-based dt-binding file for the sensor.

This patchset is rebased and tested on the mainline Linux kernel 5.6-rc4:
base-commit: 0e698dfa2822 ("Linux 5.7-rc4")
tag: v5.7-rc4

Note new vendor prefix for Baikal-T1 PVT device will be added in the
framework of the next patchset:
https://lkml.org/lkml/2020/5/6/1047

Changelog v2:
- Don't use a multi-arg clock phandle reference in the examples dt-bindings
  property. Thus reundant include pre-processor statement can be removed.
- Rearrange the SoBs with adding Maxim' co-development tag.
- Lowercase the node-name in the dt-schema example.
- Add dual license header to the dt-bindings file.
- Replace "additionalProperties: false" property with
  "unevaluatedProperties: false".
- Discard label definition from the binding example.
- Discard handwritten IO-access wrappers. Use normal readl/writel instead.
- Use generic FIELD_{GET,PREP} macros instead of handwritten ones.
- Since the driver depends on the OF config we can remove of_match_ptr()
  macro utilization.
- Don't print error-message if no platform IRQ found. Just return an error.
- Remove probe-status info string printout.
- Our corporate email server doesn't change Message-Id anymore, so the patchset
  is resubmitted being in the cover-letter-threaded format.

Co-developed-by: Maxim Kaurkin <maxim.kaurkin@baikalelectronics.ru>
Signed-off-by: Maxim Kaurkin <Maxim.Kaurkin@baikalelectronics.ru>
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Cc: Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>
Cc: Pavel Parkhomenko <Pavel.Parkhomenko@baikalelectronics.ru>
Cc: Ramil Zaripov <Ramil.Zaripov@baikalelectronics.ru>
Cc: Ekaterina Skachko <Ekaterina.Skachko@baikalelectronics.ru>
Cc: Vadim Vlasov <V.Vlasov@baikalelectronics.ru>
Cc: Alexey Kolotnikov <Alexey.Kolotnikov@baikalelectronics.ru>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Paul Burton <paulburton@kernel.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: linux-mips@vger.kernel.org
Cc: linux-hwmon@vger.kernel.org
Cc: devicetree@vger.kernel.org
Cc: linux-kernel@vger.kernel.org

Serge Semin (2):
  dt-bindings: hwmon: Add Baikal-T1 PVT sensor binding
  hwmon: Add Baikal-T1 PVT sensor driver

 .../bindings/hwmon/baikal,bt1-pvt.yaml        |   95 ++
 Documentation/hwmon/bt1-pvt.rst               |  113 ++
 drivers/hwmon/Kconfig                         |   29 +
 drivers/hwmon/Makefile                        |    1 +
 drivers/hwmon/bt1-pvt.c                       | 1154 +++++++++++++++++
 drivers/hwmon/bt1-pvt.h                       |  237 ++++
 6 files changed, 1629 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/hwmon/baikal,bt1-pvt.yaml
 create mode 100644 Documentation/hwmon/bt1-pvt.rst
 create mode 100644 drivers/hwmon/bt1-pvt.c
 create mode 100644 drivers/hwmon/bt1-pvt.h

-- 
2.25.1

[PATCH v2 1/2] dt-bindings: hwmon: Add Baikal-T1 PVT sensor binding

[Serge Semin]

Baikal-T1 SoC is equipped with an embedded process, voltage and
temperature sensor to monitor the chip internal environment like
temperature, supply voltage and transistors performance.

This bindings describes the external Baikal-T1 PVT control interfaces
like MMIO registers space, interrupt request number and clocks source.
These are then used by the corresponding hwmon device driver to
implement the sysfs files-based access to the sensors functionality.

Co-developed-by: Maxim Kaurkin <maxim.kaurkin@baikalelectronics.ru>
Signed-off-by: Maxim Kaurkin <maxim.kaurkin@baikalelectronics.ru>
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Cc: Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Paul Burton <paulburton@kernel.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: linux-mips@vger.kernel.org

---

Changelog v2:
- Lowercase the node-name in the example.
- Add dual-license header.
- Don't use a multi-arg clock phandle reference in the examples dt-binding
  property. Thus reundant include pre-processor statement can be removed.
- Replace "additionalProperties: false" property with
  "unevaluatedProperties: false".
- Discard label definition from the example.
- Align settings of the "#thermal-sensor-cells" property with two spaces
  ahead of the property line start.
---
 .../bindings/hwmon/baikal,bt1-pvt.yaml        | 95 +++++++++++++++++++
 1 file changed, 95 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/hwmon/baikal,bt1-pvt.yaml

diff --git a/Documentation/devicetree/bindings/hwmon/baikal,bt1-pvt.yaml b/Documentation/devicetree/bindings/hwmon/baikal,bt1-pvt.yaml
new file mode 100644
index 000000000000..c44500ab3045
--- /dev/null
+++ b/Documentation/devicetree/bindings/hwmon/baikal,bt1-pvt.yaml
@@ -0,0 +1,95 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+# Copyright (C) 2020 BAIKAL ELECTRONICS, JSC
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/hwmon/baikal,bt1-pvt.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Baikal-T1 PVT Sensor
+
+maintainers:
+  - Serge Semin <fancer.lancer@gmail.com>
+
+description: |
+  Baikal-T1 SoC provides an embedded process, voltage and temperature
+  sensor to monitor an internal SoC environment (chip temperature, supply
+  voltage and process monitor) and on time detect critical situations,
+  which may cause the system instability and even damages. The IP-block
+  is based on the Analog Bits PVT sensor, but is equipped with a dedicated
+  control wrapper, which provides a MMIO registers-based access to the
+  sensor core functionality (APB3-bus based) and exposes an additional
+  functions like thresholds/data ready interrupts, its status and masks,
+  measurements timeout. Its internal structure is depicted on the next
+  diagram:
+
+     Analog Bits core                     Bakal-T1 PVT control block
+  +--------------------+                  +------------------------+
+  | Temperature sensor |-+         +------| Sensors control        |
+  |--------------------| |<---En---|      |------------------------|
+  | Voltage sensor     |-|<--Mode--| +--->| Sampled data           |
+  |--------------------| |<--Trim--+ |    |------------------------|
+  | Low-Vt sensor      |-|           | +--| Thresholds comparator  |
+  |--------------------| |---Data----| |  |------------------------|
+  | High-Vt sensor     |-|           | +->| Interrupts status      |
+  |--------------------| |--Valid--+-+ |  |------------------------|
+  | Standard-Vt sensor |-+         +---+--| Interrupts mask        |
+  +--------------------+                  |------------------------|
+           ^                              | Interrupts timeout     |
+           |                              +------------------------+
+           |                                        ^  ^
+  Rclk-----+----------------------------------------+  |
+  APB3-------------------------------------------------+
+
+  This bindings describes the external Baikal-T1 PVT control interfaces
+  like MMIO registers space, interrupt request number and clocks source.
+  These are then used by the corresponding hwmon device driver to
+  implement the sysfs files-based access to the sensors functionality.
+
+properties:
+  compatible:
+    const: baikal,bt1-pvt
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+  clocks:
+    items:
+      - description: PVT reference clock
+      - description: APB3 interface clock
+
+  clock-names:
+    items:
+      - const: ref
+      - const: pclk
+
+  "#thermal-sensor-cells":
+    description: Baikal-T1 can be referenced as the CPU thermal-sensor
+    const: 0
+
+unevaluatedProperties: false
+
+required:
+  - compatible
+  - reg
+  - interrupts
+  - clocks
+  - clock-names
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/mips-gic.h>
+
+    pvt@1f200000 {
+      compatible = "baikal,bt1-pvt";
+      reg = <0x1f200000 0x1000>;
+      #thermal-sensor-cells = <0>;
+
+      interrupts = <GIC_SHARED 31 IRQ_TYPE_LEVEL_HIGH>;
+
+      clocks = <&ccu_sys>, <&ccu_sys>;
+      clock-names = "ref", "pclk";
+    };
+...
-- 
2.25.1

Re: [PATCH v2 1/2] dt-bindings: hwmon: Add Baikal-T1 PVT sensor binding

[Rob Herring]

On Sun, 10 May 2020 13:32:10 +0300, Serge Semin wrote:
> Baikal-T1 SoC is equipped with an embedded process, voltage and
> temperature sensor to monitor the chip internal environment like
> temperature, supply voltage and transistors performance.
> 
> This bindings describes the external Baikal-T1 PVT control interfaces
> like MMIO registers space, interrupt request number and clocks source.
> These are then used by the corresponding hwmon device driver to
> implement the sysfs files-based access to the sensors functionality.
> 
> Co-developed-by: Maxim Kaurkin <maxim.kaurkin@baikalelectronics.ru>
> Signed-off-by: Maxim Kaurkin <maxim.kaurkin@baikalelectronics.ru>
> Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
> Cc: Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>
> Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
> Cc: Paul Burton <paulburton@kernel.org>
> Cc: Ralf Baechle <ralf@linux-mips.org>
> Cc: Arnd Bergmann <arnd@arndb.de>
> Cc: Jonathan Corbet <corbet@lwn.net>
> Cc: linux-mips@vger.kernel.org
> 
> ---
> 
> Changelog v2:
> - Lowercase the node-name in the example.
> - Add dual-license header.
> - Don't use a multi-arg clock phandle reference in the examples dt-binding
>   property. Thus reundant include pre-processor statement can be removed.
> - Replace "additionalProperties: false" property with
>   "unevaluatedProperties: false".
> - Discard label definition from the example.
> - Align settings of the "#thermal-sensor-cells" property with two spaces
>   ahead of the property line start.
> ---
>  .../bindings/hwmon/baikal,bt1-pvt.yaml        | 95 +++++++++++++++++++
>  1 file changed, 95 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/hwmon/baikal,bt1-pvt.yaml
> 

Reviewed-by: Rob Herring <robh@kernel.org>

[PATCH v2 2/2] hwmon: Add Baikal-T1 PVT sensor driver

[Serge Semin]

Baikal-T1 SoC provides an embedded process, voltage and temperature
sensor to monitor an internal SoC environment (chip temperature, supply
voltage and process monitor) and on time detect critical situations,
which may cause the system instability and even damages. The IP-block
is based on the Analog Bits PVT sensor, but is equipped with a
dedicated control wrapper, which provides a MMIO registers-based access
to the sensor core functionality (APB3-bus based) and exposes an
additional functions like thresholds/data ready interrupts, its status
and masks, measurements timeout. All of these is used to create a hwmon
driver being added to the kernel by this commit.

The driver implements support for the hardware monitoring capabilities
of Baikal-T1 process, voltage and temperature sensors. PVT IP-core
consists of one temperature and four voltage sensors, each of which is
implemented as a dedicated hwmon channel config.

The driver can optionally provide the hwmon alarms for each sensor the
PVT controller supports. The alarms functionality is made compile-time
configurable due to the hardware interface implementation peculiarity,
which is connected with an ability to convert data from only one sensor
at a time. Additional limitation is that the controller performs the
thresholds checking synchronously with the data conversion procedure.
Due to these limitations in order to have the hwmon alarms
automatically detected the driver code must switch from one sensor to
another, read converted data and manually check the threshold status
bits. Depending on the measurements timeout settings this design may
cause additional burden on the system performance. By default if the
alarms kernel config is disabled the data conversion is performed by
the driver on demand when read operation is requested via corresponding
_input-file.

Co-developed-by: Maxim Kaurkin <maxim.kaurkin@baikalelectronics.ru>
Signed-off-by: Maxim Kaurkin <maxim.kaurkin@baikalelectronics.ru>
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Cc: Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Paul Burton <paulburton@kernel.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: linux-mips@vger.kernel.org
Cc: devicetree@vger.kernel.org

---

Changelog v2:
- Discard handwritten IO-access wrappers. Use normal readl/writel instead.
- Use generic FIELD_{GET,PREP} macros instead of handwritten ones.
- Since the driver depends on the OF config we can remove of_match_ptr()
  macro utilization.
- Don't print error-message if no platform IRQ found. Just return an error.
- Remove probe-status info string printout.
---
 Documentation/hwmon/bt1-pvt.rst |  113 +++
 drivers/hwmon/Kconfig           |   29 +
 drivers/hwmon/Makefile          |    1 +
 drivers/hwmon/bt1-pvt.c         | 1154 +++++++++++++++++++++++++++++++
 drivers/hwmon/bt1-pvt.h         |  237 +++++++
 5 files changed, 1534 insertions(+)
 create mode 100644 Documentation/hwmon/bt1-pvt.rst
 create mode 100644 drivers/hwmon/bt1-pvt.c
 create mode 100644 drivers/hwmon/bt1-pvt.h

diff --git a/Documentation/hwmon/bt1-pvt.rst b/Documentation/hwmon/bt1-pvt.rst
new file mode 100644
index 000000000000..7ad8574bce98
--- /dev/null
+++ b/Documentation/hwmon/bt1-pvt.rst
@@ -0,0 +1,113 @@
+.. SPDX-License-Identifier: GPL-2.0-only
+
+Kernel driver bt1-pvt
+=====================
+
+Supported chips:
+
+  * Baikal-T1 PVT sensor (in SoC)
+
+    Prefix: 'bt1-pvt'
+
+    Addresses scanned: -
+
+    Datasheet: Provided by BAIKAL ELECTRONICS upon request and under NDA
+
+Authors:
+    Maxim Kaurkin <maxim.kaurkin@baikalelectronics.ru>
+    Serge Semin <Sergey.Semin@baikalelectronics.ru>
+
+Description
+-----------
+
+This driver implements support for the hardware monitoring capabilities of the
+embedded into Baikal-T1 process, voltage and temperature sensors. PVT IP-core
+consists of one temperature and four voltage sensors, which can be used to
+monitor the chip internal environment like heating, supply voltage and
+transistors performance. The driver can optionally provide the hwmon alarms
+for each sensor the PVT controller supports. The alarms functionality is made
+compile-time configurable due to the hardware interface implementation
+peculiarity, which is connected with an ability to convert data from only one
+sensor at a time. Additional limitation is that the controller performs the
+thresholds checking synchronously with the data conversion procedure. Due to
+these in order to have the hwmon alarms automatically detected the driver code
+must switch from one sensor to another, read converted data and manually check
+the threshold status bits. Depending on the measurements timeout settings
+(update_interval sysfs node value) this design may cause additional burden on
+the system performance. So in case if alarms are unnecessary in your system
+design it's recommended to have them disabled to prevent the PVT IRQs being
+periodically raised to get the data cache/alarms status up to date. By default
+in alarm-less configuration the data conversion is performed by the driver
+on demand when read operation is requested via corresponding _input-file.
+
+Temperature Monitoring
+----------------------
+
+Temperature is measured with 10-bit resolution and reported in millidegree
+Celsius. The driver performs all the scaling by itself therefore reports true
+temperatures that don't need any user-space adjustments. While the data
+translation formulae isn't linear, which gives us non-linear discreteness,
+it's close to one, but giving a bit better accuracy for higher temperatures.
+The temperature input is mapped as follows (the last column indicates the input
+ranges)::
+
+	temp1: CPU embedded diode	-48.38C - +147.438C
+
+In case if the alarms kernel config is enabled in the driver the temperature input
+has associated min and max limits which trigger an alarm when crossed.
+
+Voltage Monitoring
+------------------
+
+The voltage inputs are also sampled with 10-bit resolution and reported in
+millivolts. But in this case the data translation formulae is linear, which
+provides a constant measurements discreteness. The data scaling is also
+performed by the driver, so returning true millivolts. The voltage inputs are
+mapped as follows (the last column indicates the input ranges)::
+
+	in0: VDD		(processor core)		0.62V - 1.168V
+	in1: Low-Vt		(low voltage threshold)		0.62V - 1.168V
+	in2: High-Vt		(high voltage threshold)	0.62V - 1.168V
+	in3: Standard-Vt	(standard voltage threshold)	0.62V - 1.168V
+
+In case if the alarms configis enabled in the driver the voltage inputs
+have associated min and max limits which trigger an alarm when crossed.
+
+Sysfs Attributes
+----------------
+
+Following is a list of all sysfs attributes that the driver provides, their
+permissions and a short description:
+
+=============================== ======= =======================================
+Name				Perm	Description
+=============================== ======= =======================================
+update_interval			RW	Measurements update interval per
+					sensor.
+temp1_type			RO	Sensor type (always 1 as CPU embedded
+					diode).
+temp1_label			RO	MIPS P5600 Temperature sensor.
+temp1_input			RO	Measured temperature in millidegree
+					Celsius.
+temp1_min			RW	Low limit for temp input.
+temp1_max			RW	High limit for temp input.
+temp1_min_alarm			RO	Temperature input alarm. Returns 1 if
+					temperature input went below min limit,
+					0 otherwise.
+temp1_max_alarm			RO	Temperature input alarm. Returns 1 if
+					temperature input went above max limit,
+					0 otherwise.
+temp1_trim			RW	Temperature sensor trimming factor
+					(specific to the SoC application).
+in[0-3]_label			RO	MIPS P5600 Voltage sensor (either core
+					or low/high/standard thresholds).
+in[0-3]_input			RO	Measured voltage in millivolts.
+in[0-3]_min			RW	Low limit for voltage input.
+in[0-3]_max			RW	High limit for voltage input.
+in[0-3]_min_alarm		RO	Voltage input alarm. Returns 1 if
+					voltage input went below min limit,
+					0 otherwise.
+in[0-3]_max_alarm		RO	Voltage input alarm. Returns 1 if
+					voltage input went above max limit,
+					0 otherwise.
+=============================== ======= =======================================
diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index 4c62f900bf7e..b80fc7d398c3 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -404,6 +404,35 @@ config SENSORS_ATXP1
 	  This driver can also be built as a module. If so, the module
 	  will be called atxp1.
 
+config SENSORS_BT1_PVT
+	tristate "Baikal-T1 Process, Voltage, Temperature sensor driver"
+	depends on (MIPS_BAIKAL_T1 && OF) || COMPILE_TEST
+	help
+	  If you say yes here you get support for Baikal-T1 PVT sensor
+	  embedded into the SoC.
+
+	  This driver can also be built as a module. If so, the module will be
+	  called bt1-pvt.
+
+if SENSORS_BT1_PVT
+
+config SENSORS_BT1_PVT_ALARMS
+	bool "Enable Baikal-T1 PVT sensor alarms"
+	default n
+	help
+	  Baikal-T1 PVT IP-block provides threshold registers for each
+	  supported sensor. But the corresponding interrupts might be
+	  generated by the thresholds comparator only in synchronization with
+	  a data conversion. Additionally there is only one sensor data can
+	  be converted at a time. All of these makes the interface impossible
+	  to be used for the hwmon alarms implementation without periodic
+	  switch between the PVT sensors. By default the data conversion is
+	  performed on demand from the user-space. If this config is enabled
+	  the data conversion will be periodically performed and the data will be
+	  saved in the internal driver cache.
+
+endif
+
 config SENSORS_DRIVETEMP
 	tristate "Hard disk drives with temperature sensors"
 	depends on SCSI && ATA
diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
index b0b9c8e57176..408b86a5e71d 100644
--- a/drivers/hwmon/Makefile
+++ b/drivers/hwmon/Makefile
@@ -53,6 +53,7 @@ obj-$(CONFIG_SENSORS_ASC7621)	+= asc7621.o
 obj-$(CONFIG_SENSORS_ASPEED)	+= aspeed-pwm-tacho.o
 obj-$(CONFIG_SENSORS_ATXP1)	+= atxp1.o
 obj-$(CONFIG_SENSORS_AXI_FAN_CONTROL) += axi-fan-control.o
+obj-$(CONFIG_SENSORS_BT1_PVT)	+= bt1-pvt.o
 obj-$(CONFIG_SENSORS_CORETEMP)	+= coretemp.o
 obj-$(CONFIG_SENSORS_DA9052_ADC)+= da9052-hwmon.o
 obj-$(CONFIG_SENSORS_DA9055)+= da9055-hwmon.o
diff --git a/drivers/hwmon/bt1-pvt.c b/drivers/hwmon/bt1-pvt.c
new file mode 100644
index 000000000000..1a29fd01aa2b
--- /dev/null
+++ b/drivers/hwmon/bt1-pvt.c
@@ -0,0 +1,1154 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2020 BAIKAL ELECTRONICS, JSC
+ *
+ * Authors:
+ *   Maxim Kaurkin <maxim.kaurkin@baikalelectronics.ru>
+ *   Serge Semin <Sergey.Semin@baikalelectronics.ru>
+ *
+ * Baikal-T1 Process, Voltage, Temperature sensor driver
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/bitfield.h>
+#include <linux/device.h>
+#include <linux/platform_device.h>
+#include <linux/interrupt.h>
+#include <linux/bitops.h>
+#include <linux/mutex.h>
+#include <linux/seqlock.h>
+#include <linux/completion.h>
+#include <linux/limits.h>
+#include <linux/ktime.h>
+#include <linux/clk.h>
+#include <linux/sysfs.h>
+#include <linux/hwmon.h>
+#include <linux/hwmon-sysfs.h>
+
+#include "bt1-pvt.h"
+
+/*
+ * For the sake of the code simplification we created the sensors info table
+ * with the sensor names, activation modes, threshold registers base address
+ * and the thresholds bit fields.
+ */
+static const struct pvt_sensor_info pvt_info[] = {
+	PVT_SENSOR_INFO("MIPS P5600 Temperature", "temp1", TEMP, TTHRES),
+	PVT_SENSOR_INFO("MIPS P5600 Voltage", "in0", VOLT, VTHRES),
+	PVT_SENSOR_INFO("MIPS P5600 Low-Vt", "in1", LVT, LTHRES),
+	PVT_SENSOR_INFO("MIPS P5600 High-Vt", "in2", HVT, HTHRES),
+	PVT_SENSOR_INFO("MIPS P5600 Standard-Vt", "in3", SVT, STHRES)
+};
+
+/*
+ * The original translation formulae of the temperature (in degrees of Celsius)
+ * to PVT data and vice-versa are following:
+ * N = 1.8322e-8*(T^4) + 2.343e-5*(T^3) + 8.7018e-3*(T^2) + 3.9269*(T^1) +
+ *     1.7204e2,
+ * T = -1.6743e-11*(N^4) + 8.1542e-8*(N^3) + -1.8201e-4*(N^2) +
+ *     3.1020e-1*(N^1) - 4.838e1,
+ * where T = [-48.380, 147.438]C and N = [0, 1023].
+ * They must be accordingly altered to be suitable for the integer arithmetics.
+ * The technique is called 'factor redistribution', which just makes sure the
+ * multiplications and divisions are made so to have a result of the operations
+ * within the integer numbers limit. In addition we need to translate the
+ * formulae to accept millidegrees of Celsius. Here what they look like after
+ * the alterations:
+ * N = (18322e-20*(T^4) + 2343e-13*(T^3) + 87018e-9*(T^2) + 39269e-3*T +
+ *     17204e2) / 1e4,
+ * T = -16743e-12*(D^4) + 81542e-9*(D^3) - 182010e-6*(D^2) + 310200e-3*D -
+ *     48380,
+ * where T = [-48380, 147438] mC and N = [0, 1023].
+ */
+const static struct pvt_poly poly_temp_to_N = {
+	.total_divider = 10000,
+	.terms = {
+		{4, 18322, 10000, 10000},
+		{3, 2343, 10000, 10},
+		{2, 87018, 10000, 10},
+		{1, 39269, 1000, 1},
+		{0, 1720400, 1, 1}
+	}
+};
+
+const static struct pvt_poly poly_N_to_temp = {
+	.total_divider = 1,
+	.terms = {
+		{4, -16743, 1000, 1},
+		{3, 81542, 1000, 1},
+		{2, -182010, 1000, 1},
+		{1, 310200, 1000, 1},
+		{0, -48380, 1, 1}
+	}
+};
+
+/*
+ * Similar alterations are performed for the voltage conversion equations.
+ * The original formulae are:
+ * N = 1.8658e3*V - 1.1572e3,
+ * V = (N + 1.1572e3) / 1.8658e3,
+ * where V = [0.620, 1.168] V and N = [0, 1023].
+ * After the optimization they looks as follows:
+ * N = (18658e-3*V - 11572) / 10,
+ * V = N * 10^5 / 18658 + 11572 * 10^4 / 18658.
+ */
+const static struct pvt_poly poly_volt_to_N = {
+	.total_divider = 10,
+	.terms = {
+		{1, 18658, 1000, 1},
+		{0, -11572, 1, 1}
+	}
+};
+
+const static struct pvt_poly poly_N_to_volt = {
+	.total_divider = 10,
+	.terms = {
+		{1, 100000, 18658, 1},
+		{0, 115720000, 1, 18658}
+	}
+};
+
+/*
+ * Here is the polynomial calculation function, which performs the
+ * redistributed terms calculations. It's pretty straightforward. We walk
+ * over each degree term up to the free one, and perform the redistributed
+ * multiplication of the term coefficient, its divider (as for the rationale
+ * fraction representation), data power and the rational fraction divider
+ * leftover. Then all of this is collected in a total sum variable, which
+ * value is normalized by the total divider before being returned.
+ */
+static long pvt_calc_poly(const struct pvt_poly *poly, long data)
+{
+	const struct pvt_poly_term *term = poly->terms;
+	long tmp, ret = 0;
+	int deg;
+
+	do {
+		tmp = term->coef;
+		for (deg = 0; deg < term->deg; ++deg)
+			tmp = mult_frac(tmp, data, term->divider);
+		ret += tmp / term->divider_leftover;
+	} while ((term++)->deg);
+
+	return ret / poly->total_divider;
+}
+
+static inline u32 pvt_update(void __iomem *reg, u32 mask, u32 data)
+{
+	u32 old;
+
+	old = readl_relaxed(reg);
+	writel((old & ~mask) | (data & mask), reg);
+
+	return old & mask;
+}
+
+/*
+ * Baikal-T1 PVT mode can be updated only when the controller is disabled.
+ * So first we disable it, then set the new mode together with the controller
+ * getting back enabled. The same concerns the temperature trim and
+ * measurements timeout. If it is necessary the interface mutex is supposed
+ * to be locked at the time the operations are performed.
+ */
+static inline void pvt_set_mode(struct pvt_hwmon *pvt, u32 mode)
+{
+	u32 old;
+
+	mode = FIELD_PREP(PVT_CTRL_MODE_MASK, mode);
+
+	old = pvt_update(pvt->regs + PVT_CTRL, PVT_CTRL_EN, 0);
+	pvt_update(pvt->regs + PVT_CTRL, PVT_CTRL_MODE_MASK | PVT_CTRL_EN,
+		   mode | old);
+}
+
+static inline void pvt_set_trim(struct pvt_hwmon *pvt, u32 trim)
+{
+	u32 old;
+
+	trim = FIELD_PREP(PVT_CTRL_TRIM_MASK, trim);
+
+	old = pvt_update(pvt->regs + PVT_CTRL, PVT_CTRL_EN, 0);
+	pvt_update(pvt->regs + PVT_CTRL, PVT_CTRL_TRIM_MASK | PVT_CTRL_EN,
+		   trim | old);
+}
+
+static inline void pvt_set_tout(struct pvt_hwmon *pvt, u32 tout)
+{
+	u32 old;
+
+	old = pvt_update(pvt->regs + PVT_CTRL, PVT_CTRL_EN, 0);
+	writel(tout, pvt->regs + PVT_TTIMEOUT);
+	pvt_update(pvt->regs + PVT_CTRL, PVT_CTRL_EN, old);
+}
+
+/*
+ * This driver can optionally provide the hwmon alarms for each sensor the PVT
+ * controller supports. The alarms functionality is made compile-time
+ * configurable due to the hardware interface implementation peculiarity
+ * described further in this comment. So in case if alarms are unnecessary in
+ * your system design it's recommended to have them disabled to prevent the PVT
+ * IRQs being periodically raised to get the data cache/alarms status up to
+ * date.
+ *
+ * Baikal-T1 PVT embedded controller is based on the Analog Bits PVT sensor,
+ * but is equipped with a dedicated control wrapper. It exposes the PVT
+ * sub-block registers space via the APB3 bus. In addition the wrapper provides
+ * a common interrupt vector of the sensors conversion completion events and
+ * threshold value alarms. Alas the wrapper interface hasn't been fully thought
+ * through. There is only one sensor can be activated at a time, for which the
+ * thresholds comparator is enabled right after the data conversion is
+ * completed. Due to this if alarms need to be implemented for all available
+ * sensors we can't just set the thresholds and enable the interrupts. We need
+ * to enable the sensors one after another and let the controller to detect
+ * the alarms by itself at each conversion. This also makes pointless to handle
+ * the alarms interrupts, since in occasion they happen synchronously with
+ * data conversion completion. The best driver design would be to have the
+ * completion interrupts enabled only and keep the converted value in the
+ * driver data cache. This solution is implemented if hwmon alarms are enabled
+ * in this driver. In case if the alarms are disabled, the conversion is
+ * performed on demand at the time a sensors input file is read.
+ */
+
+#if defined(CONFIG_SENSORS_BT1_PVT_ALARMS)
+
+#define pvt_hard_isr NULL
+
+static irqreturn_t pvt_soft_isr(int irq, void *data)
+{
+	const struct pvt_sensor_info *info;
+	struct pvt_hwmon *pvt = data;
+	struct pvt_cache *cache;
+	u32 val, thres_sts, old;
+
+	/*
+	 * DVALID bit will be cleared by reading the data. We need to save the
+	 * status before the next conversion happens. Threshold events will be
+	 * handled a bit later.
+	 */
+	thres_sts = readl(pvt->regs + PVT_RAW_INTR_STAT);
+
+	/*
+	 * Then lets recharge the PVT interface with the next sampling mode.
+	 * Lock the interface mutex to serialize trim, timeouts and alarm
+	 * thresholds settings.
+	 */
+	cache = &pvt->cache[pvt->sensor];
+	info = &pvt_info[pvt->sensor];
+	pvt->sensor = (pvt->sensor == PVT_SENSOR_LAST) ?
+		      PVT_SENSOR_FIRST : (pvt->sensor + 1);
+
+	/*
+	 * For some reason we have to mask the interrupt before changing the
+	 * mode, otherwise sometimes the temperature mode doesn't get
+	 * activated even though the actual mode in ctrl register correspond
+	 * to one. Then we read the data. By doing so we also recharge the data
+	 * conversion. After this the mode corresponding to the next
+	 * sensor in the row is set. Finally we enable the interrupts back.
+	 */
+	mutex_lock(&pvt->iface_mtx);
+
+	old = pvt_update(pvt->regs + PVT_INTR_MASK, PVT_INTR_DVALID,
+			 PVT_INTR_DVALID);
+
+	val = readl(pvt->regs + PVT_DATA);
+
+	pvt_set_mode(pvt, pvt_info[pvt->sensor].mode);
+
+	pvt_update(pvt->regs + PVT_INTR_MASK, PVT_INTR_DVALID, old);
+
+	mutex_unlock(&pvt->iface_mtx);
+
+	/*
+	 * We can now update the data cache with data just retrieved from the
+	 * sensor. Lock write-seqlock to make sure the reader has a coherent
+	 * data.
+	 */
+	write_seqlock(&cache->data_seqlock);
+
+	cache->data = FIELD_GET(PVT_DATA_DATA_MASK, val);
+
+	write_sequnlock(&cache->data_seqlock);
+
+	/*
+	 * While PVT core is doing the next mode data conversion, we'll check
+	 * whether the alarms were triggered for the current sensor. Note that
+	 * according to the documentation only one threshold IRQ status can be
+	 * set at a time, that's why if-else statement is utilized.
+	 */
+	if ((thres_sts & info->thres_sts_lo) ^ cache->thres_sts_lo) {
+		WRITE_ONCE(cache->thres_sts_lo, thres_sts & info->thres_sts_lo);
+		sysfs_notify(&pvt->hwmon->kobj, NULL, info->sysfs_min_alarm);
+		kobject_uevent(&pvt->hwmon->kobj, KOBJ_CHANGE);
+		if (cache->thres_sts_lo) {
+			dev_warn(pvt->dev, "%s is below the lower limit\n",
+				 info->label);
+		} else {
+			dev_warn(pvt->dev, "%s is back to normal\n",
+				 info->label);
+		}
+	} else if ((thres_sts & info->thres_sts_hi) ^ cache->thres_sts_hi) {
+		WRITE_ONCE(cache->thres_sts_hi, thres_sts & info->thres_sts_hi);
+		sysfs_notify(&pvt->hwmon->kobj, NULL, info->sysfs_max_alarm);
+		kobject_uevent(&pvt->hwmon->kobj, KOBJ_CHANGE);
+		if (cache->thres_sts_hi) {
+			dev_warn(pvt->dev, "%s is above the upper limit\n",
+				 info->label);
+		} else {
+			dev_warn(pvt->dev, "%s is back to normal\n",
+				 info->label);
+		}
+	}
+
+	return IRQ_HANDLED;
+}
+
+inline umode_t pvt_limit_is_visible(enum pvt_sensor_type type)
+{
+	return 0644;
+}
+
+inline umode_t pvt_alarm_is_visible(enum pvt_sensor_type type)
+{
+	return 0444;
+}
+
+static int pvt_read_data(struct pvt_hwmon *pvt, enum pvt_sensor_type type,
+			 long *val)
+{
+	struct pvt_cache *cache = &pvt->cache[type];
+	unsigned int seq;
+	u32 data;
+
+	do {
+		seq = read_seqbegin(&cache->data_seqlock);
+		data = cache->data;
+	} while (read_seqretry(&cache->data_seqlock, seq));
+
+	if (type == PVT_TEMP)
+		*val = pvt_calc_poly(&poly_N_to_temp, data);
+	else
+		*val = pvt_calc_poly(&poly_N_to_volt, data);
+
+	return 0;
+}
+
+static int pvt_read_limit(struct pvt_hwmon *pvt, enum pvt_sensor_type type,
+			  bool is_low, long *val)
+{
+	u32 data;
+
+	/* No need in serialization, since it is just read from MMIO. */
+	data = readl(pvt->regs + pvt_info[type].thres_base);
+
+	if (is_low)
+		data = FIELD_GET(PVT_THRES_LO_MASK, data);
+	else
+		data = FIELD_GET(PVT_THRES_HI_MASK, data);
+
+	if (type == PVT_TEMP)
+		*val = pvt_calc_poly(&poly_N_to_temp, data);
+	else
+		*val = pvt_calc_poly(&poly_N_to_volt, data);
+
+	return 0;
+}
+
+static int pvt_write_limit(struct pvt_hwmon *pvt, enum pvt_sensor_type type,
+			   bool is_low, long val)
+{
+	u32 data, limit, mask;
+	int ret;
+
+	if (type == PVT_TEMP) {
+		val = clamp(val, PVT_TEMP_MIN, PVT_TEMP_MAX);
+		data = pvt_calc_poly(&poly_temp_to_N, val);
+	} else {
+		val = clamp(val, PVT_VOLT_MIN, PVT_VOLT_MAX);
+		data = pvt_calc_poly(&poly_volt_to_N, val);
+	}
+
+	/* Serialize limit update, since a part of the register is changed. */
+	ret = mutex_lock_interruptible(&pvt->iface_mtx);
+	if (ret)
+		return ret;
+
+	/* Make sure the upper and lower ranges don't intersect. */
+	limit = readl(pvt->regs + pvt_info[type].thres_base);
+	if (is_low) {
+		limit = FIELD_GET(PVT_THRES_HI_MASK, limit);
+		data = clamp_val(data, PVT_DATA_MIN, limit);
+		data = FIELD_PREP(PVT_THRES_LO_MASK, data);
+		mask = PVT_THRES_LO_MASK;
+	} else {
+		limit = FIELD_GET(PVT_THRES_LO_MASK, limit);
+		data = clamp_val(data, limit, PVT_DATA_MAX);
+		data = FIELD_PREP(PVT_THRES_HI_MASK, data);
+		mask = PVT_THRES_HI_MASK;
+	}
+
+	pvt_update(pvt->regs + pvt_info[type].thres_base, mask, data);
+
+	mutex_unlock(&pvt->iface_mtx);
+
+	return 0;
+}
+
+static int pvt_read_alarm(struct pvt_hwmon *pvt, enum pvt_sensor_type type,
+			  bool is_low, long *val)
+{
+	if (is_low)
+		*val = !!READ_ONCE(pvt->cache[type].thres_sts_lo);
+	else
+		*val = !!READ_ONCE(pvt->cache[type].thres_sts_hi);
+
+	return 0;
+}
+
+static const struct hwmon_channel_info *pvt_channel_info[] = {
+	HWMON_CHANNEL_INFO(chip,
+			   HWMON_C_REGISTER_TZ | HWMON_C_UPDATE_INTERVAL),
+	HWMON_CHANNEL_INFO(temp,
+			   HWMON_T_INPUT | HWMON_T_TYPE | HWMON_T_LABEL |
+			   HWMON_T_MIN | HWMON_T_MIN_ALARM |
+			   HWMON_T_MAX | HWMON_T_MAX_ALARM),
+	HWMON_CHANNEL_INFO(in,
+			   HWMON_I_INPUT | HWMON_I_LABEL |
+			   HWMON_I_MIN | HWMON_I_MIN_ALARM |
+			   HWMON_I_MAX | HWMON_I_MAX_ALARM,
+			   HWMON_I_INPUT | HWMON_I_LABEL |
+			   HWMON_I_MIN | HWMON_I_MIN_ALARM |
+			   HWMON_I_MAX | HWMON_I_MAX_ALARM,
+			   HWMON_I_INPUT | HWMON_I_LABEL |
+			   HWMON_I_MIN | HWMON_I_MIN_ALARM |
+			   HWMON_I_MAX | HWMON_I_MAX_ALARM,
+			   HWMON_I_INPUT | HWMON_I_LABEL |
+			   HWMON_I_MIN | HWMON_I_MIN_ALARM |
+			   HWMON_I_MAX | HWMON_I_MAX_ALARM),
+	NULL
+};
+
+#else /* !CONFIG_SENSORS_BT1_PVT_ALARMS */
+
+static irqreturn_t pvt_hard_isr(int irq, void *data)
+{
+	struct pvt_hwmon *pvt = data;
+	struct pvt_cache *cache;
+	u32 val;
+
+	/*
+	 * Mask the DVALID interrupt so after exiting from the handler a
+	 * repeated conversion wouldn't happen.
+	 */
+	pvt_update(pvt->regs + PVT_INTR_MASK, PVT_INTR_DVALID,
+		   PVT_INTR_DVALID);
+
+	/*
+	 * Nothing special for alarm-less driver. Just read the data, update
+	 * the cache and notify a waiter of this event.
+	 */
+	val = readl(pvt->regs + PVT_DATA);
+	if (!(val & PVT_DATA_VALID)) {
+		dev_err(pvt->dev, "Got IRQ when data isn't valid\n");
+		return IRQ_HANDLED;
+	}
+
+	cache = &pvt->cache[pvt->sensor];
+
+	WRITE_ONCE(cache->data, FIELD_GET(PVT_DATA_DATA_MASK, val));
+
+	complete(&cache->conversion);
+
+	return IRQ_HANDLED;
+}
+
+#define pvt_soft_isr NULL
+
+inline umode_t pvt_limit_is_visible(enum pvt_sensor_type type)
+{
+	return 0;
+}
+
+inline umode_t pvt_alarm_is_visible(enum pvt_sensor_type type)
+{
+	return 0;
+}
+
+static int pvt_read_data(struct pvt_hwmon *pvt, enum pvt_sensor_type type,
+			 long *val)
+{
+	struct pvt_cache *cache = &pvt->cache[type];
+	u32 data;
+	int ret;
+
+	/*
+	 * Lock PVT conversion interface until data cache is updated. The
+	 * data read procedure is following: set the requested PVT sensor
+	 * mode, enable IRQ and conversion, wait until conversion is finished,
+	 * then disable conversion and IRQ, and read the cached data.
+	 */
+	ret = mutex_lock_interruptible(&pvt->iface_mtx);
+	if (ret)
+		return ret;
+
+	pvt->sensor = type;
+	pvt_set_mode(pvt, pvt_info[type].mode);
+
+	/*
+	 * Unmask the DVALID interrupt and enable the sensors conversions.
+	 * Do the reverse procedure when conversion is done.
+	 */
+	pvt_update(pvt->regs + PVT_INTR_MASK, PVT_INTR_DVALID, 0);
+	pvt_update(pvt->regs + PVT_CTRL, PVT_CTRL_EN, PVT_CTRL_EN);
+
+	wait_for_completion(&cache->conversion);
+
+	pvt_update(pvt->regs + PVT_CTRL, PVT_CTRL_EN, 0);
+	pvt_update(pvt->regs + PVT_INTR_MASK, PVT_INTR_DVALID,
+		   PVT_INTR_DVALID);
+
+	data = READ_ONCE(cache->data);
+
+	mutex_unlock(&pvt->iface_mtx);
+
+	if (type == PVT_TEMP)
+		*val = pvt_calc_poly(&poly_N_to_temp, data);
+	else
+		*val = pvt_calc_poly(&poly_N_to_volt, data);
+
+	return 0;
+}
+
+static int pvt_read_limit(struct pvt_hwmon *pvt, enum pvt_sensor_type type,
+			  bool is_low, long *val)
+{
+	return -EOPNOTSUPP;
+}
+
+static int pvt_write_limit(struct pvt_hwmon *pvt, enum pvt_sensor_type type,
+			   bool is_low, long val)
+{
+	return -EOPNOTSUPP;
+}
+
+static int pvt_read_alarm(struct pvt_hwmon *pvt, enum pvt_sensor_type type,
+			  bool is_low, long *val)
+{
+	return -EOPNOTSUPP;
+}
+
+static const struct hwmon_channel_info *pvt_channel_info[] = {
+	HWMON_CHANNEL_INFO(chip,
+			   HWMON_C_REGISTER_TZ | HWMON_C_UPDATE_INTERVAL),
+	HWMON_CHANNEL_INFO(temp,
+			   HWMON_T_INPUT | HWMON_T_TYPE | HWMON_T_LABEL),
+	HWMON_CHANNEL_INFO(in,
+			   HWMON_I_INPUT | HWMON_I_LABEL,
+			   HWMON_I_INPUT | HWMON_I_LABEL,
+			   HWMON_I_INPUT | HWMON_I_LABEL,
+			   HWMON_I_INPUT | HWMON_I_LABEL),
+	NULL
+};
+
+#endif /* !CONFIG_SENSORS_BT1_PVT_ALARMS */
+
+static inline bool pvt_hwmon_channel_is_valid(enum hwmon_sensor_types type,
+					      int ch)
+{
+	switch (type) {
+	case hwmon_temp:
+		if (ch < 0 || ch >= PVT_TEMP_CHS)
+			return false;
+		break;
+	case hwmon_in:
+		if (ch < 0 || ch >= PVT_VOLT_CHS)
+			return false;
+		break;
+	default:
+		break;
+	}
+
+	/* The rest of the types are independent from the channel number. */
+	return true;
+}
+
+static umode_t pvt_hwmon_is_visible(const void *data,
+				    enum hwmon_sensor_types type,
+				    u32 attr, int ch)
+{
+	if (!pvt_hwmon_channel_is_valid(type, ch))
+		return 0;
+
+	switch (type) {
+	case hwmon_chip:
+		switch (attr) {
+		case hwmon_chip_update_interval:
+			return 0644;
+		}
+		break;
+	case hwmon_temp:
+		switch (attr) {
+		case hwmon_temp_input:
+		case hwmon_temp_type:
+		case hwmon_temp_label:
+			return 0444;
+		case hwmon_temp_min:
+		case hwmon_temp_max:
+			return pvt_limit_is_visible(ch);
+		case hwmon_temp_min_alarm:
+		case hwmon_temp_max_alarm:
+			return pvt_alarm_is_visible(ch);
+		}
+		break;
+	case hwmon_in:
+		switch (attr) {
+		case hwmon_in_input:
+		case hwmon_in_label:
+			return 0444;
+		case hwmon_in_min:
+		case hwmon_in_max:
+			return pvt_limit_is_visible(PVT_VOLT + ch);
+		case hwmon_in_min_alarm:
+		case hwmon_in_max_alarm:
+			return pvt_alarm_is_visible(PVT_VOLT + ch);
+		}
+		break;
+	default:
+		break;
+	}
+
+	return 0;
+}
+
+static int pvt_read_timeout(struct pvt_hwmon *pvt, long *val)
+{
+	unsigned long rate;
+	ktime_t kt;
+	u32 data;
+
+	rate = clk_get_rate(pvt->clks[PVT_CLOCK_REF].clk);
+	if (!rate)
+		return -ENODEV;
+
+	/*
+	 * Don't bother with mutex here, since we just read data from MMIO.
+	 * We also have to scale the ticks timeout up to compensate the
+	 * ms-ns-data translations.
+	 */
+	data = readl(pvt->regs + PVT_TTIMEOUT) + 1;
+
+	/*
+	 * Calculate ref-clock based delay (Ttotal) between two consecutive
+	 * data samples of the same sensor. So we first must calculate the
+	 * delay introduced by the internal ref-clock timer (Tref * Fclk).
+	 * Then add the constant timeout cuased by each conversion latency
+	 * (Tmin). The basic formulae for each conversion is following:
+	 *   Ttotal = Tref * Fclk + Tmin
+	 * Note if alarms are enabled the sensors are  polled one after
+	 * another, so in order to have the delay being applicable for each
+	 * sensor the requested value must be equally redistirbuted.
+	 */
+#if defined(CONFIG_SENSORS_BT1_PVT_ALARMS)
+	kt = ktime_set(PVT_SENSORS_NUM * (u64)data, 0);
+	kt = ktime_divns(kt, rate);
+	kt = ktime_add_ns(kt, PVT_SENSORS_NUM * PVT_TOUT_MIN);
+#else
+	kt = ktime_set(data, 0);
+	kt = ktime_divns(kt, rate);
+	kt = ktime_add_ns(kt, PVT_TOUT_MIN);
+#endif
+
+	/* Return the result in msec as hwmon sysfs interface requires. */
+	*val = ktime_to_ms(kt);
+
+	return 0;
+}
+
+static int pvt_write_timeout(struct pvt_hwmon *pvt, long val)
+{
+	unsigned long rate;
+	ktime_t kt;
+	u32 data;
+	int ret;
+
+	rate = clk_get_rate(pvt->clks[PVT_CLOCK_REF].clk);
+	if (!rate)
+		return -ENODEV;
+
+	/*
+	 * If alarms are enabled, the requested timeout must be divided
+	 * between all available sensors to have the requested delay
+	 * applicable to each individual sensor.
+	 */
+	kt = ms_to_ktime(val);
+#if defined(CONFIG_SENSORS_BT1_PVT_ALARMS)
+	kt = ktime_divns(kt, PVT_SENSORS_NUM);
+#endif
+
+	/*
+	 * Subtract a constant lag, which always persists due to the limited
+	 * PVT sampling rate. Make sure the timeout is non-zero.
+	 */
+	kt = ktime_sub_ns(kt, PVT_TOUT_MIN);
+	if (ktime_to_ns(kt) < 0)
+		kt = ktime_set(0, 0);
+
+	/*
+	 * Finally recalculate the timeout in terms of the reference clock
+	 * period.
+	 */
+	data = ktime_divns(kt * rate, NSEC_PER_SEC);
+
+	/*
+	 * Update the measurements delay, but lock the interface first, since
+	 * we have to disable PVT in order to have the new delay actually
+	 * updated.
+	 */
+	ret = mutex_lock_interruptible(&pvt->iface_mtx);
+	if (ret)
+		return ret;
+
+	pvt_set_tout(pvt, data);
+
+	mutex_unlock(&pvt->iface_mtx);
+
+	return 0;
+}
+
+static int pvt_hwmon_read(struct device *dev, enum hwmon_sensor_types type,
+			  u32 attr, int ch, long *val)
+{
+	struct pvt_hwmon *pvt = dev_get_drvdata(dev);
+
+	if (!pvt_hwmon_channel_is_valid(type, ch))
+		return -EINVAL;
+
+	switch (type) {
+	case hwmon_chip:
+		switch (attr) {
+		case hwmon_chip_update_interval:
+			return pvt_read_timeout(pvt, val);
+		}
+		break;
+	case hwmon_temp:
+		switch (attr) {
+		case hwmon_temp_input:
+			return pvt_read_data(pvt, ch, val);
+		case hwmon_temp_type:
+			*val = 1;
+			return 0;
+		case hwmon_temp_min:
+			return pvt_read_limit(pvt, ch, true, val);
+		case hwmon_temp_max:
+			return pvt_read_limit(pvt, ch, false, val);
+		case hwmon_temp_min_alarm:
+			return pvt_read_alarm(pvt, ch, true, val);
+		case hwmon_temp_max_alarm:
+			return pvt_read_alarm(pvt, ch, false, val);
+		}
+		break;
+	case hwmon_in:
+		switch (attr) {
+		case hwmon_in_input:
+			return pvt_read_data(pvt, PVT_VOLT + ch, val);
+		case hwmon_in_min:
+			return pvt_read_limit(pvt, PVT_VOLT + ch, true, val);
+		case hwmon_in_max:
+			return pvt_read_limit(pvt, PVT_VOLT + ch, false, val);
+		case hwmon_in_min_alarm:
+			return pvt_read_alarm(pvt, PVT_VOLT + ch, true, val);
+		case hwmon_in_max_alarm:
+			return pvt_read_alarm(pvt, PVT_VOLT + ch, false, val);
+		}
+		break;
+	default:
+		break;
+	}
+
+	return -EOPNOTSUPP;
+}
+
+static int pvt_hwmon_read_string(struct device *dev,
+				 enum hwmon_sensor_types type,
+				 u32 attr, int ch, const char **str)
+{
+	if (!pvt_hwmon_channel_is_valid(type, ch))
+		return -EINVAL;
+
+	switch (type) {
+	case hwmon_temp:
+		switch (attr) {
+		case hwmon_temp_label:
+			*str = pvt_info[ch].label;
+			return 0;
+		}
+		break;
+	case hwmon_in:
+		switch (attr) {
+		case hwmon_in_label:
+			*str = pvt_info[PVT_VOLT + ch].label;
+			return 0;
+		}
+		break;
+	default:
+		break;
+	}
+
+	return -EOPNOTSUPP;
+}
+
+int pvt_hwmon_write(struct device *dev, enum hwmon_sensor_types type,
+		    u32 attr, int ch, long val)
+{
+	struct pvt_hwmon *pvt = dev_get_drvdata(dev);
+
+	if (!pvt_hwmon_channel_is_valid(type, ch))
+		return -EINVAL;
+
+	switch (type) {
+	case hwmon_chip:
+		switch (attr) {
+		case hwmon_chip_update_interval:
+			return pvt_write_timeout(pvt, val);
+		}
+		break;
+	case hwmon_temp:
+		switch (attr) {
+		case hwmon_temp_min:
+			return pvt_write_limit(pvt, ch, true, val);
+		case hwmon_temp_max:
+			return pvt_write_limit(pvt, ch, false, val);
+		}
+		break;
+	case hwmon_in:
+		switch (attr) {
+		case hwmon_in_min:
+			return pvt_write_limit(pvt, PVT_VOLT + ch, true, val);
+		case hwmon_in_max:
+			return pvt_write_limit(pvt, PVT_VOLT + ch, false, val);
+		}
+		break;
+	default:
+		break;
+	}
+
+	return -EOPNOTSUPP;
+}
+
+static const struct hwmon_ops pvt_hwmon_ops = {
+	.is_visible = pvt_hwmon_is_visible,
+	.read = pvt_hwmon_read,
+	.read_string = pvt_hwmon_read_string,
+	.write = pvt_hwmon_write
+};
+
+static const struct hwmon_chip_info pvt_hwmon_info = {
+	.ops = &pvt_hwmon_ops,
+	.info = pvt_channel_info
+};
+
+static ssize_t pvt_hwmon_temp_trim_show(struct device *dev,
+					struct device_attribute *attr,
+					char *buf)
+{
+	struct pvt_hwmon *pvt = dev_get_drvdata(dev);
+	u32 data;
+
+	data = readl(pvt->regs + PVT_CTRL);
+	data = FIELD_GET(PVT_CTRL_TRIM_MASK, data);
+
+	return scnprintf(buf, PAGE_SIZE, "%u\n", data);
+}
+
+static ssize_t pvt_hwmon_temp_trim_store(struct device *dev,
+					 struct device_attribute *attr,
+					 const char *buf, size_t count)
+{
+	struct pvt_hwmon *pvt = dev_get_drvdata(dev);
+	u32 data;
+	int ret;
+
+	ret = kstrtou32(buf, 0, &data);
+	if (ret)
+		return ret;
+
+	data = clamp_val(data, PVT_TRIM_MIN, PVT_TRIM_MAX);
+
+	/*
+	 * Serialize trim update, since a part of the register is changed and
+	 * the controller is supposed to be disabled during this operation.
+	 */
+	ret = mutex_lock_interruptible(&pvt->iface_mtx);
+	if (ret)
+		return ret;
+
+	pvt_set_trim(pvt, data);
+
+	mutex_unlock(&pvt->iface_mtx);
+
+	return count;
+}
+static SENSOR_DEVICE_ATTR_RW(temp1_trim, pvt_hwmon_temp_trim, 0);
+
+static struct attribute *pvt_hwmon_attrs[] = {
+	&sensor_dev_attr_temp1_trim.dev_attr.attr,
+	NULL
+};
+ATTRIBUTE_GROUPS(pvt_hwmon);
+
+static void pvt_clear_data(void *data)
+{
+	struct pvt_hwmon *pvt = data;
+#if !defined(CONFIG_SENSORS_BT1_PVT_ALARMS)
+	int idx;
+
+	for (idx = 0; idx < PVT_SENSORS_NUM; ++idx)
+		complete_all(&pvt->cache[idx].conversion);
+#endif
+
+	mutex_destroy(&pvt->iface_mtx);
+	platform_set_drvdata(to_platform_device(pvt->dev), NULL);
+}
+
+static struct pvt_hwmon *pvt_create_data(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct pvt_hwmon *pvt;
+	int ret, idx;
+
+	pvt = devm_kzalloc(dev, sizeof(*pvt), GFP_KERNEL);
+	if (!pvt)
+		return ERR_PTR(-ENOMEM);
+
+	ret = devm_add_action(dev, pvt_clear_data, pvt);
+	if (ret) {
+		dev_err(dev, "Can't add PVT data clear action\n");
+		return ERR_PTR(ret);
+	}
+
+	pvt->dev = dev;
+	pvt->sensor = PVT_SENSOR_FIRST;
+	platform_set_drvdata(pdev, pvt);
+	mutex_init(&pvt->iface_mtx);
+
+#if defined(CONFIG_SENSORS_BT1_PVT_ALARMS)
+	for (idx = 0; idx < PVT_SENSORS_NUM; ++idx)
+		seqlock_init(&pvt->cache[idx].data_seqlock);
+#else
+	for (idx = 0; idx < PVT_SENSORS_NUM; ++idx)
+		init_completion(&pvt->cache[idx].conversion);
+#endif
+
+	return pvt;
+}
+
+static int pvt_request_regs(struct pvt_hwmon *pvt)
+{
+	struct platform_device *pdev = to_platform_device(pvt->dev);
+	struct resource *res;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!res) {
+		dev_err(pvt->dev, "Couldn't find PVT memresource\n");
+		return -EINVAL;
+	}
+
+	pvt->regs = devm_ioremap_resource(pvt->dev, res);
+	if (IS_ERR(pvt->regs)) {
+		dev_err(pvt->dev, "Couldn't map PVT registers\n");
+		return PTR_ERR(pvt->regs);
+	}
+
+	return 0;
+}
+
+static void pvt_disable_clks(void *data)
+{
+	struct pvt_hwmon *pvt = data;
+
+	clk_bulk_disable_unprepare(PVT_CLOCK_NUM, pvt->clks);
+}
+
+static int pvt_request_clks(struct pvt_hwmon *pvt)
+{
+	int ret;
+
+	pvt->clks[PVT_CLOCK_APB].id = "pclk";
+	pvt->clks[PVT_CLOCK_REF].id = "ref";
+
+	ret = devm_clk_bulk_get(pvt->dev, PVT_CLOCK_NUM, pvt->clks);
+	if (ret) {
+		dev_err(pvt->dev, "Couldn't get PVT clocks descriptors\n");
+		return ret;
+	}
+
+	ret = clk_bulk_prepare_enable(PVT_CLOCK_NUM, pvt->clks);
+	if (ret) {
+		dev_err(pvt->dev, "Couldn't enable the PVT clocks\n");
+		return ret;
+	}
+
+	ret = devm_add_action_or_reset(pvt->dev, pvt_disable_clks, pvt);
+	if (ret) {
+		dev_err(pvt->dev, "Can't add PVT clocks disable action\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+static void pvt_init_iface(struct pvt_hwmon *pvt)
+{
+	/*
+	 * Make sure all interrupts and controller are disabled so not to
+	 * accidentally have ISR executed before the driver data is fully
+	 * initialized. Clear the IRQ status as well.
+	 */
+	pvt_update(pvt->regs + PVT_INTR_MASK, PVT_INTR_ALL, PVT_INTR_ALL);
+	pvt_update(pvt->regs + PVT_CTRL, PVT_CTRL_EN, 0);
+	readl(pvt->regs + PVT_CLR_INTR);
+	readl(pvt->regs + PVT_DATA);
+
+	/* Setup default sensor mode, timeout and temperature trim. */
+	pvt_set_mode(pvt, pvt_info[pvt->sensor].mode);
+	pvt_set_tout(pvt, PVT_TOUT_DEF);
+	pvt_set_trim(pvt, PVT_TRIM_DEF);
+}
+
+static int pvt_request_irq(struct pvt_hwmon *pvt)
+{
+	struct platform_device *pdev = to_platform_device(pvt->dev);
+	int ret;
+
+	pvt->irq = platform_get_irq(pdev, 0);
+	if (pvt->irq < 0)
+		return pvt->irq;
+
+	ret = devm_request_threaded_irq(pvt->dev, pvt->irq,
+					pvt_hard_isr, pvt_soft_isr,
+#if defined(CONFIG_SENSORS_BT1_PVT_ALARMS)
+					IRQF_SHARED | IRQF_TRIGGER_HIGH |
+					IRQF_ONESHOT,
+#else
+					IRQF_SHARED | IRQF_TRIGGER_HIGH,
+#endif
+					"pvt", pvt);
+	if (ret) {
+		dev_err(pvt->dev, "Couldn't request PVT IRQ\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+static int pvt_create_hwmon(struct pvt_hwmon *pvt)
+{
+	pvt->hwmon = devm_hwmon_device_register_with_info(pvt->dev,
+		dev_name(pvt->dev), pvt, &pvt_hwmon_info, pvt_hwmon_groups);
+	if (IS_ERR(pvt->hwmon)) {
+		dev_err(pvt->dev, "Couldn't create hwmon device\n");
+		return PTR_ERR(pvt->hwmon);
+	}
+
+	return 0;
+}
+
+#if defined(CONFIG_SENSORS_BT1_PVT_ALARMS)
+
+static void pvt_disable_iface(void *data)
+{
+	struct pvt_hwmon *pvt = data;
+
+	mutex_lock(&pvt->iface_mtx);
+	pvt_update(pvt->regs + PVT_CTRL, PVT_CTRL_EN, 0);
+	pvt_update(pvt->regs + PVT_INTR_MASK, PVT_INTR_DVALID,
+		   PVT_INTR_DVALID);
+	mutex_unlock(&pvt->iface_mtx);
+}
+
+static int pvt_enable_iface(struct pvt_hwmon *pvt)
+{
+	int ret;
+
+	ret = devm_add_action(pvt->dev, pvt_disable_iface, pvt);
+	if (ret) {
+		dev_err(pvt->dev, "Can't add PVT disable interface action\n");
+		return ret;
+	}
+
+	/*
+	 * Enable sensors data conversion and IRQ. We need to lock the
+	 * interface mutex since hwmon has just been created and the
+	 * corresponding sysfs files are accessible from user-space,
+	 * which theoretically may cause races.
+	 */
+	mutex_lock(&pvt->iface_mtx);
+	pvt_update(pvt->regs + PVT_INTR_MASK, PVT_INTR_DVALID, 0);
+	pvt_update(pvt->regs + PVT_CTRL, PVT_CTRL_EN, PVT_CTRL_EN);
+	mutex_unlock(&pvt->iface_mtx);
+
+	return 0;
+}
+
+#else /* !CONFIG_SENSORS_BT1_PVT_ALARMS */
+
+static int pvt_enable_iface(struct pvt_hwmon *pvt)
+{
+	return 0;
+}
+
+#endif /* !CONFIG_SENSORS_BT1_PVT_ALARMS */
+
+static int pvt_probe(struct platform_device *pdev)
+{
+	struct pvt_hwmon *pvt;
+	int ret;
+
+	pvt = pvt_create_data(pdev);
+	if (IS_ERR(pvt))
+		return PTR_ERR(pvt);
+
+	ret = pvt_request_regs(pvt);
+	if (ret)
+		return ret;
+
+	ret = pvt_request_clks(pvt);
+	if (ret)
+		return ret;
+
+	pvt_init_iface(pvt);
+
+	ret = pvt_request_irq(pvt);
+	if (ret)
+		return ret;
+
+	ret = pvt_create_hwmon(pvt);
+	if (ret)
+		return ret;
+
+	ret = pvt_enable_iface(pvt);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+static const struct of_device_id pvt_of_match[] = {
+	{ .compatible = "baikal,bt1-pvt" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, pvt_of_match);
+
+static struct platform_driver pvt_driver = {
+	.probe = pvt_probe,
+	.driver = {
+		.name = "bt1-pvt",
+		.of_match_table = pvt_of_match
+	}
+};
+module_platform_driver(pvt_driver);
+
+MODULE_AUTHOR("Maxim Kaurkin <maxim.kaurkin@baikalelectronics.ru>");
+MODULE_DESCRIPTION("Baikal-T1 PVT driver");
+MODULE_LICENSE("GPL v2");
diff --git a/drivers/hwmon/bt1-pvt.h b/drivers/hwmon/bt1-pvt.h
new file mode 100644
index 000000000000..7851ed947877
--- /dev/null
+++ b/drivers/hwmon/bt1-pvt.h
@@ -0,0 +1,237 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2020 BAIKAL ELECTRONICS, JSC
+ *
+ * Baikal-T1 Process, Voltage, Temperature sensor driver
+ */
+#ifndef __HWMON_BT1_PVT_H__
+#define __HWMON_BT1_PVT_H__
+
+#include <linux/kernel.h>
+#include <linux/platform_device.h>
+#include <linux/io.h>
+#include <linux/mutex.h>
+#include <linux/seqlock.h>
+#include <linux/completion.h>
+#include <linux/sysfs.h>
+#include <linux/hwmon.h>
+
+/* Baikal-T1 PVT registers and their bitfields */
+#define PVT_CTRL			0x00
+#define PVT_CTRL_EN			BIT(0)
+#define PVT_CTRL_MODE_FLD		1
+#define PVT_CTRL_MODE_MASK		GENMASK(3, PVT_CTRL_MODE_FLD)
+#define PVT_CTRL_MODE_TEMP		0x0
+#define PVT_CTRL_MODE_VOLT		0x1
+#define PVT_CTRL_MODE_LVT		0x2
+#define PVT_CTRL_MODE_HVT		0x4
+#define PVT_CTRL_MODE_SVT		0x6
+#define PVT_CTRL_TRIM_FLD		4
+#define PVT_CTRL_TRIM_MASK		GENMASK(8, PVT_CTRL_TRIM_FLD)
+#define PVT_DATA			0x04
+#define PVT_DATA_VALID			BIT(10)
+#define PVT_DATA_DATA_FLD		0
+#define PVT_DATA_DATA_MASK		GENMASK(9, PVT_DATA_DATA_FLD)
+#define PVT_TTHRES			0x08
+#define PVT_VTHRES			0x0C
+#define PVT_LTHRES			0x10
+#define PVT_HTHRES			0x14
+#define PVT_STHRES			0x18
+#define PVT_THRES_LO_FLD		0
+#define PVT_THRES_LO_MASK		GENMASK(9, PVT_THRES_LO_FLD)
+#define PVT_THRES_HI_FLD		10
+#define PVT_THRES_HI_MASK		GENMASK(19, PVT_THRES_HI_FLD)
+#define PVT_TTIMEOUT			0x1C
+#define PVT_INTR_STAT			0x20
+#define PVT_INTR_MASK			0x24
+#define PVT_RAW_INTR_STAT		0x28
+#define PVT_INTR_DVALID			BIT(0)
+#define PVT_INTR_TTHRES_LO		BIT(1)
+#define PVT_INTR_TTHRES_HI		BIT(2)
+#define PVT_INTR_VTHRES_LO		BIT(3)
+#define PVT_INTR_VTHRES_HI		BIT(4)
+#define PVT_INTR_LTHRES_LO		BIT(5)
+#define PVT_INTR_LTHRES_HI		BIT(6)
+#define PVT_INTR_HTHRES_LO		BIT(7)
+#define PVT_INTR_HTHRES_HI		BIT(8)
+#define PVT_INTR_STHRES_LO		BIT(9)
+#define PVT_INTR_STHRES_HI		BIT(10)
+#define PVT_INTR_ALL			GENMASK(10, 0)
+#define PVT_CLR_INTR			0x2C
+
+/*
+ * PVT sensors-related limits and default values
+ * @PVT_TEMP_MIN: Minimal temperature in millidegrees of Celsius.
+ * @PVT_TEMP_MAX: Maximal temperature in millidegrees of Celsius.
+ * @PVT_TEMP_CHS: Number of temperature hwmon channels.
+ * @PVT_VOLT_MIN: Minimal voltage in mV.
+ * @PVT_VOLT_MAX: Maximal voltage in mV.
+ * @PVT_VOLT_CHS: Number of voltage hwmon channels.
+ * @PVT_DATA_MIN: Minimal PVT raw data value.
+ * @PVT_DATA_MAX: Maximal PVT raw data value.
+ * @PVT_TRIM_MIN: Minimal temperature sensor trim value.
+ * @PVT_TRIM_MAX: Maximal temperature sensor trim value.
+ * @PVT_TRIM_DEF: Default temperature sensor trim value (set a proper value
+ *		  when one is determined for Baikal-T1 SoC).
+ * @PVT_TOUT_MIN: Minimal timeout between samples in nanoseconds.
+ * @PVT_TOUT_DEF: Default data measurements timeout. In case if alarms are
+ *		  activated the PVT IRQ is enabled to be raised after each
+ *		  conversion in order to have the thresholds checked and the
+ *		  converted value cached. Too frequent conversions may cause
+ *		  the system CPU overload. Lets set the 50ms delay between
+ *		  them by default to prevent this.
+ */
+#define PVT_TEMP_MIN		-48380L
+#define PVT_TEMP_MAX		147438L
+#define PVT_TEMP_CHS		1
+#define PVT_VOLT_MIN		620L
+#define PVT_VOLT_MAX		1168L
+#define PVT_VOLT_CHS		4
+#define PVT_DATA_MIN		0
+#define PVT_DATA_MAX		(PVT_DATA_DATA_MASK >> PVT_DATA_DATA_FLD)
+#define PVT_TRIM_MIN		0
+#define PVT_TRIM_MAX		(PVT_CTRL_TRIM_MASK >> PVT_CTRL_TRIM_FLD)
+#define PVT_TRIM_DEF		0
+#define PVT_TOUT_MIN		(NSEC_PER_SEC / 3000)
+#if defined(CONFIG_SENSORS_BT1_PVT_ALARMS)
+# define PVT_TOUT_DEF		60000
+#else
+# define PVT_TOUT_DEF		0
+#endif
+
+/*
+ * enum pvt_sensor_type - Baikal-T1 PVT sensor types (correspond to each PVT
+ *			  sampling mode)
+ * @PVT_SENSOR*: helpers to traverse the sensors in loops.
+ * @PVT_TEMP: PVT Temperature sensor.
+ * @PVT_VOLT: PVT Voltage sensor.
+ * @PVT_LVT: PVT Low-Voltage threshold sensor.
+ * @PVT_HVT: PVT High-Voltage threshold sensor.
+ * @PVT_SVT: PVT Standard-Voltage threshold sensor.
+ */
+enum pvt_sensor_type {
+	PVT_SENSOR_FIRST,
+	PVT_TEMP = PVT_SENSOR_FIRST,
+	PVT_VOLT,
+	PVT_LVT,
+	PVT_HVT,
+	PVT_SVT,
+	PVT_SENSOR_LAST = PVT_SVT,
+	PVT_SENSORS_NUM
+};
+
+/*
+ * enum pvt_clock_type - Baikal-T1 PVT clocks.
+ * @PVT_CLOCK_APB: APB clock.
+ * @PVT_CLOCK_REF: PVT reference clock.
+ */
+enum pvt_clock_type {
+	PVT_CLOCK_APB,
+	PVT_CLOCK_REF,
+	PVT_CLOCK_NUM
+};
+
+/*
+ * struct pvt_sensor_info - Baikal-T1 PVT sensor informational structure
+ * @label: hwmon sensor label.
+ * @mode: PVT mode corresponding to the channel.
+ * @thres_base: upper and lower threshold values of the sensor.
+ * @thres_sts_lo: low threshold status bitfield.
+ * @thres_sts_hi: high threshold status bitfield.
+ * @sysfs_min_alarm: pointer to a min-alarm sysfs filename.
+ * @sysfs_min_alarm: pointer to a max-alarm sysfs filename.
+ */
+struct pvt_sensor_info {
+	const char *label;
+	u32 mode;
+	unsigned long thres_base;
+	u32 thres_sts_lo;
+	u32 thres_sts_hi;
+	const char *sysfs_min_alarm;
+	const char *sysfs_max_alarm;
+};
+
+#define PVT_SENSOR_INFO(_label, _file, _mode, _thres)			\
+	{								\
+		.label = _label,					\
+		.mode = PVT_CTRL_MODE_ ##_mode,				\
+		.thres_base = PVT_ ##_thres,				\
+		.thres_sts_lo = PVT_INTR_ ##_thres## _LO,		\
+		.thres_sts_hi = PVT_INTR_ ##_thres## _HI,		\
+		.sysfs_min_alarm = _file "_min_alarm",			\
+		.sysfs_max_alarm = _file "_max_alarm"			\
+	}
+
+/*
+ * struct pvt_cache - PVT sensors data cache
+ * @data: data cache in raw format.
+ * @thres_sts_lo: low threshold status saved on the previous data conversion.
+ * @thres_sts_hi: high threshold status saved on the previous data conversion.
+ * @data_seqlock: cached data seq-lock.
+ * @conversion: data conversion completion.
+ */
+struct pvt_cache {
+	u32 data;
+#if defined(CONFIG_SENSORS_BT1_PVT_ALARMS)
+	seqlock_t data_seqlock;
+	u32 thres_sts_lo;
+	u32 thres_sts_hi;
+#else
+	struct completion conversion;
+#endif
+};
+
+/*
+ * struct pvt_hwmon - Baikal-T1 PVT private data
+ * @dev: device structure of the PVT platform device.
+ * @hwmon: hwmon device structure.
+ * @regs: pointer to the Baikal-T1 PVT registers region.
+ * @irq: PVT events IRQ number.
+ * @clks: Array of the PVT clocks descriptor (APB/ref clocks).
+ * @ref_clk: Pointer to the reference clocks descriptor.
+ * @iface_mtx: Generic interface mutex (used to lock the alarm registers
+ *	       when the alarms enabled, or the data conversion interface
+ *	       if alarms are disabled).
+ * @sensor: current PVT sensor the data conversion is being performed for.
+ * @cache: data cache descriptor.
+ */
+struct pvt_hwmon {
+	struct device *dev;
+	struct device *hwmon;
+
+	void __iomem *regs;
+	int irq;
+
+	struct clk_bulk_data clks[PVT_CLOCK_NUM];
+
+	struct mutex iface_mtx;
+	enum pvt_sensor_type sensor;
+	struct pvt_cache cache[PVT_SENSORS_NUM];
+};
+
+/*
+ * struct pvt_poly_term - a term descriptor of the PVT data translation
+ *			  polynomial
+ * @deg: degree of the term.
+ * @coef: multiplication factor of the term.
+ * @divider: distributed divider per each degree.
+ * @divider_leftover: divider leftover, which couldn't be redistributed.
+ */
+struct pvt_poly_term {
+	unsigned int deg;
+	long coef;
+	long divider;
+	long divider_leftover;
+};
+
+/*
+ * struct pvt_poly - PVT data translation polynomial descriptor
+ * @total_divider: total data divider.
+ * @terms: polynomial terms up to a free one.
+ */
+struct pvt_poly {
+	long total_divider;
+	struct pvt_poly_term terms[];
+};
+
+#endif /* __HWMON_BT1_PVT_H__ */
-- 
2.25.1

Re: [PATCH v2 2/2] hwmon: Add Baikal-T1 PVT sensor driver

[Guenter Roeck]

On Sun, May 10, 2020 at 01:32:11PM +0300, Serge Semin wrote:
> Baikal-T1 SoC provides an embedded process, voltage and temperature
> sensor to monitor an internal SoC environment (chip temperature, supply
> voltage and process monitor) and on time detect critical situations,
> which may cause the system instability and even damages. The IP-block
> is based on the Analog Bits PVT sensor, but is equipped with a
> dedicated control wrapper, which provides a MMIO registers-based access
> to the sensor core functionality (APB3-bus based) and exposes an
> additional functions like thresholds/data ready interrupts, its status
> and masks, measurements timeout. All of these is used to create a hwmon
> driver being added to the kernel by this commit.
> 
> The driver implements support for the hardware monitoring capabilities
> of Baikal-T1 process, voltage and temperature sensors. PVT IP-core
> consists of one temperature and four voltage sensors, each of which is
> implemented as a dedicated hwmon channel config.
> 
> The driver can optionally provide the hwmon alarms for each sensor the
> PVT controller supports. The alarms functionality is made compile-time
> configurable due to the hardware interface implementation peculiarity,
> which is connected with an ability to convert data from only one sensor
> at a time. Additional limitation is that the controller performs the
> thresholds checking synchronously with the data conversion procedure.
> Due to these limitations in order to have the hwmon alarms
> automatically detected the driver code must switch from one sensor to
> another, read converted data and manually check the threshold status
> bits. Depending on the measurements timeout settings this design may
> cause additional burden on the system performance. By default if the
> alarms kernel config is disabled the data conversion is performed by
> the driver on demand when read operation is requested via corresponding
> _input-file.
> 
> Co-developed-by: Maxim Kaurkin <maxim.kaurkin@baikalelectronics.ru>
> Signed-off-by: Maxim Kaurkin <maxim.kaurkin@baikalelectronics.ru>
> Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
> Cc: Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>
> Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
> Cc: Paul Burton <paulburton@kernel.org>
> Cc: Ralf Baechle <ralf@linux-mips.org>
> Cc: Arnd Bergmann <arnd@arndb.de>
> Cc: Rob Herring <robh+dt@kernel.org>
> Cc: linux-mips@vger.kernel.org
> Cc: devicetree@vger.kernel.org
> ---
> 
> Changelog v2:
> - Discard handwritten IO-access wrappers. Use normal readl/writel instead.
> - Use generic FIELD_{GET,PREP} macros instead of handwritten ones.
> - Since the driver depends on the OF config we can remove of_match_ptr()
>   macro utilization.
> - Don't print error-message if no platform IRQ found. Just return an error.
> - Remove probe-status info string printout.
> ---
>  Documentation/hwmon/bt1-pvt.rst |  113 +++

Needs to be added to index.rst.

>  drivers/hwmon/Kconfig           |   29 +
>  drivers/hwmon/Makefile          |    1 +
>  drivers/hwmon/bt1-pvt.c         | 1154 +++++++++++++++++++++++++++++++
>  drivers/hwmon/bt1-pvt.h         |  237 +++++++
>  5 files changed, 1534 insertions(+)
>  create mode 100644 Documentation/hwmon/bt1-pvt.rst
>  create mode 100644 drivers/hwmon/bt1-pvt.c
>  create mode 100644 drivers/hwmon/bt1-pvt.h
> 
> diff --git a/Documentation/hwmon/bt1-pvt.rst b/Documentation/hwmon/bt1-pvt.rst
> new file mode 100644
> index 000000000000..7ad8574bce98
> --- /dev/null
> +++ b/Documentation/hwmon/bt1-pvt.rst
> @@ -0,0 +1,113 @@
> +.. SPDX-License-Identifier: GPL-2.0-only
> +
> +Kernel driver bt1-pvt
> +=====================
> +
> +Supported chips:
> +
> +  * Baikal-T1 PVT sensor (in SoC)
> +
> +    Prefix: 'bt1-pvt'
> +
> +    Addresses scanned: -
> +
> +    Datasheet: Provided by BAIKAL ELECTRONICS upon request and under NDA
> +
> +Authors:
> +    Maxim Kaurkin <maxim.kaurkin@baikalelectronics.ru>
> +    Serge Semin <Sergey.Semin@baikalelectronics.ru>
> +
> +Description
> +-----------
> +
> +This driver implements support for the hardware monitoring capabilities of the
> +embedded into Baikal-T1 process, voltage and temperature sensors. PVT IP-core
> +consists of one temperature and four voltage sensors, which can be used to
> +monitor the chip internal environment like heating, supply voltage and
> +transistors performance. The driver can optionally provide the hwmon alarms
> +for each sensor the PVT controller supports. The alarms functionality is made
> +compile-time configurable due to the hardware interface implementation
> +peculiarity, which is connected with an ability to convert data from only one
> +sensor at a time. Additional limitation is that the controller performs the
> +thresholds checking synchronously with the data conversion procedure. Due to
> +these in order to have the hwmon alarms automatically detected the driver code
> +must switch from one sensor to another, read converted data and manually check
> +the threshold status bits. Depending on the measurements timeout settings
> +(update_interval sysfs node value) this design may cause additional burden on
> +the system performance. So in case if alarms are unnecessary in your system
> +design it's recommended to have them disabled to prevent the PVT IRQs being
> +periodically raised to get the data cache/alarms status up to date. By default
> +in alarm-less configuration the data conversion is performed by the driver
> +on demand when read operation is requested via corresponding _input-file.
> +
> +Temperature Monitoring
> +----------------------
> +
> +Temperature is measured with 10-bit resolution and reported in millidegree
> +Celsius. The driver performs all the scaling by itself therefore reports true
> +temperatures that don't need any user-space adjustments. While the data
> +translation formulae isn't linear, which gives us non-linear discreteness,
> +it's close to one, but giving a bit better accuracy for higher temperatures.
> +The temperature input is mapped as follows (the last column indicates the input
> +ranges)::
> +
> +	temp1: CPU embedded diode	-48.38C - +147.438C
> +
> +In case if the alarms kernel config is enabled in the driver the temperature input
> +has associated min and max limits which trigger an alarm when crossed.
> +
> +Voltage Monitoring
> +------------------
> +
> +The voltage inputs are also sampled with 10-bit resolution and reported in
> +millivolts. But in this case the data translation formulae is linear, which
> +provides a constant measurements discreteness. The data scaling is also
> +performed by the driver, so returning true millivolts. The voltage inputs are
> +mapped as follows (the last column indicates the input ranges)::
> +
> +	in0: VDD		(processor core)		0.62V - 1.168V
> +	in1: Low-Vt		(low voltage threshold)		0.62V - 1.168V
> +	in2: High-Vt		(high voltage threshold)	0.62V - 1.168V
> +	in3: Standard-Vt	(standard voltage threshold)	0.62V - 1.168V
> +
> +In case if the alarms configis enabled in the driver the voltage inputs
> +have associated min and max limits which trigger an alarm when crossed.
> +
> +Sysfs Attributes
> +----------------
> +
> +Following is a list of all sysfs attributes that the driver provides, their
> +permissions and a short description:
> +
> +=============================== ======= =======================================
> +Name				Perm	Description
> +=============================== ======= =======================================
> +update_interval			RW	Measurements update interval per
> +					sensor.
> +temp1_type			RO	Sensor type (always 1 as CPU embedded
> +					diode).
> +temp1_label			RO	MIPS P5600 Temperature sensor.
> +temp1_input			RO	Measured temperature in millidegree
> +					Celsius.
> +temp1_min			RW	Low limit for temp input.
> +temp1_max			RW	High limit for temp input.
> +temp1_min_alarm			RO	Temperature input alarm. Returns 1 if
> +					temperature input went below min limit,
> +					0 otherwise.
> +temp1_max_alarm			RO	Temperature input alarm. Returns 1 if
> +					temperature input went above max limit,
> +					0 otherwise.
> +temp1_trim			RW	Temperature sensor trimming factor
> +					(specific to the SoC application).

This needs a much better documentation as well as explanation why it needs to be
a sysfs attribute instead of a devicetree node (ie why it needs to be
runtime-controlled).

> +in[0-3]_label			RO	MIPS P5600 Voltage sensor (either core
> +					or low/high/standard thresholds).
> +in[0-3]_input			RO	Measured voltage in millivolts.
> +in[0-3]_min			RW	Low limit for voltage input.
> +in[0-3]_max			RW	High limit for voltage input.
> +in[0-3]_min_alarm		RO	Voltage input alarm. Returns 1 if
> +					voltage input went below min limit,
> +					0 otherwise.
> +in[0-3]_max_alarm		RO	Voltage input alarm. Returns 1 if
> +					voltage input went above max limit,
> +					0 otherwise.
> +=============================== ======= =======================================
> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> index 4c62f900bf7e..b80fc7d398c3 100644
> --- a/drivers/hwmon/Kconfig
> +++ b/drivers/hwmon/Kconfig
> @@ -404,6 +404,35 @@ config SENSORS_ATXP1
>  	  This driver can also be built as a module. If so, the module
>  	  will be called atxp1.
>  
> +config SENSORS_BT1_PVT
> +	tristate "Baikal-T1 Process, Voltage, Temperature sensor driver"
> +	depends on (MIPS_BAIKAL_T1 && OF) || COMPILE_TEST
> +	help
> +	  If you say yes here you get support for Baikal-T1 PVT sensor
> +	  embedded into the SoC.
> +
> +	  This driver can also be built as a module. If so, the module will be
> +	  called bt1-pvt.
> +
> +if SENSORS_BT1_PVT
> +
> +config SENSORS_BT1_PVT_ALARMS
> +	bool "Enable Baikal-T1 PVT sensor alarms"
> +	default n

"default n" is unnecessary. Also, instead of "if SENSORS_BT1_PVT", please
use "depends on SENSORS_BT1_PVT".

> +	help
> +	  Baikal-T1 PVT IP-block provides threshold registers for each
> +	  supported sensor. But the corresponding interrupts might be
> +	  generated by the thresholds comparator only in synchronization with
> +	  a data conversion. Additionally there is only one sensor data can
> +	  be converted at a time. All of these makes the interface impossible
> +	  to be used for the hwmon alarms implementation without periodic
> +	  switch between the PVT sensors. By default the data conversion is
> +	  performed on demand from the user-space. If this config is enabled
> +	  the data conversion will be periodically performed and the data will be
> +	  saved in the internal driver cache.
> +
> +endif
> +
>  config SENSORS_DRIVETEMP
>  	tristate "Hard disk drives with temperature sensors"
>  	depends on SCSI && ATA
> diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
> index b0b9c8e57176..408b86a5e71d 100644
> --- a/drivers/hwmon/Makefile
> +++ b/drivers/hwmon/Makefile
> @@ -53,6 +53,7 @@ obj-$(CONFIG_SENSORS_ASC7621)	+= asc7621.o
>  obj-$(CONFIG_SENSORS_ASPEED)	+= aspeed-pwm-tacho.o
>  obj-$(CONFIG_SENSORS_ATXP1)	+= atxp1.o
>  obj-$(CONFIG_SENSORS_AXI_FAN_CONTROL) += axi-fan-control.o
> +obj-$(CONFIG_SENSORS_BT1_PVT)	+= bt1-pvt.o
>  obj-$(CONFIG_SENSORS_CORETEMP)	+= coretemp.o
>  obj-$(CONFIG_SENSORS_DA9052_ADC)+= da9052-hwmon.o
>  obj-$(CONFIG_SENSORS_DA9055)+= da9055-hwmon.o
> diff --git a/drivers/hwmon/bt1-pvt.c b/drivers/hwmon/bt1-pvt.c
> new file mode 100644
> index 000000000000..1a29fd01aa2b
> --- /dev/null
> +++ b/drivers/hwmon/bt1-pvt.c
> @@ -0,0 +1,1154 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (C) 2020 BAIKAL ELECTRONICS, JSC
> + *
> + * Authors:
> + *   Maxim Kaurkin <maxim.kaurkin@baikalelectronics.ru>
> + *   Serge Semin <Sergey.Semin@baikalelectronics.ru>
> + *
> + * Baikal-T1 Process, Voltage, Temperature sensor driver
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/types.h>
> +#include <linux/bitfield.h>
> +#include <linux/device.h>
> +#include <linux/platform_device.h>
> +#include <linux/interrupt.h>
> +#include <linux/bitops.h>
> +#include <linux/mutex.h>
> +#include <linux/seqlock.h>
> +#include <linux/completion.h>
> +#include <linux/limits.h>
> +#include <linux/ktime.h>
> +#include <linux/clk.h>
> +#include <linux/sysfs.h>
> +#include <linux/hwmon.h>
> +#include <linux/hwmon-sysfs.h>

Alphabetic order, please.

> +
> +#include "bt1-pvt.h"
> +
> +/*
> + * For the sake of the code simplification we created the sensors info table
> + * with the sensor names, activation modes, threshold registers base address
> + * and the thresholds bit fields.
> + */
> +static const struct pvt_sensor_info pvt_info[] = {
> +	PVT_SENSOR_INFO("MIPS P5600 Temperature", "temp1", TEMP, TTHRES),
> +	PVT_SENSOR_INFO("MIPS P5600 Voltage", "in0", VOLT, VTHRES),
> +	PVT_SENSOR_INFO("MIPS P5600 Low-Vt", "in1", LVT, LTHRES),
> +	PVT_SENSOR_INFO("MIPS P5600 High-Vt", "in2", HVT, HTHRES),
> +	PVT_SENSOR_INFO("MIPS P5600 Standard-Vt", "in3", SVT, STHRES)
> +};
> +
> +/*
> + * The original translation formulae of the temperature (in degrees of Celsius)
> + * to PVT data and vice-versa are following:
> + * N = 1.8322e-8*(T^4) + 2.343e-5*(T^3) + 8.7018e-3*(T^2) + 3.9269*(T^1) +
> + *     1.7204e2,
> + * T = -1.6743e-11*(N^4) + 8.1542e-8*(N^3) + -1.8201e-4*(N^2) +
> + *     3.1020e-1*(N^1) - 4.838e1,
> + * where T = [-48.380, 147.438]C and N = [0, 1023].
> + * They must be accordingly altered to be suitable for the integer arithmetics.
> + * The technique is called 'factor redistribution', which just makes sure the
> + * multiplications and divisions are made so to have a result of the operations
> + * within the integer numbers limit. In addition we need to translate the
> + * formulae to accept millidegrees of Celsius. Here what they look like after
> + * the alterations:
> + * N = (18322e-20*(T^4) + 2343e-13*(T^3) + 87018e-9*(T^2) + 39269e-3*T +
> + *     17204e2) / 1e4,
> + * T = -16743e-12*(D^4) + 81542e-9*(D^3) - 182010e-6*(D^2) + 310200e-3*D -
> + *     48380,
> + * where T = [-48380, 147438] mC and N = [0, 1023].
> + */
> +const static struct pvt_poly poly_temp_to_N = {
> +	.total_divider = 10000,
> +	.terms = {
> +		{4, 18322, 10000, 10000},
> +		{3, 2343, 10000, 10},
> +		{2, 87018, 10000, 10},
> +		{1, 39269, 1000, 1},
> +		{0, 1720400, 1, 1}
> +	}
> +};
> +
> +const static struct pvt_poly poly_N_to_temp = {
> +	.total_divider = 1,
> +	.terms = {
> +		{4, -16743, 1000, 1},
> +		{3, 81542, 1000, 1},
> +		{2, -182010, 1000, 1},
> +		{1, 310200, 1000, 1},
> +		{0, -48380, 1, 1}
> +	}
> +};
> +
> +/*
> + * Similar alterations are performed for the voltage conversion equations.
> + * The original formulae are:
> + * N = 1.8658e3*V - 1.1572e3,
> + * V = (N + 1.1572e3) / 1.8658e3,
> + * where V = [0.620, 1.168] V and N = [0, 1023].
> + * After the optimization they looks as follows:
> + * N = (18658e-3*V - 11572) / 10,
> + * V = N * 10^5 / 18658 + 11572 * 10^4 / 18658.
> + */
> +const static struct pvt_poly poly_volt_to_N = {
> +	.total_divider = 10,
> +	.terms = {
> +		{1, 18658, 1000, 1},
> +		{0, -11572, 1, 1}
> +	}
> +};
> +
> +const static struct pvt_poly poly_N_to_volt = {
> +	.total_divider = 10,
> +	.terms = {
> +		{1, 100000, 18658, 1},
> +		{0, 115720000, 1, 18658}
> +	}
> +};
> +
> +/*
> + * Here is the polynomial calculation function, which performs the
> + * redistributed terms calculations. It's pretty straightforward. We walk
> + * over each degree term up to the free one, and perform the redistributed
> + * multiplication of the term coefficient, its divider (as for the rationale
> + * fraction representation), data power and the rational fraction divider
> + * leftover. Then all of this is collected in a total sum variable, which
> + * value is normalized by the total divider before being returned.
> + */
> +static long pvt_calc_poly(const struct pvt_poly *poly, long data)
> +{
> +	const struct pvt_poly_term *term = poly->terms;
> +	long tmp, ret = 0;
> +	int deg;
> +
> +	do {
> +		tmp = term->coef;
> +		for (deg = 0; deg < term->deg; ++deg)
> +			tmp = mult_frac(tmp, data, term->divider);
> +		ret += tmp / term->divider_leftover;
> +	} while ((term++)->deg);
> +
> +	return ret / poly->total_divider;
> +}
> +
> +static inline u32 pvt_update(void __iomem *reg, u32 mask, u32 data)
> +{
> +	u32 old;
> +
> +	old = readl_relaxed(reg);
> +	writel((old & ~mask) | (data & mask), reg);
> +
> +	return old & mask;
> +}
> +
> +/*
> + * Baikal-T1 PVT mode can be updated only when the controller is disabled.
> + * So first we disable it, then set the new mode together with the controller
> + * getting back enabled. The same concerns the temperature trim and
> + * measurements timeout. If it is necessary the interface mutex is supposed
> + * to be locked at the time the operations are performed.
> + */
> +static inline void pvt_set_mode(struct pvt_hwmon *pvt, u32 mode)
> +{
> +	u32 old;
> +
> +	mode = FIELD_PREP(PVT_CTRL_MODE_MASK, mode);
> +
> +	old = pvt_update(pvt->regs + PVT_CTRL, PVT_CTRL_EN, 0);
> +	pvt_update(pvt->regs + PVT_CTRL, PVT_CTRL_MODE_MASK | PVT_CTRL_EN,
> +		   mode | old);
> +}
> +
> +static inline void pvt_set_trim(struct pvt_hwmon *pvt, u32 trim)
> +{
> +	u32 old;
> +
> +	trim = FIELD_PREP(PVT_CTRL_TRIM_MASK, trim);
> +
> +	old = pvt_update(pvt->regs + PVT_CTRL, PVT_CTRL_EN, 0);
> +	pvt_update(pvt->regs + PVT_CTRL, PVT_CTRL_TRIM_MASK | PVT_CTRL_EN,
> +		   trim | old);
> +}
> +
> +static inline void pvt_set_tout(struct pvt_hwmon *pvt, u32 tout)
> +{
> +	u32 old;
> +
> +	old = pvt_update(pvt->regs + PVT_CTRL, PVT_CTRL_EN, 0);
> +	writel(tout, pvt->regs + PVT_TTIMEOUT);
> +	pvt_update(pvt->regs + PVT_CTRL, PVT_CTRL_EN, old);
> +}
> +
> +/*
> + * This driver can optionally provide the hwmon alarms for each sensor the PVT
> + * controller supports. The alarms functionality is made compile-time
> + * configurable due to the hardware interface implementation peculiarity
> + * described further in this comment. So in case if alarms are unnecessary in
> + * your system design it's recommended to have them disabled to prevent the PVT
> + * IRQs being periodically raised to get the data cache/alarms status up to
> + * date.
> + *
> + * Baikal-T1 PVT embedded controller is based on the Analog Bits PVT sensor,
> + * but is equipped with a dedicated control wrapper. It exposes the PVT
> + * sub-block registers space via the APB3 bus. In addition the wrapper provides
> + * a common interrupt vector of the sensors conversion completion events and
> + * threshold value alarms. Alas the wrapper interface hasn't been fully thought
> + * through. There is only one sensor can be activated at a time, for which the
> + * thresholds comparator is enabled right after the data conversion is
> + * completed. Due to this if alarms need to be implemented for all available
> + * sensors we can't just set the thresholds and enable the interrupts. We need
> + * to enable the sensors one after another and let the controller to detect
> + * the alarms by itself at each conversion. This also makes pointless to handle
> + * the alarms interrupts, since in occasion they happen synchronously with
> + * data conversion completion. The best driver design would be to have the
> + * completion interrupts enabled only and keep the converted value in the
> + * driver data cache. This solution is implemented if hwmon alarms are enabled
> + * in this driver. In case if the alarms are disabled, the conversion is
> + * performed on demand at the time a sensors input file is read.
> + */
> +
> +#if defined(CONFIG_SENSORS_BT1_PVT_ALARMS)
> +
> +#define pvt_hard_isr NULL
> +
> +static irqreturn_t pvt_soft_isr(int irq, void *data)
> +{
> +	const struct pvt_sensor_info *info;
> +	struct pvt_hwmon *pvt = data;
> +	struct pvt_cache *cache;
> +	u32 val, thres_sts, old;
> +
> +	/*
> +	 * DVALID bit will be cleared by reading the data. We need to save the
> +	 * status before the next conversion happens. Threshold events will be
> +	 * handled a bit later.
> +	 */
> +	thres_sts = readl(pvt->regs + PVT_RAW_INTR_STAT);
> +
> +	/*
> +	 * Then lets recharge the PVT interface with the next sampling mode.
> +	 * Lock the interface mutex to serialize trim, timeouts and alarm
> +	 * thresholds settings.
> +	 */
> +	cache = &pvt->cache[pvt->sensor];
> +	info = &pvt_info[pvt->sensor];
> +	pvt->sensor = (pvt->sensor == PVT_SENSOR_LAST) ?
> +		      PVT_SENSOR_FIRST : (pvt->sensor + 1);
> +
> +	/*
> +	 * For some reason we have to mask the interrupt before changing the
> +	 * mode, otherwise sometimes the temperature mode doesn't get
> +	 * activated even though the actual mode in ctrl register correspond
> +	 * to one. Then we read the data. By doing so we also recharge the data
> +	 * conversion. After this the mode corresponding to the next
> +	 * sensor in the row is set. Finally we enable the interrupts back.
> +	 */
> +	mutex_lock(&pvt->iface_mtx);
> +
> +	old = pvt_update(pvt->regs + PVT_INTR_MASK, PVT_INTR_DVALID,
> +			 PVT_INTR_DVALID);
> +
> +	val = readl(pvt->regs + PVT_DATA);
> +
> +	pvt_set_mode(pvt, pvt_info[pvt->sensor].mode);
> +
> +	pvt_update(pvt->regs + PVT_INTR_MASK, PVT_INTR_DVALID, old);
> +
> +	mutex_unlock(&pvt->iface_mtx);
> +
> +	/*
> +	 * We can now update the data cache with data just retrieved from the
> +	 * sensor. Lock write-seqlock to make sure the reader has a coherent
> +	 * data.
> +	 */
> +	write_seqlock(&cache->data_seqlock);
> +
> +	cache->data = FIELD_GET(PVT_DATA_DATA_MASK, val);
> +
> +	write_sequnlock(&cache->data_seqlock);
> +
> +	/*
> +	 * While PVT core is doing the next mode data conversion, we'll check
> +	 * whether the alarms were triggered for the current sensor. Note that
> +	 * according to the documentation only one threshold IRQ status can be
> +	 * set at a time, that's why if-else statement is utilized.
> +	 */
> +	if ((thres_sts & info->thres_sts_lo) ^ cache->thres_sts_lo) {
> +		WRITE_ONCE(cache->thres_sts_lo, thres_sts & info->thres_sts_lo);
> +		sysfs_notify(&pvt->hwmon->kobj, NULL, info->sysfs_min_alarm);
> +		kobject_uevent(&pvt->hwmon->kobj, KOBJ_CHANGE);
> +		if (cache->thres_sts_lo) {
> +			dev_warn(pvt->dev, "%s is below the lower limit\n",
> +				 info->label);
> +		} else {
> +			dev_warn(pvt->dev, "%s is back to normal\n",
> +				 info->label);
> +		}
> +	} else if ((thres_sts & info->thres_sts_hi) ^ cache->thres_sts_hi) {
> +		WRITE_ONCE(cache->thres_sts_hi, thres_sts & info->thres_sts_hi);
> +		sysfs_notify(&pvt->hwmon->kobj, NULL, info->sysfs_max_alarm);
> +		kobject_uevent(&pvt->hwmon->kobj, KOBJ_CHANGE);
> +		if (cache->thres_sts_hi) {
> +			dev_warn(pvt->dev, "%s is above the upper limit\n",
> +				 info->label);
> +		} else {
> +			dev_warn(pvt->dev, "%s is back to normal\n",
> +				 info->label);
> +		}
> +	}

The point of userspace notification is to let userspace deal with it.
I do not think it is a good idea to clog the kernel log with this
information. It may sound like a good idea, but in a system prone to
exceeding temperature limits all that is left in the log will be
repeated temperature warnings. Let userspace handle it, and let
userspace decide if it wants to log the events somewhere.

Also, please have a look at https://patchwork.kernel.org/patch/11277347/
and check if you can use it instead of creating notifications locally.

> +
> +	return IRQ_HANDLED;
> +}
> +
> +inline umode_t pvt_limit_is_visible(enum pvt_sensor_type type)
> +{
> +	return 0644;
> +}
> +
> +inline umode_t pvt_alarm_is_visible(enum pvt_sensor_type type)
> +{
> +	return 0444;
> +}
> +
> +static int pvt_read_data(struct pvt_hwmon *pvt, enum pvt_sensor_type type,
> +			 long *val)
> +{
> +	struct pvt_cache *cache = &pvt->cache[type];
> +	unsigned int seq;
> +	u32 data;
> +
> +	do {
> +		seq = read_seqbegin(&cache->data_seqlock);
> +		data = cache->data;
> +	} while (read_seqretry(&cache->data_seqlock, seq));
> +
> +	if (type == PVT_TEMP)
> +		*val = pvt_calc_poly(&poly_N_to_temp, data);
> +	else
> +		*val = pvt_calc_poly(&poly_N_to_volt, data);
> +
> +	return 0;
> +}
> +
> +static int pvt_read_limit(struct pvt_hwmon *pvt, enum pvt_sensor_type type,
> +			  bool is_low, long *val)
> +{
> +	u32 data;
> +
> +	/* No need in serialization, since it is just read from MMIO. */
> +	data = readl(pvt->regs + pvt_info[type].thres_base);
> +
> +	if (is_low)
> +		data = FIELD_GET(PVT_THRES_LO_MASK, data);
> +	else
> +		data = FIELD_GET(PVT_THRES_HI_MASK, data);
> +
> +	if (type == PVT_TEMP)
> +		*val = pvt_calc_poly(&poly_N_to_temp, data);
> +	else
> +		*val = pvt_calc_poly(&poly_N_to_volt, data);
> +
> +	return 0;
> +}
> +
> +static int pvt_write_limit(struct pvt_hwmon *pvt, enum pvt_sensor_type type,
> +			   bool is_low, long val)
> +{
> +	u32 data, limit, mask;
> +	int ret;
> +
> +	if (type == PVT_TEMP) {
> +		val = clamp(val, PVT_TEMP_MIN, PVT_TEMP_MAX);
> +		data = pvt_calc_poly(&poly_temp_to_N, val);
> +	} else {
> +		val = clamp(val, PVT_VOLT_MIN, PVT_VOLT_MAX);
> +		data = pvt_calc_poly(&poly_volt_to_N, val);
> +	}
> +
> +	/* Serialize limit update, since a part of the register is changed. */
> +	ret = mutex_lock_interruptible(&pvt->iface_mtx);
> +	if (ret)
> +		return ret;
> +
> +	/* Make sure the upper and lower ranges don't intersect. */
> +	limit = readl(pvt->regs + pvt_info[type].thres_base);
> +	if (is_low) {
> +		limit = FIELD_GET(PVT_THRES_HI_MASK, limit);
> +		data = clamp_val(data, PVT_DATA_MIN, limit);
> +		data = FIELD_PREP(PVT_THRES_LO_MASK, data);
> +		mask = PVT_THRES_LO_MASK;
> +	} else {
> +		limit = FIELD_GET(PVT_THRES_LO_MASK, limit);
> +		data = clamp_val(data, limit, PVT_DATA_MAX);
> +		data = FIELD_PREP(PVT_THRES_HI_MASK, data);
> +		mask = PVT_THRES_HI_MASK;
> +	}
> +
> +	pvt_update(pvt->regs + pvt_info[type].thres_base, mask, data);
> +
> +	mutex_unlock(&pvt->iface_mtx);
> +
> +	return 0;
> +}
> +
> +static int pvt_read_alarm(struct pvt_hwmon *pvt, enum pvt_sensor_type type,
> +			  bool is_low, long *val)
> +{
> +	if (is_low)
> +		*val = !!READ_ONCE(pvt->cache[type].thres_sts_lo);
> +	else
> +		*val = !!READ_ONCE(pvt->cache[type].thres_sts_hi);
> +
> +	return 0;
> +}
> +
> +static const struct hwmon_channel_info *pvt_channel_info[] = {
> +	HWMON_CHANNEL_INFO(chip,
> +			   HWMON_C_REGISTER_TZ | HWMON_C_UPDATE_INTERVAL),
> +	HWMON_CHANNEL_INFO(temp,
> +			   HWMON_T_INPUT | HWMON_T_TYPE | HWMON_T_LABEL |
> +			   HWMON_T_MIN | HWMON_T_MIN_ALARM |
> +			   HWMON_T_MAX | HWMON_T_MAX_ALARM),
> +	HWMON_CHANNEL_INFO(in,
> +			   HWMON_I_INPUT | HWMON_I_LABEL |
> +			   HWMON_I_MIN | HWMON_I_MIN_ALARM |
> +			   HWMON_I_MAX | HWMON_I_MAX_ALARM,
> +			   HWMON_I_INPUT | HWMON_I_LABEL |
> +			   HWMON_I_MIN | HWMON_I_MIN_ALARM |
> +			   HWMON_I_MAX | HWMON_I_MAX_ALARM,
> +			   HWMON_I_INPUT | HWMON_I_LABEL |
> +			   HWMON_I_MIN | HWMON_I_MIN_ALARM |
> +			   HWMON_I_MAX | HWMON_I_MAX_ALARM,
> +			   HWMON_I_INPUT | HWMON_I_LABEL |
> +			   HWMON_I_MIN | HWMON_I_MIN_ALARM |
> +			   HWMON_I_MAX | HWMON_I_MAX_ALARM),
> +	NULL
> +};
> +
> +#else /* !CONFIG_SENSORS_BT1_PVT_ALARMS */
> +
> +static irqreturn_t pvt_hard_isr(int irq, void *data)
> +{
> +	struct pvt_hwmon *pvt = data;
> +	struct pvt_cache *cache;
> +	u32 val;
> +
> +	/*
> +	 * Mask the DVALID interrupt so after exiting from the handler a
> +	 * repeated conversion wouldn't happen.
> +	 */
> +	pvt_update(pvt->regs + PVT_INTR_MASK, PVT_INTR_DVALID,
> +		   PVT_INTR_DVALID);
> +
> +	/*
> +	 * Nothing special for alarm-less driver. Just read the data, update
> +	 * the cache and notify a waiter of this event.
> +	 */
> +	val = readl(pvt->regs + PVT_DATA);
> +	if (!(val & PVT_DATA_VALID)) {
> +		dev_err(pvt->dev, "Got IRQ when data isn't valid\n");
> +		return IRQ_HANDLED;
> +	}
> +
> +	cache = &pvt->cache[pvt->sensor];
> +
> +	WRITE_ONCE(cache->data, FIELD_GET(PVT_DATA_DATA_MASK, val));
> +
> +	complete(&cache->conversion);
> +
> +	return IRQ_HANDLED;
> +}
> +
> +#define pvt_soft_isr NULL
> +
> +inline umode_t pvt_limit_is_visible(enum pvt_sensor_type type)
> +{
> +	return 0;
> +}
> +
> +inline umode_t pvt_alarm_is_visible(enum pvt_sensor_type type)
> +{
> +	return 0;
> +}
> +
> +static int pvt_read_data(struct pvt_hwmon *pvt, enum pvt_sensor_type type,
> +			 long *val)
> +{
> +	struct pvt_cache *cache = &pvt->cache[type];
> +	u32 data;
> +	int ret;
> +
> +	/*
> +	 * Lock PVT conversion interface until data cache is updated. The
> +	 * data read procedure is following: set the requested PVT sensor
> +	 * mode, enable IRQ and conversion, wait until conversion is finished,
> +	 * then disable conversion and IRQ, and read the cached data.
> +	 */
> +	ret = mutex_lock_interruptible(&pvt->iface_mtx);
> +	if (ret)
> +		return ret;
> +
> +	pvt->sensor = type;
> +	pvt_set_mode(pvt, pvt_info[type].mode);
> +
> +	/*
> +	 * Unmask the DVALID interrupt and enable the sensors conversions.
> +	 * Do the reverse procedure when conversion is done.
> +	 */
> +	pvt_update(pvt->regs + PVT_INTR_MASK, PVT_INTR_DVALID, 0);
> +	pvt_update(pvt->regs + PVT_CTRL, PVT_CTRL_EN, PVT_CTRL_EN);
> +
> +	wait_for_completion(&cache->conversion);
> +
> +	pvt_update(pvt->regs + PVT_CTRL, PVT_CTRL_EN, 0);
> +	pvt_update(pvt->regs + PVT_INTR_MASK, PVT_INTR_DVALID,
> +		   PVT_INTR_DVALID);
> +
> +	data = READ_ONCE(cache->data);
> +
> +	mutex_unlock(&pvt->iface_mtx);
> +
> +	if (type == PVT_TEMP)
> +		*val = pvt_calc_poly(&poly_N_to_temp, data);
> +	else
> +		*val = pvt_calc_poly(&poly_N_to_volt, data);
> +
> +	return 0;
> +}
> +
> +static int pvt_read_limit(struct pvt_hwmon *pvt, enum pvt_sensor_type type,
> +			  bool is_low, long *val)
> +{
> +	return -EOPNOTSUPP;
> +}
> +
> +static int pvt_write_limit(struct pvt_hwmon *pvt, enum pvt_sensor_type type,
> +			   bool is_low, long val)
> +{
> +	return -EOPNOTSUPP;
> +}
> +
> +static int pvt_read_alarm(struct pvt_hwmon *pvt, enum pvt_sensor_type type,
> +			  bool is_low, long *val)
> +{
> +	return -EOPNOTSUPP;
> +}
> +
> +static const struct hwmon_channel_info *pvt_channel_info[] = {
> +	HWMON_CHANNEL_INFO(chip,
> +			   HWMON_C_REGISTER_TZ | HWMON_C_UPDATE_INTERVAL),
> +	HWMON_CHANNEL_INFO(temp,
> +			   HWMON_T_INPUT | HWMON_T_TYPE | HWMON_T_LABEL),
> +	HWMON_CHANNEL_INFO(in,
> +			   HWMON_I_INPUT | HWMON_I_LABEL,
> +			   HWMON_I_INPUT | HWMON_I_LABEL,
> +			   HWMON_I_INPUT | HWMON_I_LABEL,
> +			   HWMON_I_INPUT | HWMON_I_LABEL),
> +	NULL
> +};
> +
> +#endif /* !CONFIG_SENSORS_BT1_PVT_ALARMS */
> +
> +static inline bool pvt_hwmon_channel_is_valid(enum hwmon_sensor_types type,
> +					      int ch)
> +{
> +	switch (type) {
> +	case hwmon_temp:
> +		if (ch < 0 || ch >= PVT_TEMP_CHS)
> +			return false;
> +		break;
> +	case hwmon_in:
> +		if (ch < 0 || ch >= PVT_VOLT_CHS)
> +			return false;
> +		break;
> +	default:
> +		break;
> +	}
> +
> +	/* The rest of the types are independent from the channel number. */
> +	return true;
> +}
> +
> +static umode_t pvt_hwmon_is_visible(const void *data,
> +				    enum hwmon_sensor_types type,
> +				    u32 attr, int ch)
> +{
> +	if (!pvt_hwmon_channel_is_valid(type, ch))
> +		return 0;
> +
> +	switch (type) {
> +	case hwmon_chip:
> +		switch (attr) {
> +		case hwmon_chip_update_interval:
> +			return 0644;
> +		}
> +		break;
> +	case hwmon_temp:
> +		switch (attr) {
> +		case hwmon_temp_input:
> +		case hwmon_temp_type:
> +		case hwmon_temp_label:
> +			return 0444;
> +		case hwmon_temp_min:
> +		case hwmon_temp_max:
> +			return pvt_limit_is_visible(ch);
> +		case hwmon_temp_min_alarm:
> +		case hwmon_temp_max_alarm:
> +			return pvt_alarm_is_visible(ch);
> +		}
> +		break;
> +	case hwmon_in:
> +		switch (attr) {
> +		case hwmon_in_input:
> +		case hwmon_in_label:
> +			return 0444;
> +		case hwmon_in_min:
> +		case hwmon_in_max:
> +			return pvt_limit_is_visible(PVT_VOLT + ch);
> +		case hwmon_in_min_alarm:
> +		case hwmon_in_max_alarm:
> +			return pvt_alarm_is_visible(PVT_VOLT + ch);
> +		}
> +		break;
> +	default:
> +		break;
> +	}
> +
> +	return 0;
> +}
> +
> +static int pvt_read_timeout(struct pvt_hwmon *pvt, long *val)
> +{
> +	unsigned long rate;
> +	ktime_t kt;
> +	u32 data;
> +
> +	rate = clk_get_rate(pvt->clks[PVT_CLOCK_REF].clk);

Is this a dynamic clock ? If not, it would be better to read its frequency once
in the probe function

> +	if (!rate)
> +		return -ENODEV;

... and return -ENODEV there if it is 0.

> +
> +	/*
> +	 * Don't bother with mutex here, since we just read data from MMIO.
> +	 * We also have to scale the ticks timeout up to compensate the
> +	 * ms-ns-data translations.
> +	 */
> +	data = readl(pvt->regs + PVT_TTIMEOUT) + 1;
> +
> +	/*
> +	 * Calculate ref-clock based delay (Ttotal) between two consecutive
> +	 * data samples of the same sensor. So we first must calculate the
> +	 * delay introduced by the internal ref-clock timer (Tref * Fclk).
> +	 * Then add the constant timeout cuased by each conversion latency
> +	 * (Tmin). The basic formulae for each conversion is following:
> +	 *   Ttotal = Tref * Fclk + Tmin
> +	 * Note if alarms are enabled the sensors are  polled one after
> +	 * another, so in order to have the delay being applicable for each
> +	 * sensor the requested value must be equally redistirbuted.
> +	 */
> +#if defined(CONFIG_SENSORS_BT1_PVT_ALARMS)
> +	kt = ktime_set(PVT_SENSORS_NUM * (u64)data, 0);
> +	kt = ktime_divns(kt, rate);
> +	kt = ktime_add_ns(kt, PVT_SENSORS_NUM * PVT_TOUT_MIN);
> +#else
> +	kt = ktime_set(data, 0);
> +	kt = ktime_divns(kt, rate);
> +	kt = ktime_add_ns(kt, PVT_TOUT_MIN);
> +#endif
> +
> +	/* Return the result in msec as hwmon sysfs interface requires. */
> +	*val = ktime_to_ms(kt);

Personally I am not sure about the value of using ktime for those
calculations, but that is your call. AFAICS ktime_to_ms() rounds down,
so I assume you understand that this can return 0.

> +
> +	return 0;
> +}
> +
> +static int pvt_write_timeout(struct pvt_hwmon *pvt, long val)
> +{
> +	unsigned long rate;
> +	ktime_t kt;
> +	u32 data;
> +	int ret;
> +
> +	rate = clk_get_rate(pvt->clks[PVT_CLOCK_REF].clk);
> +	if (!rate)
> +		return -ENODEV;
> +
> +	/*
> +	 * If alarms are enabled, the requested timeout must be divided
> +	 * between all available sensors to have the requested delay
> +	 * applicable to each individual sensor.
> +	 */
> +	kt = ms_to_ktime(val);
> +#if defined(CONFIG_SENSORS_BT1_PVT_ALARMS)
> +	kt = ktime_divns(kt, PVT_SENSORS_NUM);
> +#endif
> +
> +	/*
> +	 * Subtract a constant lag, which always persists due to the limited
> +	 * PVT sampling rate. Make sure the timeout is non-zero.
> +	 */
> +	kt = ktime_sub_ns(kt, PVT_TOUT_MIN);
> +	if (ktime_to_ns(kt) < 0)
> +		kt = ktime_set(0, 0);

Doesn't that set the timeout to 0 ? That seems to conflict with the "non-zero"
comment above. Should that be "not negative" ?

> +
> +	/*
> +	 * Finally recalculate the timeout in terms of the reference clock
> +	 * period.
> +	 */
> +	data = ktime_divns(kt * rate, NSEC_PER_SEC);
> +
> +	/*
> +	 * Update the measurements delay, but lock the interface first, since
> +	 * we have to disable PVT in order to have the new delay actually
> +	 * updated.
> +	 */
> +	ret = mutex_lock_interruptible(&pvt->iface_mtx);
> +	if (ret)
> +		return ret;
> +
> +	pvt_set_tout(pvt, data);
> +
> +	mutex_unlock(&pvt->iface_mtx);
> +
> +	return 0;
> +}
> +
> +static int pvt_hwmon_read(struct device *dev, enum hwmon_sensor_types type,
> +			  u32 attr, int ch, long *val)
> +{
> +	struct pvt_hwmon *pvt = dev_get_drvdata(dev);
> +
> +	if (!pvt_hwmon_channel_is_valid(type, ch))
> +		return -EINVAL;
> +
> +	switch (type) {
> +	case hwmon_chip:
> +		switch (attr) {
> +		case hwmon_chip_update_interval:
> +			return pvt_read_timeout(pvt, val);
> +		}
> +		break;
> +	case hwmon_temp:
> +		switch (attr) {
> +		case hwmon_temp_input:
> +			return pvt_read_data(pvt, ch, val);
> +		case hwmon_temp_type:
> +			*val = 1;
> +			return 0;
> +		case hwmon_temp_min:
> +			return pvt_read_limit(pvt, ch, true, val);
> +		case hwmon_temp_max:
> +			return pvt_read_limit(pvt, ch, false, val);
> +		case hwmon_temp_min_alarm:
> +			return pvt_read_alarm(pvt, ch, true, val);
> +		case hwmon_temp_max_alarm:
> +			return pvt_read_alarm(pvt, ch, false, val);
> +		}
> +		break;
> +	case hwmon_in:
> +		switch (attr) {
> +		case hwmon_in_input:
> +			return pvt_read_data(pvt, PVT_VOLT + ch, val);
> +		case hwmon_in_min:
> +			return pvt_read_limit(pvt, PVT_VOLT + ch, true, val);
> +		case hwmon_in_max:
> +			return pvt_read_limit(pvt, PVT_VOLT + ch, false, val);
> +		case hwmon_in_min_alarm:
> +			return pvt_read_alarm(pvt, PVT_VOLT + ch, true, val);
> +		case hwmon_in_max_alarm:
> +			return pvt_read_alarm(pvt, PVT_VOLT + ch, false, val);
> +		}
> +		break;
> +	default:
> +		break;
> +	}
> +
> +	return -EOPNOTSUPP;
> +}
> +
> +static int pvt_hwmon_read_string(struct device *dev,
> +				 enum hwmon_sensor_types type,
> +				 u32 attr, int ch, const char **str)
> +{
> +	if (!pvt_hwmon_channel_is_valid(type, ch))
> +		return -EINVAL;
> +
> +	switch (type) {
> +	case hwmon_temp:
> +		switch (attr) {
> +		case hwmon_temp_label:
> +			*str = pvt_info[ch].label;
> +			return 0;
> +		}
> +		break;
> +	case hwmon_in:
> +		switch (attr) {
> +		case hwmon_in_label:
> +			*str = pvt_info[PVT_VOLT + ch].label;
> +			return 0;
> +		}
> +		break;
> +	default:
> +		break;
> +	}
> +
> +	return -EOPNOTSUPP;
> +}
> +
> +int pvt_hwmon_write(struct device *dev, enum hwmon_sensor_types type,
> +		    u32 attr, int ch, long val)
> +{
> +	struct pvt_hwmon *pvt = dev_get_drvdata(dev);
> +
> +	if (!pvt_hwmon_channel_is_valid(type, ch))
> +		return -EINVAL;
> +
> +	switch (type) {
> +	case hwmon_chip:
> +		switch (attr) {
> +		case hwmon_chip_update_interval:
> +			return pvt_write_timeout(pvt, val);
> +		}
> +		break;
> +	case hwmon_temp:
> +		switch (attr) {
> +		case hwmon_temp_min:
> +			return pvt_write_limit(pvt, ch, true, val);
> +		case hwmon_temp_max:
> +			return pvt_write_limit(pvt, ch, false, val);
> +		}
> +		break;
> +	case hwmon_in:
> +		switch (attr) {
> +		case hwmon_in_min:
> +			return pvt_write_limit(pvt, PVT_VOLT + ch, true, val);
> +		case hwmon_in_max:
> +			return pvt_write_limit(pvt, PVT_VOLT + ch, false, val);
> +		}
> +		break;
> +	default:
> +		break;
> +	}
> +
> +	return -EOPNOTSUPP;
> +}
> +
> +static const struct hwmon_ops pvt_hwmon_ops = {
> +	.is_visible = pvt_hwmon_is_visible,
> +	.read = pvt_hwmon_read,
> +	.read_string = pvt_hwmon_read_string,
> +	.write = pvt_hwmon_write
> +};
> +
> +static const struct hwmon_chip_info pvt_hwmon_info = {
> +	.ops = &pvt_hwmon_ops,
> +	.info = pvt_channel_info
> +};
> +
> +static ssize_t pvt_hwmon_temp_trim_show(struct device *dev,
> +					struct device_attribute *attr,
> +					char *buf)
> +{
> +	struct pvt_hwmon *pvt = dev_get_drvdata(dev);
> +	u32 data;
> +
> +	data = readl(pvt->regs + PVT_CTRL);
> +	data = FIELD_GET(PVT_CTRL_TRIM_MASK, data);
> +
> +	return scnprintf(buf, PAGE_SIZE, "%u\n", data);
> +}
> +
> +static ssize_t pvt_hwmon_temp_trim_store(struct device *dev,
> +					 struct device_attribute *attr,
> +					 const char *buf, size_t count)
> +{
> +	struct pvt_hwmon *pvt = dev_get_drvdata(dev);
> +	u32 data;
> +	int ret;
> +
> +	ret = kstrtou32(buf, 0, &data);
> +	if (ret)
> +		return ret;
> +
> +	data = clamp_val(data, PVT_TRIM_MIN, PVT_TRIM_MAX);
> +
> +	/*
> +	 * Serialize trim update, since a part of the register is changed and
> +	 * the controller is supposed to be disabled during this operation.
> +	 */
> +	ret = mutex_lock_interruptible(&pvt->iface_mtx);
> +	if (ret)
> +		return ret;
> +
> +	pvt_set_trim(pvt, data);
> +
> +	mutex_unlock(&pvt->iface_mtx);
> +
> +	return count;
> +}
> +static SENSOR_DEVICE_ATTR_RW(temp1_trim, pvt_hwmon_temp_trim, 0);
> +
> +static struct attribute *pvt_hwmon_attrs[] = {
> +	&sensor_dev_attr_temp1_trim.dev_attr.attr,
> +	NULL
> +};
> +ATTRIBUTE_GROUPS(pvt_hwmon);
> +
> +static void pvt_clear_data(void *data)
> +{
> +	struct pvt_hwmon *pvt = data;
> +#if !defined(CONFIG_SENSORS_BT1_PVT_ALARMS)
> +	int idx;
> +
> +	for (idx = 0; idx < PVT_SENSORS_NUM; ++idx)
> +		complete_all(&pvt->cache[idx].conversion);
> +#endif
> +
> +	mutex_destroy(&pvt->iface_mtx);
> +	platform_set_drvdata(to_platform_device(pvt->dev), NULL);

Unnecessary.

> +}
> +
> +static struct pvt_hwmon *pvt_create_data(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct pvt_hwmon *pvt;
> +	int ret, idx;
> +
> +	pvt = devm_kzalloc(dev, sizeof(*pvt), GFP_KERNEL);
> +	if (!pvt)
> +		return ERR_PTR(-ENOMEM);
> +
> +	ret = devm_add_action(dev, pvt_clear_data, pvt);
> +	if (ret) {
> +		dev_err(dev, "Can't add PVT data clear action\n");
> +		return ERR_PTR(ret);
> +	}
> +
> +	pvt->dev = dev;
> +	pvt->sensor = PVT_SENSOR_FIRST;
> +	platform_set_drvdata(pdev, pvt);

I don't immediately see where this is used. Can you point to it ?

> +	mutex_init(&pvt->iface_mtx);
> +
> +#if defined(CONFIG_SENSORS_BT1_PVT_ALARMS)
> +	for (idx = 0; idx < PVT_SENSORS_NUM; ++idx)
> +		seqlock_init(&pvt->cache[idx].data_seqlock);
> +#else
> +	for (idx = 0; idx < PVT_SENSORS_NUM; ++idx)
> +		init_completion(&pvt->cache[idx].conversion);
> +#endif
> +
> +	return pvt;
> +}
> +
> +static int pvt_request_regs(struct pvt_hwmon *pvt)
> +{
> +	struct platform_device *pdev = to_platform_device(pvt->dev);
> +	struct resource *res;
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	if (!res) {
> +		dev_err(pvt->dev, "Couldn't find PVT memresource\n");
> +		return -EINVAL;
> +	}
> +
> +	pvt->regs = devm_ioremap_resource(pvt->dev, res);
> +	if (IS_ERR(pvt->regs)) {
> +		dev_err(pvt->dev, "Couldn't map PVT registers\n");
> +		return PTR_ERR(pvt->regs);
> +	}
> +
> +	return 0;
> +}
> +
> +static void pvt_disable_clks(void *data)
> +{
> +	struct pvt_hwmon *pvt = data;
> +
> +	clk_bulk_disable_unprepare(PVT_CLOCK_NUM, pvt->clks);
> +}
> +
> +static int pvt_request_clks(struct pvt_hwmon *pvt)
> +{
> +	int ret;
> +
> +	pvt->clks[PVT_CLOCK_APB].id = "pclk";
> +	pvt->clks[PVT_CLOCK_REF].id = "ref";
> +
> +	ret = devm_clk_bulk_get(pvt->dev, PVT_CLOCK_NUM, pvt->clks);
> +	if (ret) {
> +		dev_err(pvt->dev, "Couldn't get PVT clocks descriptors\n");
> +		return ret;
> +	}
> +
> +	ret = clk_bulk_prepare_enable(PVT_CLOCK_NUM, pvt->clks);
> +	if (ret) {
> +		dev_err(pvt->dev, "Couldn't enable the PVT clocks\n");
> +		return ret;
> +	}
> +
> +	ret = devm_add_action_or_reset(pvt->dev, pvt_disable_clks, pvt);
> +	if (ret) {
> +		dev_err(pvt->dev, "Can't add PVT clocks disable action\n");
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static void pvt_init_iface(struct pvt_hwmon *pvt)
> +{
> +	/*
> +	 * Make sure all interrupts and controller are disabled so not to
> +	 * accidentally have ISR executed before the driver data is fully
> +	 * initialized. Clear the IRQ status as well.
> +	 */
> +	pvt_update(pvt->regs + PVT_INTR_MASK, PVT_INTR_ALL, PVT_INTR_ALL);
> +	pvt_update(pvt->regs + PVT_CTRL, PVT_CTRL_EN, 0);
> +	readl(pvt->regs + PVT_CLR_INTR);
> +	readl(pvt->regs + PVT_DATA);
> +
> +	/* Setup default sensor mode, timeout and temperature trim. */
> +	pvt_set_mode(pvt, pvt_info[pvt->sensor].mode);
> +	pvt_set_tout(pvt, PVT_TOUT_DEF);
> +	pvt_set_trim(pvt, PVT_TRIM_DEF);
> +}
> +
> +static int pvt_request_irq(struct pvt_hwmon *pvt)
> +{
> +	struct platform_device *pdev = to_platform_device(pvt->dev);
> +	int ret;
> +
> +	pvt->irq = platform_get_irq(pdev, 0);
> +	if (pvt->irq < 0)
> +		return pvt->irq;
> +
> +	ret = devm_request_threaded_irq(pvt->dev, pvt->irq,
> +					pvt_hard_isr, pvt_soft_isr,
> +#if defined(CONFIG_SENSORS_BT1_PVT_ALARMS)
> +					IRQF_SHARED | IRQF_TRIGGER_HIGH |
> +					IRQF_ONESHOT,
> +#else
> +					IRQF_SHARED | IRQF_TRIGGER_HIGH,
> +#endif
> +					"pvt", pvt);
> +	if (ret) {
> +		dev_err(pvt->dev, "Couldn't request PVT IRQ\n");
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static int pvt_create_hwmon(struct pvt_hwmon *pvt)
> +{
> +	pvt->hwmon = devm_hwmon_device_register_with_info(pvt->dev,
> +		dev_name(pvt->dev), pvt, &pvt_hwmon_info, pvt_hwmon_groups);

Is the device name guaranteed to be a valid hwmon device name ?

> +	if (IS_ERR(pvt->hwmon)) {
> +		dev_err(pvt->dev, "Couldn't create hwmon device\n");
> +		return PTR_ERR(pvt->hwmon);
> +	}
> +
> +	return 0;
> +}
> +
> +#if defined(CONFIG_SENSORS_BT1_PVT_ALARMS)
> +
> +static void pvt_disable_iface(void *data)
> +{
> +	struct pvt_hwmon *pvt = data;
> +
> +	mutex_lock(&pvt->iface_mtx);
> +	pvt_update(pvt->regs + PVT_CTRL, PVT_CTRL_EN, 0);
> +	pvt_update(pvt->regs + PVT_INTR_MASK, PVT_INTR_DVALID,
> +		   PVT_INTR_DVALID);
> +	mutex_unlock(&pvt->iface_mtx);
> +}
> +
> +static int pvt_enable_iface(struct pvt_hwmon *pvt)
> +{
> +	int ret;
> +
> +	ret = devm_add_action(pvt->dev, pvt_disable_iface, pvt);
> +	if (ret) {
> +		dev_err(pvt->dev, "Can't add PVT disable interface action\n");
> +		return ret;
> +	}
> +
> +	/*
> +	 * Enable sensors data conversion and IRQ. We need to lock the
> +	 * interface mutex since hwmon has just been created and the
> +	 * corresponding sysfs files are accessible from user-space,
> +	 * which theoretically may cause races.
> +	 */

What if those userspace actions make a request which requires an interrupt ?

> +	mutex_lock(&pvt->iface_mtx);
> +	pvt_update(pvt->regs + PVT_INTR_MASK, PVT_INTR_DVALID, 0);
> +	pvt_update(pvt->regs + PVT_CTRL, PVT_CTRL_EN, PVT_CTRL_EN);
> +	mutex_unlock(&pvt->iface_mtx);
> +
> +	return 0;
> +}
> +
> +#else /* !CONFIG_SENSORS_BT1_PVT_ALARMS */
> +
> +static int pvt_enable_iface(struct pvt_hwmon *pvt)
> +{
> +	return 0;
> +}
> +
> +#endif /* !CONFIG_SENSORS_BT1_PVT_ALARMS */
> +
> +static int pvt_probe(struct platform_device *pdev)
> +{
> +	struct pvt_hwmon *pvt;
> +	int ret;
> +
> +	pvt = pvt_create_data(pdev);
> +	if (IS_ERR(pvt))
> +		return PTR_ERR(pvt);
> +
> +	ret = pvt_request_regs(pvt);
> +	if (ret)
> +		return ret;
> +
> +	ret = pvt_request_clks(pvt);
> +	if (ret)
> +		return ret;
> +
> +	pvt_init_iface(pvt);
> +
> +	ret = pvt_request_irq(pvt);
> +	if (ret)
> +		return ret;
> +
> +	ret = pvt_create_hwmon(pvt);
> +	if (ret)
> +		return ret;
> +
> +	ret = pvt_enable_iface(pvt);
> +	if (ret)
> +		return ret;
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id pvt_of_match[] = {
> +	{ .compatible = "baikal,bt1-pvt" },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(of, pvt_of_match);
> +
> +static struct platform_driver pvt_driver = {
> +	.probe = pvt_probe,
> +	.driver = {
> +		.name = "bt1-pvt",
> +		.of_match_table = pvt_of_match
> +	}
> +};
> +module_platform_driver(pvt_driver);
> +
> +MODULE_AUTHOR("Maxim Kaurkin <maxim.kaurkin@baikalelectronics.ru>");
> +MODULE_DESCRIPTION("Baikal-T1 PVT driver");
> +MODULE_LICENSE("GPL v2");
> diff --git a/drivers/hwmon/bt1-pvt.h b/drivers/hwmon/bt1-pvt.h
> new file mode 100644
> index 000000000000..7851ed947877
> --- /dev/null
> +++ b/drivers/hwmon/bt1-pvt.h
> @@ -0,0 +1,237 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Copyright (C) 2020 BAIKAL ELECTRONICS, JSC
> + *
> + * Baikal-T1 Process, Voltage, Temperature sensor driver
> + */
> +#ifndef __HWMON_BT1_PVT_H__
> +#define __HWMON_BT1_PVT_H__
> +
> +#include <linux/kernel.h>
> +#include <linux/platform_device.h>
> +#include <linux/io.h>
> +#include <linux/mutex.h>
> +#include <linux/seqlock.h>
> +#include <linux/completion.h>
> +#include <linux/sysfs.h>
> +#include <linux/hwmon.h>

Alphabetic order, please, and drop unnecessary includes.

> +
> +/* Baikal-T1 PVT registers and their bitfields */
> +#define PVT_CTRL			0x00
> +#define PVT_CTRL_EN			BIT(0)
> +#define PVT_CTRL_MODE_FLD		1
> +#define PVT_CTRL_MODE_MASK		GENMASK(3, PVT_CTRL_MODE_FLD)
> +#define PVT_CTRL_MODE_TEMP		0x0
> +#define PVT_CTRL_MODE_VOLT		0x1
> +#define PVT_CTRL_MODE_LVT		0x2
> +#define PVT_CTRL_MODE_HVT		0x4
> +#define PVT_CTRL_MODE_SVT		0x6
> +#define PVT_CTRL_TRIM_FLD		4
> +#define PVT_CTRL_TRIM_MASK		GENMASK(8, PVT_CTRL_TRIM_FLD)
> +#define PVT_DATA			0x04
> +#define PVT_DATA_VALID			BIT(10)
> +#define PVT_DATA_DATA_FLD		0
> +#define PVT_DATA_DATA_MASK		GENMASK(9, PVT_DATA_DATA_FLD)
> +#define PVT_TTHRES			0x08
> +#define PVT_VTHRES			0x0C
> +#define PVT_LTHRES			0x10
> +#define PVT_HTHRES			0x14
> +#define PVT_STHRES			0x18
> +#define PVT_THRES_LO_FLD		0
> +#define PVT_THRES_LO_MASK		GENMASK(9, PVT_THRES_LO_FLD)
> +#define PVT_THRES_HI_FLD		10
> +#define PVT_THRES_HI_MASK		GENMASK(19, PVT_THRES_HI_FLD)
> +#define PVT_TTIMEOUT			0x1C
> +#define PVT_INTR_STAT			0x20
> +#define PVT_INTR_MASK			0x24
> +#define PVT_RAW_INTR_STAT		0x28
> +#define PVT_INTR_DVALID			BIT(0)
> +#define PVT_INTR_TTHRES_LO		BIT(1)
> +#define PVT_INTR_TTHRES_HI		BIT(2)
> +#define PVT_INTR_VTHRES_LO		BIT(3)
> +#define PVT_INTR_VTHRES_HI		BIT(4)
> +#define PVT_INTR_LTHRES_LO		BIT(5)
> +#define PVT_INTR_LTHRES_HI		BIT(6)
> +#define PVT_INTR_HTHRES_LO		BIT(7)
> +#define PVT_INTR_HTHRES_HI		BIT(8)
> +#define PVT_INTR_STHRES_LO		BIT(9)
> +#define PVT_INTR_STHRES_HI		BIT(10)
> +#define PVT_INTR_ALL			GENMASK(10, 0)
> +#define PVT_CLR_INTR			0x2C
> +
> +/*
> + * PVT sensors-related limits and default values
> + * @PVT_TEMP_MIN: Minimal temperature in millidegrees of Celsius.
> + * @PVT_TEMP_MAX: Maximal temperature in millidegrees of Celsius.
> + * @PVT_TEMP_CHS: Number of temperature hwmon channels.
> + * @PVT_VOLT_MIN: Minimal voltage in mV.
> + * @PVT_VOLT_MAX: Maximal voltage in mV.
> + * @PVT_VOLT_CHS: Number of voltage hwmon channels.
> + * @PVT_DATA_MIN: Minimal PVT raw data value.
> + * @PVT_DATA_MAX: Maximal PVT raw data value.
> + * @PVT_TRIM_MIN: Minimal temperature sensor trim value.
> + * @PVT_TRIM_MAX: Maximal temperature sensor trim value.
> + * @PVT_TRIM_DEF: Default temperature sensor trim value (set a proper value
> + *		  when one is determined for Baikal-T1 SoC).
> + * @PVT_TOUT_MIN: Minimal timeout between samples in nanoseconds.
> + * @PVT_TOUT_DEF: Default data measurements timeout. In case if alarms are
> + *		  activated the PVT IRQ is enabled to be raised after each
> + *		  conversion in order to have the thresholds checked and the
> + *		  converted value cached. Too frequent conversions may cause
> + *		  the system CPU overload. Lets set the 50ms delay between
> + *		  them by default to prevent this.
> + */
> +#define PVT_TEMP_MIN		-48380L
> +#define PVT_TEMP_MAX		147438L
> +#define PVT_TEMP_CHS		1
> +#define PVT_VOLT_MIN		620L
> +#define PVT_VOLT_MAX		1168L
> +#define PVT_VOLT_CHS		4
> +#define PVT_DATA_MIN		0
> +#define PVT_DATA_MAX		(PVT_DATA_DATA_MASK >> PVT_DATA_DATA_FLD)
> +#define PVT_TRIM_MIN		0
> +#define PVT_TRIM_MAX		(PVT_CTRL_TRIM_MASK >> PVT_CTRL_TRIM_FLD)
> +#define PVT_TRIM_DEF		0
> +#define PVT_TOUT_MIN		(NSEC_PER_SEC / 3000)
> +#if defined(CONFIG_SENSORS_BT1_PVT_ALARMS)
> +# define PVT_TOUT_DEF		60000
> +#else
> +# define PVT_TOUT_DEF		0
> +#endif
> +
> +/*
> + * enum pvt_sensor_type - Baikal-T1 PVT sensor types (correspond to each PVT
> + *			  sampling mode)
> + * @PVT_SENSOR*: helpers to traverse the sensors in loops.
> + * @PVT_TEMP: PVT Temperature sensor.
> + * @PVT_VOLT: PVT Voltage sensor.
> + * @PVT_LVT: PVT Low-Voltage threshold sensor.
> + * @PVT_HVT: PVT High-Voltage threshold sensor.
> + * @PVT_SVT: PVT Standard-Voltage threshold sensor.
> + */
> +enum pvt_sensor_type {
> +	PVT_SENSOR_FIRST,
> +	PVT_TEMP = PVT_SENSOR_FIRST,
> +	PVT_VOLT,
> +	PVT_LVT,
> +	PVT_HVT,
> +	PVT_SVT,
> +	PVT_SENSOR_LAST = PVT_SVT,
> +	PVT_SENSORS_NUM
> +};
> +
> +/*
> + * enum pvt_clock_type - Baikal-T1 PVT clocks.
> + * @PVT_CLOCK_APB: APB clock.
> + * @PVT_CLOCK_REF: PVT reference clock.
> + */
> +enum pvt_clock_type {
> +	PVT_CLOCK_APB,
> +	PVT_CLOCK_REF,
> +	PVT_CLOCK_NUM
> +};
> +
> +/*
> + * struct pvt_sensor_info - Baikal-T1 PVT sensor informational structure
> + * @label: hwmon sensor label.
> + * @mode: PVT mode corresponding to the channel.
> + * @thres_base: upper and lower threshold values of the sensor.
> + * @thres_sts_lo: low threshold status bitfield.
> + * @thres_sts_hi: high threshold status bitfield.
> + * @sysfs_min_alarm: pointer to a min-alarm sysfs filename.
> + * @sysfs_min_alarm: pointer to a max-alarm sysfs filename.
> + */
> +struct pvt_sensor_info {
> +	const char *label;
> +	u32 mode;
> +	unsigned long thres_base;
> +	u32 thres_sts_lo;
> +	u32 thres_sts_hi;
> +	const char *sysfs_min_alarm;
> +	const char *sysfs_max_alarm;
> +};
> +
> +#define PVT_SENSOR_INFO(_label, _file, _mode, _thres)			\

_file seems to be a global define or variable, or at least checkpatch
complains about its use.

> +	{								\
> +		.label = _label,					\
> +		.mode = PVT_CTRL_MODE_ ##_mode,				\
> +		.thres_base = PVT_ ##_thres,				\
> +		.thres_sts_lo = PVT_INTR_ ##_thres## _LO,		\
> +		.thres_sts_hi = PVT_INTR_ ##_thres## _HI,		\
> +		.sysfs_min_alarm = _file "_min_alarm",			\
> +		.sysfs_max_alarm = _file "_max_alarm"			\
> +	}
> +
> +/*
> + * struct pvt_cache - PVT sensors data cache
> + * @data: data cache in raw format.
> + * @thres_sts_lo: low threshold status saved on the previous data conversion.
> + * @thres_sts_hi: high threshold status saved on the previous data conversion.
> + * @data_seqlock: cached data seq-lock.
> + * @conversion: data conversion completion.
> + */
> +struct pvt_cache {
> +	u32 data;
> +#if defined(CONFIG_SENSORS_BT1_PVT_ALARMS)
> +	seqlock_t data_seqlock;
> +	u32 thres_sts_lo;
> +	u32 thres_sts_hi;
> +#else
> +	struct completion conversion;
> +#endif
> +};
> +
> +/*
> + * struct pvt_hwmon - Baikal-T1 PVT private data
> + * @dev: device structure of the PVT platform device.
> + * @hwmon: hwmon device structure.
> + * @regs: pointer to the Baikal-T1 PVT registers region.
> + * @irq: PVT events IRQ number.
> + * @clks: Array of the PVT clocks descriptor (APB/ref clocks).
> + * @ref_clk: Pointer to the reference clocks descriptor.
> + * @iface_mtx: Generic interface mutex (used to lock the alarm registers
> + *	       when the alarms enabled, or the data conversion interface
> + *	       if alarms are disabled).
> + * @sensor: current PVT sensor the data conversion is being performed for.
> + * @cache: data cache descriptor.
> + */
> +struct pvt_hwmon {
> +	struct device *dev;
> +	struct device *hwmon;
> +
> +	void __iomem *regs;
> +	int irq;
> +
> +	struct clk_bulk_data clks[PVT_CLOCK_NUM];
> +
> +	struct mutex iface_mtx;
> +	enum pvt_sensor_type sensor;
> +	struct pvt_cache cache[PVT_SENSORS_NUM];
> +};
> +
> +/*
> + * struct pvt_poly_term - a term descriptor of the PVT data translation
> + *			  polynomial
> + * @deg: degree of the term.
> + * @coef: multiplication factor of the term.
> + * @divider: distributed divider per each degree.
> + * @divider_leftover: divider leftover, which couldn't be redistributed.
> + */
> +struct pvt_poly_term {
> +	unsigned int deg;
> +	long coef;
> +	long divider;
> +	long divider_leftover;
> +};
> +
> +/*
> + * struct pvt_poly - PVT data translation polynomial descriptor
> + * @total_divider: total data divider.
> + * @terms: polynomial terms up to a free one.
> + */
> +struct pvt_poly {
> +	long total_divider;
> +	struct pvt_poly_term terms[];
> +};
> +
> +#endif /* __HWMON_BT1_PVT_H__ */

Re: [PATCH v2 2/2] hwmon: Add Baikal-T1 PVT sensor driver

[Serge Semin]

On Fri, May 22, 2020 at 07:19:55AM -0700, Guenter Roeck wrote:
> On Sun, May 10, 2020 at 01:32:11PM +0300, Serge Semin wrote:
> > Baikal-T1 SoC provides an embedded process, voltage and temperature
> > sensor to monitor an internal SoC environment (chip temperature, supply
> > voltage and process monitor) and on time detect critical situations,
> > which may cause the system instability and even damages. The IP-block
> > is based on the Analog Bits PVT sensor, but is equipped with a
> > dedicated control wrapper, which provides a MMIO registers-based access
> > to the sensor core functionality (APB3-bus based) and exposes an
> > additional functions like thresholds/data ready interrupts, its status
> > and masks, measurements timeout. All of these is used to create a hwmon
> > driver being added to the kernel by this commit.
> > 
> > The driver implements support for the hardware monitoring capabilities
> > of Baikal-T1 process, voltage and temperature sensors. PVT IP-core
> > consists of one temperature and four voltage sensors, each of which is
> > implemented as a dedicated hwmon channel config.
> > 
> > The driver can optionally provide the hwmon alarms for each sensor the
> > PVT controller supports. The alarms functionality is made compile-time
> > configurable due to the hardware interface implementation peculiarity,
> > which is connected with an ability to convert data from only one sensor
> > at a time. Additional limitation is that the controller performs the
> > thresholds checking synchronously with the data conversion procedure.
> > Due to these limitations in order to have the hwmon alarms
> > automatically detected the driver code must switch from one sensor to
> > another, read converted data and manually check the threshold status
> > bits. Depending on the measurements timeout settings this design may
> > cause additional burden on the system performance. By default if the
> > alarms kernel config is disabled the data conversion is performed by
> > the driver on demand when read operation is requested via corresponding
> > _input-file.
> > 
> > Co-developed-by: Maxim Kaurkin <maxim.kaurkin@baikalelectronics.ru>
> > Signed-off-by: Maxim Kaurkin <maxim.kaurkin@baikalelectronics.ru>
> > Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
> > Cc: Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>
> > Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
> > Cc: Paul Burton <paulburton@kernel.org>
> > Cc: Ralf Baechle <ralf@linux-mips.org>
> > Cc: Arnd Bergmann <arnd@arndb.de>
> > Cc: Rob Herring <robh+dt@kernel.org>
> > Cc: linux-mips@vger.kernel.org
> > Cc: devicetree@vger.kernel.org
> > ---
> > 
> > Changelog v2:
> > - Discard handwritten IO-access wrappers. Use normal readl/writel instead.
> > - Use generic FIELD_{GET,PREP} macros instead of handwritten ones.
> > - Since the driver depends on the OF config we can remove of_match_ptr()
> >   macro utilization.
> > - Don't print error-message if no platform IRQ found. Just return an error.
> > - Remove probe-status info string printout.
> > ---
> >  Documentation/hwmon/bt1-pvt.rst |  113 +++
> 

> Needs to be added to index.rst.

Ok.

> 
> >  drivers/hwmon/Kconfig           |   29 +
> >  drivers/hwmon/Makefile          |    1 +
> >  drivers/hwmon/bt1-pvt.c         | 1154 +++++++++++++++++++++++++++++++
> >  drivers/hwmon/bt1-pvt.h         |  237 +++++++
> >  5 files changed, 1534 insertions(+)
> >  create mode 100644 Documentation/hwmon/bt1-pvt.rst
> >  create mode 100644 drivers/hwmon/bt1-pvt.c
> >  create mode 100644 drivers/hwmon/bt1-pvt.h
> > 
> > diff --git a/Documentation/hwmon/bt1-pvt.rst b/Documentation/hwmon/bt1-pvt.rst
> > new file mode 100644
> > index 000000000000..7ad8574bce98
> > --- /dev/null
> > +++ b/Documentation/hwmon/bt1-pvt.rst
> > @@ -0,0 +1,113 @@
> > +.. SPDX-License-Identifier: GPL-2.0-only
> > +
> > +

[nip]

> > +Sysfs Attributes
> > +----------------
> > +
> > +Following is a list of all sysfs attributes that the driver provides, their
> > +permissions and a short description:
> > +
> > +=============================== ======= =======================================
> > +Name				Perm	Description
> > +=============================== ======= =======================================
> > +update_interval			RW	Measurements update interval per
> > +					sensor.
> > +temp1_type			RO	Sensor type (always 1 as CPU embedded
> > +					diode).
> > +temp1_label			RO	MIPS P5600 Temperature sensor.
> > +temp1_input			RO	Measured temperature in millidegree
> > +					Celsius.
> > +temp1_min			RW	Low limit for temp input.
> > +temp1_max			RW	High limit for temp input.
> > +temp1_min_alarm			RO	Temperature input alarm. Returns 1 if
> > +					temperature input went below min limit,
> > +					0 otherwise.
> > +temp1_max_alarm			RO	Temperature input alarm. Returns 1 if
> > +					temperature input went above max limit,
> > +					0 otherwise.

> > +temp1_trim			RW	Temperature sensor trimming factor
> > +					(specific to the SoC application).
> 

> This needs a much better documentation as well as explanation why it needs to be
> a sysfs attribute instead of a devicetree node (ie why it needs to be
> runtime-controlled).

Trimming factor can be used to manually tune the temperature sensor characteristics
(simple speaking shifts one with respect to the base range limits) in case if in
accordance to some more reliable source of the temperature measurements, they
don't correspond to the real core temperature.

In my opinion, it would be better to have both sysfs node and DT property. The former
will be used to select a proper value at run-time when the system engineer finds
out the temperature sensor lies regarding the real core temperature. So by
picking up a proper trim value, one will make sure the sensor shows a real
temperature in accordance with a reliable reference device measurements. Then
the later (DT property) can be used to fix the determined trim value to the
particular platform configuration in the DTS file of the corresponding board.

Additionally if there is no way to alter the DT file, but a user needs to tune
the temperature sensor measurements up, then sysfs interface will be the only
way to do so.

I can also improve the description like this:

-temp1_trim			RW	Temperature sensor trimming factor
-					(specific to the SoC application).
+temp1_trim			RW	Temperature sensor trimming factor
+					can be used to manually tune the
+					absolute temperature measurements up.

What do you think about new description and having both sysf node and DT
property to set the temperature trim value?

> 
> > +in[0-3]_label			RO	MIPS P5600 Voltage sensor (either core
> > +					or low/high/standard thresholds).
> > +in[0-3]_input			RO	Measured voltage in millivolts.
> > +in[0-3]_min			RW	Low limit for voltage input.
> > +in[0-3]_max			RW	High limit for voltage input.
> > +in[0-3]_min_alarm		RO	Voltage input alarm. Returns 1 if
> > +					voltage input went below min limit,
> > +					0 otherwise.
> > +in[0-3]_max_alarm		RO	Voltage input alarm. Returns 1 if
> > +					voltage input went above max limit,
> > +					0 otherwise.
> > +=============================== ======= =======================================
> > diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> > index 4c62f900bf7e..b80fc7d398c3 100644
> > --- a/drivers/hwmon/Kconfig
> > +++ b/drivers/hwmon/Kconfig
> > @@ -404,6 +404,35 @@ config SENSORS_ATXP1
> >  	  This driver can also be built as a module. If so, the module
> >  	  will be called atxp1.
> >  
> > +config SENSORS_BT1_PVT
> > +	tristate "Baikal-T1 Process, Voltage, Temperature sensor driver"
> > +	depends on (MIPS_BAIKAL_T1 && OF) || COMPILE_TEST
> > +	help
> > +	  If you say yes here you get support for Baikal-T1 PVT sensor
> > +	  embedded into the SoC.
> > +
> > +	  This driver can also be built as a module. If so, the module will be
> > +	  called bt1-pvt.
> > +
> > +if SENSORS_BT1_PVT
> > +
> > +config SENSORS_BT1_PVT_ALARMS
> > +	bool "Enable Baikal-T1 PVT sensor alarms"
> > +	default n
> 

> "default n" is unnecessary. Also, instead of "if SENSORS_BT1_PVT", please
> use "depends on SENSORS_BT1_PVT".

Ok.

> 
> > +	help
> > +	  Baikal-T1 PVT IP-block provides threshold registers for each
> > +	  supported sensor. But the corresponding interrupts might be
> > +	  generated by the thresholds comparator only in synchronization with
> > +	  a data conversion. Additionally there is only one sensor data can
> > +	  be converted at a time. All of these makes the interface impossible
> > +	  to be used for the hwmon alarms implementation without periodic
> > +	  switch between the PVT sensors. By default the data conversion is
> > +	  performed on demand from the user-space. If this config is enabled
> > +	  the data conversion will be periodically performed and the data will be
> > +	  saved in the internal driver cache.
> > +
> > +endif
> > +
> >  config SENSORS_DRIVETEMP
> >  	tristate "Hard disk drives with temperature sensors"
> >  	depends on SCSI && ATA
> > diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
> > index b0b9c8e57176..408b86a5e71d 100644
> > --- a/drivers/hwmon/Makefile
> > +++ b/drivers/hwmon/Makefile
> > @@ -53,6 +53,7 @@ obj-$(CONFIG_SENSORS_ASC7621)	+= asc7621.o
> >  obj-$(CONFIG_SENSORS_ASPEED)	+= aspeed-pwm-tacho.o
> >  obj-$(CONFIG_SENSORS_ATXP1)	+= atxp1.o
> >  obj-$(CONFIG_SENSORS_AXI_FAN_CONTROL) += axi-fan-control.o
> > +obj-$(CONFIG_SENSORS_BT1_PVT)	+= bt1-pvt.o
> >  obj-$(CONFIG_SENSORS_CORETEMP)	+= coretemp.o
> >  obj-$(CONFIG_SENSORS_DA9052_ADC)+= da9052-hwmon.o
> >  obj-$(CONFIG_SENSORS_DA9055)+= da9055-hwmon.o
> > diff --git a/drivers/hwmon/bt1-pvt.c b/drivers/hwmon/bt1-pvt.c
> > new file mode 100644
> > index 000000000000..1a29fd01aa2b
> > --- /dev/null
> > +++ b/drivers/hwmon/bt1-pvt.c
> > @@ -0,0 +1,1154 @@
> > +// SPDX-License-Identifier: GPL-2.0-only
> > +/*
> > + * Copyright (C) 2020 BAIKAL ELECTRONICS, JSC
> > + *
> > + * Authors:
> > + *   Maxim Kaurkin <maxim.kaurkin@baikalelectronics.ru>
> > + *   Serge Semin <Sergey.Semin@baikalelectronics.ru>
> > + *
> > + * Baikal-T1 Process, Voltage, Temperature sensor driver
> > + */
> > +
> > +#include <linux/kernel.h>
> > +#include <linux/module.h>
> > +#include <linux/types.h>
> > +#include <linux/bitfield.h>
> > +#include <linux/device.h>
> > +#include <linux/platform_device.h>
> > +#include <linux/interrupt.h>
> > +#include <linux/bitops.h>
> > +#include <linux/mutex.h>
> > +#include <linux/seqlock.h>
> > +#include <linux/completion.h>
> > +#include <linux/limits.h>
> > +#include <linux/ktime.h>
> > +#include <linux/clk.h>
> > +#include <linux/sysfs.h>
> > +#include <linux/hwmon.h>
> > +#include <linux/hwmon-sysfs.h>
> 

> Alphabetic order, please.

Ok.

> 
> > +
> > +#include "bt1-pvt.h"
> > +

[nip]

> > +
> > +static irqreturn_t pvt_soft_isr(int irq, void *data)
> > +{
> > +	const struct pvt_sensor_info *info;
> > +	struct pvt_hwmon *pvt = data;
> > +	struct pvt_cache *cache;
> > +	u32 val, thres_sts, old;
> > +
> > +	/*
> > +	 * DVALID bit will be cleared by reading the data. We need to save the
> > +	 * status before the next conversion happens. Threshold events will be
> > +	 * handled a bit later.
> > +	 */
> > +	thres_sts = readl(pvt->regs + PVT_RAW_INTR_STAT);
> > +
> > +	/*
> > +	 * Then lets recharge the PVT interface with the next sampling mode.
> > +	 * Lock the interface mutex to serialize trim, timeouts and alarm
> > +	 * thresholds settings.
> > +	 */
> > +	cache = &pvt->cache[pvt->sensor];
> > +	info = &pvt_info[pvt->sensor];
> > +	pvt->sensor = (pvt->sensor == PVT_SENSOR_LAST) ?
> > +		      PVT_SENSOR_FIRST : (pvt->sensor + 1);
> > +
> > +	/*
> > +	 * For some reason we have to mask the interrupt before changing the
> > +	 * mode, otherwise sometimes the temperature mode doesn't get
> > +	 * activated even though the actual mode in ctrl register correspond
> > +	 * to one. Then we read the data. By doing so we also recharge the data
> > +	 * conversion. After this the mode corresponding to the next
> > +	 * sensor in the row is set. Finally we enable the interrupts back.
> > +	 */
> > +	mutex_lock(&pvt->iface_mtx);
> > +
> > +	old = pvt_update(pvt->regs + PVT_INTR_MASK, PVT_INTR_DVALID,
> > +			 PVT_INTR_DVALID);
> > +
> > +	val = readl(pvt->regs + PVT_DATA);
> > +
> > +	pvt_set_mode(pvt, pvt_info[pvt->sensor].mode);
> > +
> > +	pvt_update(pvt->regs + PVT_INTR_MASK, PVT_INTR_DVALID, old);
> > +
> > +	mutex_unlock(&pvt->iface_mtx);
> > +
> > +	/*
> > +	 * We can now update the data cache with data just retrieved from the
> > +	 * sensor. Lock write-seqlock to make sure the reader has a coherent
> > +	 * data.
> > +	 */
> > +	write_seqlock(&cache->data_seqlock);
> > +
> > +	cache->data = FIELD_GET(PVT_DATA_DATA_MASK, val);
> > +
> > +	write_sequnlock(&cache->data_seqlock);
> > +
> > +	/*
> > +	 * While PVT core is doing the next mode data conversion, we'll check
> > +	 * whether the alarms were triggered for the current sensor. Note that
> > +	 * according to the documentation only one threshold IRQ status can be
> > +	 * set at a time, that's why if-else statement is utilized.
> > +	 */
> > +	if ((thres_sts & info->thres_sts_lo) ^ cache->thres_sts_lo) {
> > +		WRITE_ONCE(cache->thres_sts_lo, thres_sts & info->thres_sts_lo);
> > +		sysfs_notify(&pvt->hwmon->kobj, NULL, info->sysfs_min_alarm);
> > +		kobject_uevent(&pvt->hwmon->kobj, KOBJ_CHANGE);
> > +		if (cache->thres_sts_lo) {
> > +			dev_warn(pvt->dev, "%s is below the lower limit\n",
> > +				 info->label);
> > +		} else {
> > +			dev_warn(pvt->dev, "%s is back to normal\n",
> > +				 info->label);
> > +		}
> > +	} else if ((thres_sts & info->thres_sts_hi) ^ cache->thres_sts_hi) {
> > +		WRITE_ONCE(cache->thres_sts_hi, thres_sts & info->thres_sts_hi);
> > +		sysfs_notify(&pvt->hwmon->kobj, NULL, info->sysfs_max_alarm);
> > +		kobject_uevent(&pvt->hwmon->kobj, KOBJ_CHANGE);
> > +		if (cache->thres_sts_hi) {
> > +			dev_warn(pvt->dev, "%s is above the upper limit\n",
> > +				 info->label);
> > +		} else {
> > +			dev_warn(pvt->dev, "%s is back to normal\n",
> > +				 info->label);
> > +		}
> > +	}
> 
> The point of userspace notification is to let userspace deal with it.
> I do not think it is a good idea to clog the kernel log with this
> information. It may sound like a good idea, but in a system prone to
> exceeding temperature limits all that is left in the log will be
> repeated temperature warnings. Let userspace handle it, and let
> userspace decide if it wants to log the events somewhere.

Agreed. I'll remove the warnings.

> 
> Also, please have a look at https://patchwork.kernel.org/patch/11277347/
> and check if you can use it instead of creating notifications locally.

Seems reasonable. I'll apply that patch in my tree before the patches from this
series, then use the hwmon_notify_event() to notify all the required objects at
once instead of manually pushing the notification to each of them. After a smoke
tests I'll resend the series together with your patch being initial.

Note. I will have to fix the patch a bit, since:
1) It's been created a half year ago, so there are tiny merge conflicts with
kernel 5.7-rcX.
2) hwmon_notify_event() is a bit incorrect in the incrementing channel for the
hwmon_in. It's applicable for the sattr, but not for hwmon_thermal_notify().

If I find anything else, I'll add an info about it into the patch changelog.

> 
> > +
> > +	return IRQ_HANDLED;
> > +}
> > +

[nip]

> > +
> > +static int pvt_read_timeout(struct pvt_hwmon *pvt, long *val)
> > +{
> > +	unsigned long rate;
> > +	ktime_t kt;
> > +	u32 data;
> > +
> > +	rate = clk_get_rate(pvt->clks[PVT_CLOCK_REF].clk);
> 
> Is this a dynamic clock ? If not, it would be better to read its frequency once
> in the probe function

No, It's not dynamic. I can do as you say, though in fact there is no much point
in it. The clock doesn't have the  CLK_GET_RATE_NOCACHE flag set. Then calling
clk_get_rate() will have nearly the same performance as reading from the locally
defined reference clock frequency variable except a single lock/unlock preformed
and a few conditional statements. If I had CLK_GET_RATE_NOCACHE flag set, then
the clocks would have been dynamic and I would have had to use clk_get_rate()
here anyway. So caching the reference clock value in the PVT private data won't
change much, but will add a redundant abstraction.

So I have to ask back, are you really sure that moving the clk_get_rate() into the
probe will make the situation better? If you still think so and my reasoning didn't
change your mind, please say so explicitly.

> 
> > +	if (!rate)
> > +		return -ENODEV;
> 
> ... and return -ENODEV there if it is 0

Please, see my answer above.

> 
> > +
> > +	/*
> > +	 * Don't bother with mutex here, since we just read data from MMIO.
> > +	 * We also have to scale the ticks timeout up to compensate the
> > +	 * ms-ns-data translations.
> > +	 */
> > +	data = readl(pvt->regs + PVT_TTIMEOUT) + 1;
> > +
> > +	/*
> > +	 * Calculate ref-clock based delay (Ttotal) between two consecutive
> > +	 * data samples of the same sensor. So we first must calculate the
> > +	 * delay introduced by the internal ref-clock timer (Tref * Fclk).
> > +	 * Then add the constant timeout cuased by each conversion latency
> > +	 * (Tmin). The basic formulae for each conversion is following:
> > +	 *   Ttotal = Tref * Fclk + Tmin
> > +	 * Note if alarms are enabled the sensors are  polled one after
> > +	 * another, so in order to have the delay being applicable for each
> > +	 * sensor the requested value must be equally redistirbuted.
> > +	 */
> > +#if defined(CONFIG_SENSORS_BT1_PVT_ALARMS)
> > +	kt = ktime_set(PVT_SENSORS_NUM * (u64)data, 0);
> > +	kt = ktime_divns(kt, rate);
> > +	kt = ktime_add_ns(kt, PVT_SENSORS_NUM * PVT_TOUT_MIN);
> > +#else
> > +	kt = ktime_set(data, 0);
> > +	kt = ktime_divns(kt, rate);
> > +	kt = ktime_add_ns(kt, PVT_TOUT_MIN);
> > +#endif
> > +
> > +	/* Return the result in msec as hwmon sysfs interface requires. */
> > +	*val = ktime_to_ms(kt);
> 

> Personally I am not sure about the value of using ktime for those
> calculations, but that is your call.

ktime provides a very convenient and self-explanatory interface. So instead of
dividing, adding, multiplying, sec<->msec factoring, avoiding overflows, etc,
I can do this by using a well-defined ktime interface.

> AFAICS ktime_to_ms() rounds down,
> so I assume you understand that this can return 0.

Yeah. There is no problem with it here. It's just a value returned to the
user-space. We are also ok with getting zero from user-space, since in fact
there is always 1/3000 sec conversion lag. So even if user-space asks to set
zero update interval, it will be 333 usec and we don't get the IRQs flood.

> 
> > +
> > +	return 0;
> > +}
> > +
> > +static int pvt_write_timeout(struct pvt_hwmon *pvt, long val)
> > +{
> > +	unsigned long rate;
> > +	ktime_t kt;
> > +	u32 data;
> > +	int ret;
> > +
> > +	rate = clk_get_rate(pvt->clks[PVT_CLOCK_REF].clk);
> > +	if (!rate)
> > +		return -ENODEV;
> > +
> > +	/*
> > +	 * If alarms are enabled, the requested timeout must be divided
> > +	 * between all available sensors to have the requested delay
> > +	 * applicable to each individual sensor.
> > +	 */
> > +	kt = ms_to_ktime(val);
> > +#if defined(CONFIG_SENSORS_BT1_PVT_ALARMS)
> > +	kt = ktime_divns(kt, PVT_SENSORS_NUM);
> > +#endif
> > +

> > +	/*
> > +	 * Subtract a constant lag, which always persists due to the limited
> > +	 * PVT sampling rate. Make sure the timeout is non-zero.
> > +	 */
> > +	kt = ktime_sub_ns(kt, PVT_TOUT_MIN);
> > +	if (ktime_to_ns(kt) < 0)
> > +		kt = ktime_set(0, 0);
> 
> Doesn't that set the timeout to 0 ? That seems to conflict with the "non-zero"
> comment above. Should that be "not negative" ?

Right. It should have been "not negative". Thanks for noticing this.

> 
> > +
> > +	/*
> > +	 * Finally recalculate the timeout in terms of the reference clock
> > +	 * period.
> > +	 */
> > +	data = ktime_divns(kt * rate, NSEC_PER_SEC);
> > +
> > +	/*
> > +	 * Update the measurements delay, but lock the interface first, since
> > +	 * we have to disable PVT in order to have the new delay actually
> > +	 * updated.
> > +	 */
> > +	ret = mutex_lock_interruptible(&pvt->iface_mtx);
> > +	if (ret)
> > +		return ret;
> > +
> > +	pvt_set_tout(pvt, data);
> > +
> > +	mutex_unlock(&pvt->iface_mtx);
> > +
> > +	return 0;
> > +}
> > +

[nip]

> > +
> > +static void pvt_clear_data(void *data)
> > +{
> > +	struct pvt_hwmon *pvt = data;
> > +#if !defined(CONFIG_SENSORS_BT1_PVT_ALARMS)
> > +	int idx;
> > +
> > +	for (idx = 0; idx < PVT_SENSORS_NUM; ++idx)
> > +		complete_all(&pvt->cache[idx].conversion);
> > +#endif
> > +
> > +	mutex_destroy(&pvt->iface_mtx);
> > +	platform_set_drvdata(to_platform_device(pvt->dev), NULL);
> 

> Unnecessary.

Ok.

> 
> > +}
> > +
> > +static struct pvt_hwmon *pvt_create_data(struct platform_device *pdev)
> > +{
> > +	struct device *dev = &pdev->dev;
> > +	struct pvt_hwmon *pvt;
> > +	int ret, idx;
> > +
> > +	pvt = devm_kzalloc(dev, sizeof(*pvt), GFP_KERNEL);
> > +	if (!pvt)
> > +		return ERR_PTR(-ENOMEM);
> > +
> > +	ret = devm_add_action(dev, pvt_clear_data, pvt);
> > +	if (ret) {
> > +		dev_err(dev, "Can't add PVT data clear action\n");
> > +		return ERR_PTR(ret);
> > +	}
> > +
> > +	pvt->dev = dev;
> > +	pvt->sensor = PVT_SENSOR_FIRST;
> > +	platform_set_drvdata(pdev, pvt);
> 
> I don't immediately see where this is used. Can you point to it ?

Because there is no use of it. I'll remove this setting. Thanks.

> 
> > +	mutex_init(&pvt->iface_mtx);
> > +
> > +#if defined(CONFIG_SENSORS_BT1_PVT_ALARMS)
> > +	for (idx = 0; idx < PVT_SENSORS_NUM; ++idx)
> > +		seqlock_init(&pvt->cache[idx].data_seqlock);
> > +#else
> > +	for (idx = 0; idx < PVT_SENSORS_NUM; ++idx)
> > +		init_completion(&pvt->cache[idx].conversion);
> > +#endif
> > +
> > +	return pvt;
> > +}
> > +

[nip]

> > +
> > +static int pvt_create_hwmon(struct pvt_hwmon *pvt)
> > +{
> > +	pvt->hwmon = devm_hwmon_device_register_with_info(pvt->dev,
> > +		dev_name(pvt->dev), pvt, &pvt_hwmon_info, pvt_hwmon_groups);
> 
> Is the device name guaranteed to be a valid hwmon device name ?

Hm, According to the DT convention it may have dashes, which AFAICS isn't valid
hwmon device name. I'll replace dev_name() here with a string literal like
"pvt". Is it ok to have several hwmon devices with the same name?

> 
> > +	if (IS_ERR(pvt->hwmon)) {
> > +		dev_err(pvt->dev, "Couldn't create hwmon device\n");
> > +		return PTR_ERR(pvt->hwmon);
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +#if defined(CONFIG_SENSORS_BT1_PVT_ALARMS)
> > +
> > +static void pvt_disable_iface(void *data)
> > +{
> > +	struct pvt_hwmon *pvt = data;
> > +
> > +	mutex_lock(&pvt->iface_mtx);
> > +	pvt_update(pvt->regs + PVT_CTRL, PVT_CTRL_EN, 0);
> > +	pvt_update(pvt->regs + PVT_INTR_MASK, PVT_INTR_DVALID,
> > +		   PVT_INTR_DVALID);
> > +	mutex_unlock(&pvt->iface_mtx);
> > +}
> > +
> > +static int pvt_enable_iface(struct pvt_hwmon *pvt)
> > +{
> > +	int ret;
> > +
> > +	ret = devm_add_action(pvt->dev, pvt_disable_iface, pvt);
> > +	if (ret) {
> > +		dev_err(pvt->dev, "Can't add PVT disable interface action\n");
> > +		return ret;
> > +	}
> > +
> > +	/*
> > +	 * Enable sensors data conversion and IRQ. We need to lock the
> > +	 * interface mutex since hwmon has just been created and the
> > +	 * corresponding sysfs files are accessible from user-space,
> > +	 * which theoretically may cause races.
> > +	 */
> 
> What if those userspace actions make a request which requires an interrupt ?

In case if CONFIG_SENSORS_BT1_PVT_ALARMS is enabled, then there is no such
action. Though user-space may set some alarm thresholds, which could cause
immediate hwmon event raise. But even if they did the event status will
be left pending and handled after we enable the IRQs in the next lines.

If CONFIG_SENSORS_BT1_PVT_ALARMS is disabled, then the IRQs are enabled/disabled
in the pvt_read_data() directly to perform the sensor conversion.

> 
> > +	mutex_lock(&pvt->iface_mtx);
> > +	pvt_update(pvt->regs + PVT_INTR_MASK, PVT_INTR_DVALID, 0);
> > +	pvt_update(pvt->regs + PVT_CTRL, PVT_CTRL_EN, PVT_CTRL_EN);
> > +	mutex_unlock(&pvt->iface_mtx);
> > +
> > +	return 0;
> > +}
> > +
> > +#else /* !CONFIG_SENSORS_BT1_PVT_ALARMS */
> > +

[nip]

> > diff --git a/drivers/hwmon/bt1-pvt.h b/drivers/hwmon/bt1-pvt.h
> > new file mode 100644
> > index 000000000000..7851ed947877
> > --- /dev/null
> > +++ b/drivers/hwmon/bt1-pvt.h
> > @@ -0,0 +1,237 @@
> > +/* SPDX-License-Identifier: GPL-2.0-only */
> > +/*
> > + * Copyright (C) 2020 BAIKAL ELECTRONICS, JSC
> > + *
> > + * Baikal-T1 Process, Voltage, Temperature sensor driver
> > + */
> > +#ifndef __HWMON_BT1_PVT_H__
> > +#define __HWMON_BT1_PVT_H__
> > +
> > +#include <linux/kernel.h>
> > +#include <linux/platform_device.h>
> > +#include <linux/io.h>
> > +#include <linux/mutex.h>
> > +#include <linux/seqlock.h>
> > +#include <linux/completion.h>
> > +#include <linux/sysfs.h>
> > +#include <linux/hwmon.h>
> 
> Alphabetic order, please, and drop unnecessary includes.

Ok.

> 
> > +

[nip]

> > +
> > +/*
> > + * struct pvt_sensor_info - Baikal-T1 PVT sensor informational structure
> > + * @label: hwmon sensor label.
> > + * @mode: PVT mode corresponding to the channel.
> > + * @thres_base: upper and lower threshold values of the sensor.
> > + * @thres_sts_lo: low threshold status bitfield.
> > + * @thres_sts_hi: high threshold status bitfield.
> > + * @sysfs_min_alarm: pointer to a min-alarm sysfs filename.
> > + * @sysfs_min_alarm: pointer to a max-alarm sysfs filename.
> > + */
> > +struct pvt_sensor_info {
> > +	const char *label;
> > +	u32 mode;
> > +	unsigned long thres_base;
> > +	u32 thres_sts_lo;
> > +	u32 thres_sts_hi;
> > +	const char *sysfs_min_alarm;
> > +	const char *sysfs_max_alarm;
> > +};
> > +
> > +#define PVT_SENSOR_INFO(_label, _file, _mode, _thres)			\
> 
> _file seems to be a global define or variable, or at least checkpatch
> complains about its use.

Hm, mine didn't complain about it. Otherwise I would have fixed it in the first
place. Though I'll remove that name from here anyway, since the
hwmon_notify_event() notifier is utilized, which requires sensor type, attribute
and channel/index. Thus explicit sysfs_min_alarm and sysfs_max_alarm names
aren't needed anymore.

-Sergey

> 
> > +	{								\
> > +		.label = _label,					\
> > +		.mode = PVT_CTRL_MODE_ ##_mode,				\
> > +		.thres_base = PVT_ ##_thres,				\
> > +		.thres_sts_lo = PVT_INTR_ ##_thres## _LO,		\
> > +		.thres_sts_hi = PVT_INTR_ ##_thres## _HI,		\
> > +		.sysfs_min_alarm = _file "_min_alarm",			\
> > +		.sysfs_max_alarm = _file "_max_alarm"			\
> > +	}
> > +

[nip]

> > +
> > +#endif /* __HWMON_BT1_PVT_H__ */