[PATCH v3 0/2] hwmon: (adt7475) Added attenuator bypass support

[PATCH v3 0/2] hwmon: (adt7475) Added attenuator bypass support

[Logan Shaw]

The ADT7473 and ADT7475 support bypassing voltage input attenuators on
voltage input 1 and the ADT7476 and ADT7490 additionally support
bypassing voltage input attenuators on voltage inputs 0, 3, and 4. This
can be useful to improve measurement resolution when measuring voltages
0 V - 2.25 V.

This patch adds 4 optional devicetree properties to the adt7475
driver, each setting the attenuator bypass (or clearing) on a
specific voltage input.

* v3
- removed the functionality to set the global attenuator bypass.
- added functionality to allow bypassing voltage input 1 on the
	ADT7473 and ADT7475.
- added DTS definition file adt7475.yaml and 4 new properties.
- added the previousely missing newline character to the end of
  	file adt7475.c. 

* v2
- removed sysfs changes from patch
- removed adt7475_write macro from patch and replaced it by using
	the i2c_smbus_write_byte_data function directly in code.
- removed config4_attenuate_index function from patch and replaced it
	by modifying the function  load_individual_bypass_attenuators
	to use hard coded bit values.
- modified function load_individual_bypass_attenuators to use 4 if
	statements, one for each voltage input, replacing the for loop.
- modified function adt7475_probe to check the device is a ADT7476 or
	ADT7490 (other devices do not support bypassing all or
	individual attenuators), and only then set the relevant bits.
- added new file adt7475.txt to document the new devicetree properties.
- removed c++ style comments. 

Logan Shaw (2):
  hwmon: (adt7475) Added attenuator bypass support
  hwmon: (adt7475) Added attenuator bypass support

 .../devicetree/bindings/hwmon/adt7475.yaml    | 90 +++++++++++++++++++
 drivers/hwmon/adt7475.c                       | 76 ++++++++++++++++
 2 files changed, 166 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/hwmon/adt7475.yaml

-- 
2.25.0

[PATCH v3 1/2] hwmon: (adt7475) Added attenuator bypass support

[Logan Shaw]

Added support for reading DTS properties to set attenuators on
device probe for the ADT7473, ADT7475, ADT7476, and ADT7490.

Signed-off-by: Logan Shaw <logan.shaw@alliedtelesis.co.nz>
---
---
 drivers/hwmon/adt7475.c | 76 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 76 insertions(+)

diff --git a/drivers/hwmon/adt7475.c b/drivers/hwmon/adt7475.c
index 6c64d50c9aae..2bb787acb363 100644
--- a/drivers/hwmon/adt7475.c
+++ b/drivers/hwmon/adt7475.c
@@ -19,6 +19,7 @@
 #include <linux/hwmon-vid.h>
 #include <linux/err.h>
 #include <linux/jiffies.h>
+#include <linux/of.h>
 #include <linux/util_macros.h>
 
 /* Indexes for the sysfs hooks */
@@ -1457,6 +1458,76 @@ static int adt7475_update_limits(struct i2c_client *client)
 	return 0;
 }
 
+/**
+ * Attempts to read a u32 property from the DTS, if there is no error and
+ * the properties value is zero then the bit given by parameter bit_index
+ * is cleared in the parameter config. If the value is non-zero then the bit
+ * is set.
+ * 
+ * If reading the dts property returned an error code then it is returned and
+ * the config parameter is not modified.
+ */
+static int modify_config_from_dts_prop(const struct i2c_client *client,
+								char *dts_property, u8 *config, u8 bit_index) {
+	u32 is_attenuator_bypassed = 0;
+	int ret = of_property_read_u32(client->dev.of_node, dts_property,
+									&is_attenuator_bypassed);
+
+	if (! ret) {
+			if (is_attenuator_bypassed)
+		*config |= (1 << bit_index);
+	else
+		*config &= ~(1 << bit_index);
+	}
+
+	return ret;
+}
+
+/**
+ * Reads all individual voltage input bypass attenuator properties from the
+ * DTS, and if the property is present the corresponding bit is set in the
+ * register.
+
+ * Properties are in the form of "bypass-attenuator-inx", where x is an
+ * integer from the set {0, 1, 3, 4} (can not bypass in2 attenuator).
+.* 
+ * The adt7473 and adt7475 only support bypassing in1.
+ * 
+ * Returns a negative error code if there was an error writing to the register.
+ */
+static int load_all_bypass_attenuators(const struct i2c_client *client, 
+					      int chip, u8 *config2, u8 *config4)
+{
+	u8 config2_copy = *config2;
+	u8 config4_copy = *config4;
+
+	if (chip == adt7476 || chip == adt7490) {
+		modify_config_from_dts_prop(client, "bypass-attenuator-in0",
+									&config4_copy, 4);
+		modify_config_from_dts_prop(client, "bypass-attenuator-in1",
+									&config4_copy, 5);
+		modify_config_from_dts_prop(client, "bypass-attenuator-in3",
+									&config4_copy, 6);
+		modify_config_from_dts_prop(client, "bypass-attenuator-in4",
+									&config4_copy, 7);
+
+		if (i2c_smbus_write_byte_data(client, REG_CONFIG4, config4_copy) < 0)
+			return -EREMOTEIO;
+
+		*config4 = config4_copy;
+	} else if (chip == adt7473 || chip == adt7475) {
+		modify_config_from_dts_prop(client, "bypass-attenuator-in1",
+									&config2_copy, 5);
+
+		if (i2c_smbus_write_byte_data(client, REG_CONFIG2, config2_copy) < 0)
+			return -EREMOTEIO;
+
+		*config2 = config2_copy;
+	}
+
+	return 0;
+}
+
 static int adt7475_probe(struct i2c_client *client,
 			 const struct i2c_device_id *id)
 {
@@ -1546,6 +1617,11 @@ static int adt7475_probe(struct i2c_client *client,
 
 	/* Voltage attenuators can be bypassed, globally or individually */
 	config2 = adt7475_read(REG_CONFIG2);
+	if (load_all_bypass_attenuators(client, chip,
+						&config2, &(data->config4)) < 0)
+		dev_warn(&client->dev,
+			 "Error setting bypass attenuator bits\n");
+
 	if (config2 & CONFIG2_ATTN) {
 		data->bypass_attn = (0x3 << 3) | 0x3;
 	} else {
-- 
2.25.0

[PATCH v3 2/2] hwmon: (adt7475) Added attenuator bypass support

[Logan Shaw]

Added a new file documenting the adt7475 devicetree and added the four
new properties to it.

Signed-off-by: Logan Shaw <logan.shaw@alliedtelesis.co.nz>
---
---
 .../devicetree/bindings/hwmon/adt7475.yaml    | 90 +++++++++++++++++++
 1 file changed, 90 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/hwmon/adt7475.yaml

diff --git a/Documentation/devicetree/bindings/hwmon/adt7475.yaml b/Documentation/devicetree/bindings/hwmon/adt7475.yaml
new file mode 100644
index 000000000000..e201948beb35
--- /dev/null
+++ b/Documentation/devicetree/bindings/hwmon/adt7475.yaml
@@ -0,0 +1,90 @@
+# SPDX-License-Identifier: GPL-2.0
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/adt7475.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: ADT7475 hwmon sensor
+
+maintainers:
+  - Jean Delvare <jdelvare@suse.com>
+
+description: |
+  The ADT7473, ADT7475, ADT7476, and ADT7490 are thermal monitors and multiple
+  PWN fan controllers.
+
+  They support monitoring and controlling up to four fans (the ADT7490 can only
+  control up to three). They support reading a single on chip temperature
+  sensor and two off chip temperature sensors (the ADT7490 additionally
+  supports measuring up to three current external temperature sensors with
+  series resistance cancellation (SRC)).
+
+  Datasheets:
+  https://www.onsemi.com/pub/Collateral/ADT7473-D.PDF
+  https://www.onsemi.com/pub/Collateral/ADT7475-D.PDF
+  https://www.onsemi.com/pub/Collateral/ADT7476-D.PDF
+  https://www.onsemi.com/pub/Collateral/ADT7490-D.PDF
+
+  Description taken from omsemiconductors specification sheets, with minor
+  rephrasing.
+
+properties:
+  compatible:
+    enum:
+      - adi,adt7473
+      - adi,adt7475
+      - adi,adt7476
+      - adi,adt7490
+
+  reg:
+    maxItems: 1
+
+  bypass-attenuator-in0:
+    description: |
+      Configures bypassing the individual voltage input
+      attenuator, on in0. This is supported on the ADT7476 and ADT7490.
+      If set to a non-zero integer the attenuator is bypassed, if set to
+      zero the attenuator is not bypassed. If the property is absent then
+      the config register is not modified.
+    maxItems: 1
+
+  bypass-attenuator-in1:
+    description: |
+      Configures bypassing the individual voltage input
+      attenuator, on in1. This is supported on the ADT7473, ADT7475,
+      ADT7476 and ADT7490. If set to a non-zero integer the attenuator
+      is bypassed, if set to zero the attenuator is not bypassed. If the
+      property is absent then the config register is not modified.
+    maxItems: 1
+
+  bypass-attenuator-in3:
+    description: |
+      Configures bypassing the individual voltage input
+      attenuator, on in3. This is supported on the ADT7476 and ADT7490.
+      If set to a non-zero integer the attenuator is bypassed, if set to
+      zero the attenuator is not bypassed. If the property is absent then
+      the config register is not modified.
+    maxItems: 1
+
+  bypass-attenuator-in4:
+    description: |
+      Configures bypassing the individual voltage input
+      attenuator, on in4. This is supported on the ADT7476 and ADT7490.
+      If set to a non-zero integer the attenuator is bypassed, if set to
+      zero the attenuator is not bypassed. If the property is absent then
+      the config register is not modified.
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+
+examples:
+  - |
+    hwmon@2e {
+      compatible = "adi,adt7476";
+      reg = <0x2e>;
+      bypass-attenuator-in1 = <1>;
+      bypass-attenuator-in1 = <0>;
+    };
+...
-- 
2.25.0

Re: [PATCH v3 2/2] hwmon: (adt7475) Added attenuator bypass support

[Rob Herring]

On Fri, 17 Jan 2020 16:50:18 +1300, Logan Shaw wrote:
> 
> Added a new file documenting the adt7475 devicetree and added the four
> new properties to it.
> 
> Signed-off-by: Logan Shaw <logan.shaw@alliedtelesis.co.nz>
> ---
> ---
>  .../devicetree/bindings/hwmon/adt7475.yaml    | 90 +++++++++++++++++++
>  1 file changed, 90 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/hwmon/adt7475.yaml
> 

My bot found errors running 'make dt_binding_check' on your patch:

Documentation/devicetree/bindings/display/simple-framebuffer.example.dts:21.16-37.11: Warning (chosen_node_is_root): /example-0/chosen: chosen node must be at root node
Documentation/devicetree/bindings/hwmon/adt7475.example.dts:20.11-39: ERROR (duplicate_property_names): /example-0/hwmon@2e:bypass-attenuator-in1: Duplicate property name
ERROR: Input tree has errors, aborting (use -f to force output)
scripts/Makefile.lib:300: recipe for target 'Documentation/devicetree/bindings/hwmon/adt7475.example.dt.yaml' failed
make[1]: *** [Documentation/devicetree/bindings/hwmon/adt7475.example.dt.yaml] Error 2
Makefile:1263: recipe for target 'dt_binding_check' failed
make: *** [dt_binding_check] Error 2

See https://patchwork.ozlabs.org/patch/1224608
Please check and re-submit.