[PATCH v2] hwmon: (pmbus) Add support for MPS MP2949A

[PATCH v2] hwmon: (pmbus) Add support for MPS MP2949A

[ainux.wang]

From: "Ainux.Wang" <ainux.wang@gmail.com>

Add support for MP2949A device from Monolithic Power Systems, Inc. (MPS).
This is a triple-loop, digital, multi-phase controller.
This device:
- Supports up to three power rail.
- Provides 6 pulse-width modulations (PWMs), and can be configured up
  to 6-phase operation for Rail A , up to 2-phase operation for Rail B
  and up to 1-phase operation for Rail C.
- The PMBus registers are distributed into three pages: Page 0, Page 1,
  Page 2. Page 0 contains the registers for Rail A and most of the common
  settings for all of the rails. Page 1 contains register information for
  Rail B. Page 2 contains register information for Rail C.
- The MP2949A supports both 5mV VID step and 10mv VID step for IMVP8 and
  IMVP9 with only one DAC for each rail to generate REF.

Signed-off-by: Ainux.Wang <ainux.wang@gmail.com>
---
 Documentation/hwmon/index.rst   |   1 +
 Documentation/hwmon/mp2949a.rst |  44 ++++++++++++
 drivers/hwmon/pmbus/Kconfig     |   9 +++
 drivers/hwmon/pmbus/Makefile    |   1 +
 drivers/hwmon/pmbus/mp2949a.c   | 119 ++++++++++++++++++++++++++++++++
 5 files changed, 174 insertions(+)
 create mode 100644 Documentation/hwmon/mp2949a.rst
 create mode 100644 drivers/hwmon/pmbus/mp2949a.c

diff --git a/Documentation/hwmon/index.rst b/Documentation/hwmon/index.rst
index 9ed60fa84cbe..56aac3b1678d 100644
--- a/Documentation/hwmon/index.rst
+++ b/Documentation/hwmon/index.rst
@@ -137,6 +137,7 @@ Hardware Monitoring Kernel Drivers
    mcp3021
    menf21bmc
    mlxreg-fan
+   mp2949a
    mp2975
    nct6683
    nct6775
diff --git a/Documentation/hwmon/mp2949a.rst b/Documentation/hwmon/mp2949a.rst
new file mode 100644
index 000000000000..ac4084e067f1
--- /dev/null
+++ b/Documentation/hwmon/mp2949a.rst
@@ -0,0 +1,44 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+Kernel driver mp2949a
+====================
+
+Supported chips:
+
+  * MPS MP2949A
+
+    Prefix: 'mp2949a'
+
+Author:
+
+	Ainux Wang <ainux.wang@gmail.com>
+
+Description
+-----------
+
+This driver implements support for Monolithic Power Systems, Inc. (MPS)
+triple-loop, digital, multi-phase controller MP2949A.
+
+This device:
+
+- Supports up to three power rail.
+- Provides 6 pulse-width modulations (PWMs), and can be configured up
+  to 6-phase operation for Rail A , up to 2-phase operation for Rail B
+  and up to 1-phase operation for Rail C.
+- The PMBus registers are distributed into three pages: Page 0, Page 1,
+  Page 2. Page 0 contains the registers for Rail A and most of the common
+  settings for all of the rails. Page 1 contains register information for
+  Rail B. Page 2 contains register information for Rail C.
+- The MP2949A supports both 5mV VID step and 10mv VID step for IMVP8 and
+  IMVP9 with only one DAC for each rail to generate REF.
+
+Device supports:
+
+- SVID interface.
+- PMBus rev 1.2 interface.
+
+Device supports direct format for reading output power.
+Device supports linear format for reading input voltage and output current
+and temperature.
+Device supports VID for reading output voltage.
+The below VID modes are supported: VR12, VR13, IMVP8, IMVP9.
diff --git a/drivers/hwmon/pmbus/Kconfig b/drivers/hwmon/pmbus/Kconfig
index 37a5c39784fa..b1344b265976 100644
--- a/drivers/hwmon/pmbus/Kconfig
+++ b/drivers/hwmon/pmbus/Kconfig
@@ -248,6 +248,15 @@ config SENSORS_MAX8688
 	  This driver can also be built as a module. If so, the module will
 	  be called max8688.
 
+config SENSORS_MP2949A
+	tristate "MPS MP2949A"
+	help
+	  If you say yes here you get hardware monitoring support for MPS
+	  MP2949A Triple Loop Digital Multi-Phase Controller.
+
+	  This driver can also be built as a module. If so, the module will
+	  be called mp2949a.
+
 config SENSORS_MP2975
 	tristate "MPS MP2975"
 	help
diff --git a/drivers/hwmon/pmbus/Makefile b/drivers/hwmon/pmbus/Makefile
index f8dcc27cd56a..bfb55ab12da1 100644
--- a/drivers/hwmon/pmbus/Makefile
+++ b/drivers/hwmon/pmbus/Makefile
@@ -28,6 +28,7 @@ obj-$(CONFIG_SENSORS_MAX20751)	+= max20751.o
 obj-$(CONFIG_SENSORS_MAX31785)	+= max31785.o
 obj-$(CONFIG_SENSORS_MAX34440)	+= max34440.o
 obj-$(CONFIG_SENSORS_MAX8688)	+= max8688.o
+obj-$(CONFIG_SENSORS_MP2949A)	+= mp2949a.o
 obj-$(CONFIG_SENSORS_MP2975)	+= mp2975.o
 obj-$(CONFIG_SENSORS_PM6764TR)	+= pm6764tr.o
 obj-$(CONFIG_SENSORS_PXE1610)	+= pxe1610.o
diff --git a/drivers/hwmon/pmbus/mp2949a.c b/drivers/hwmon/pmbus/mp2949a.c
new file mode 100644
index 000000000000..d68e8526abe3
--- /dev/null
+++ b/drivers/hwmon/pmbus/mp2949a.c
@@ -0,0 +1,119 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Hardware monitoring driver for Monolithic Power Systems MP2949A
+ *
+ * Copyright (c) 2021 Lemote Technologies. All rights reserved.
+ * Copyright (c) 2021 Ainux <ainux.wang@gmail.com>
+ */
+
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include "pmbus.h"
+
+#define MP2949A_PAGE_NUM		3
+
+static int mp2949a_read_byte_data(struct i2c_client *client, int page, int reg)
+{
+	switch (reg) {
+	case PMBUS_VOUT_MODE:
+		/* This chip do not support the VOUT_MODE command. */
+		return -EINVAL;
+	default:
+		return -ENODATA;
+	}
+}
+
+static int mp2949a_identify(struct i2c_client *client,
+			    struct pmbus_driver_info *info)
+{
+	u8 vout_params;
+	int i, ret;
+
+	for (i = 0; i < MP2949A_PAGE_NUM; i++) {
+		/* Read the register with VOUT scaling value.*/
+		ret = pmbus_read_byte_data(client, i, PMBUS_VOUT_MODE);
+		if (ret < 0)
+			return ret;
+
+		/*
+		 * Rail A bit 5, Rail B bit 4, Rail C bit 3.
+		 * 1'b1: 5mV  (vr12/imvp8)
+		 * 1'b0: 10mv (imvp9)
+		 */
+		vout_params = ret & ~BIT(5-i);
+		if (vout_params)
+			info->vrm_version[i] = vr12;
+		else
+			info->vrm_version[i] = imvp9;
+
+	}
+
+	return 0;
+}
+
+static struct pmbus_driver_info mp2949a_info = {
+	.pages = MP2949A_PAGE_NUM,
+	.format[PSC_VOLTAGE_IN] = linear,
+	.format[PSC_VOLTAGE_OUT] = vid,
+	.format[PSC_CURRENT_OUT] = linear,
+	.format[PSC_TEMPERATURE] = linear,
+	.format[PSC_POWER] = direct,
+	.m[PSC_POWER] = 1,
+	.b[PSC_POWER] = 0,
+	.R[PSC_POWER] = 0,
+	.func[0] = PMBUS_HAVE_VIN | PMBUS_HAVE_VOUT | PMBUS_HAVE_STATUS_VOUT |
+		PMBUS_HAVE_IOUT | PMBUS_HAVE_STATUS_IOUT |
+		PMBUS_HAVE_TEMP | PMBUS_HAVE_POUT,
+	.func[1] = PMBUS_HAVE_VOUT | PMBUS_HAVE_STATUS_VOUT |
+		PMBUS_HAVE_IOUT | PMBUS_HAVE_STATUS_IOUT |
+		PMBUS_HAVE_POUT,
+	.func[2] = PMBUS_HAVE_VOUT | PMBUS_HAVE_STATUS_VOUT |
+		PMBUS_HAVE_IOUT | PMBUS_HAVE_STATUS_IOUT |
+		PMBUS_HAVE_POUT,
+	.identify = mp2949a_identify,
+	.read_byte_data = mp2949a_read_byte_data,
+};
+
+static int mp2949a_probe(struct i2c_client *client,
+			  const struct i2c_device_id *id)
+{
+	struct pmbus_driver_info *info;
+
+	info = devm_kmemdup(&client->dev, &mp2949a_info, sizeof(*info),
+			    GFP_KERNEL);
+	if (!info)
+		return -ENOMEM;
+
+	return pmbus_do_probe(client, info);
+}
+
+static const struct i2c_device_id mp2949a_id[] = {
+	{"mp2949a", 0},
+	{}
+};
+
+MODULE_DEVICE_TABLE(i2c, mp2949a_id);
+
+static const struct of_device_id mp2949a_of_match[] = {
+	{.compatible = "mps,mp2949a"},
+	{}
+};
+MODULE_DEVICE_TABLE(of, mp2949a_of_match);
+
+static struct i2c_driver mp2949a_driver = {
+	.driver = {
+		.name = "mp2949a",
+		.of_match_table = of_match_ptr(mp2949a_of_match),
+	},
+	.probe = mp2949a_probe,
+	.id_table = mp2949a_id,
+};
+
+module_i2c_driver(mp2949a_driver);
+
+MODULE_AUTHOR("Ainux <ainux.wang@gmail.com>");
+MODULE_DESCRIPTION("PMBus driver for Monolithic Power Systems MP2949A");
+MODULE_LICENSE("GPL");
-- 
2.18.1

Re: [PATCH v2] hwmon: (pmbus) Add support for MPS MP2949A

[Guenter Roeck]

On Fri, Jun 18, 2021 at 11:09:34AM +0800, ainux.wang@gmail.com wrote:
> From: "Ainux.Wang" <ainux.wang@gmail.com>
> 
> Add support for MP2949A device from Monolithic Power Systems, Inc. (MPS).
> This is a triple-loop, digital, multi-phase controller.
> This device:
> - Supports up to three power rail.
> - Provides 6 pulse-width modulations (PWMs), and can be configured up
>   to 6-phase operation for Rail A , up to 2-phase operation for Rail B
>   and up to 1-phase operation for Rail C.
> - The PMBus registers are distributed into three pages: Page 0, Page 1,
>   Page 2. Page 0 contains the registers for Rail A and most of the common
>   settings for all of the rails. Page 1 contains register information for
>   Rail B. Page 2 contains register information for Rail C.
> - The MP2949A supports both 5mV VID step and 10mv VID step for IMVP8 and
>   IMVP9 with only one DAC for each rail to generate REF.
> 
> Signed-off-by: Ainux.Wang <ainux.wang@gmail.com>
> ---

Change log goes here. My normal response to patches with missing change log is:

<Formletter>  
Change log goes here. If it is missing, I won't know what changed.
That means I will have to dig out older patch versions to compare.
That costs time and would hold up both this patch as well as all other
patches which I still have to review.

For this reason, I will not review patches without change log.
</Formletter>

so you are lucky that your previous version is recent enough that I remember
at least some of it. However, please do provide change logs in the future.

>  Documentation/hwmon/index.rst   |   1 +
>  Documentation/hwmon/mp2949a.rst |  44 ++++++++++++
>  drivers/hwmon/pmbus/Kconfig     |   9 +++
>  drivers/hwmon/pmbus/Makefile    |   1 +
>  drivers/hwmon/pmbus/mp2949a.c   | 119 ++++++++++++++++++++++++++++++++
>  5 files changed, 174 insertions(+)
>  create mode 100644 Documentation/hwmon/mp2949a.rst
>  create mode 100644 drivers/hwmon/pmbus/mp2949a.c
> 
> diff --git a/Documentation/hwmon/index.rst b/Documentation/hwmon/index.rst
> index 9ed60fa84cbe..56aac3b1678d 100644
> --- a/Documentation/hwmon/index.rst
> +++ b/Documentation/hwmon/index.rst
> @@ -137,6 +137,7 @@ Hardware Monitoring Kernel Drivers
>     mcp3021
>     menf21bmc
>     mlxreg-fan
> +   mp2949a
>     mp2975
>     nct6683
>     nct6775
> diff --git a/Documentation/hwmon/mp2949a.rst b/Documentation/hwmon/mp2949a.rst
> new file mode 100644
> index 000000000000..ac4084e067f1
> --- /dev/null
> +++ b/Documentation/hwmon/mp2949a.rst
> @@ -0,0 +1,44 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +
> +Kernel driver mp2949a
> +====================
> +
> +Supported chips:
> +
> +  * MPS MP2949A
> +
> +    Prefix: 'mp2949a'
> +
> +Author:
> +
> +	Ainux Wang <ainux.wang@gmail.com>
> +
> +Description
> +-----------
> +
> +This driver implements support for Monolithic Power Systems, Inc. (MPS)
> +triple-loop, digital, multi-phase controller MP2949A.
> +
> +This device:
> +
> +- Supports up to three power rail.

rails

> +- Provides 6 pulse-width modulations (PWMs), and can be configured up

can be configured for ...

> +  to 6-phase operation for Rail A , up to 2-phase operation for Rail B

Rail B,

> +  and up to 1-phase operation for Rail C.
> +- The PMBus registers are distributed into three pages: Page 0, Page 1,
> +  Page 2. Page 0 contains the registers for Rail A and most of the common
> +  settings for all of the rails. Page 1 contains register information for
> +  Rail B. Page 2 contains register information for Rail C.
> +- The MP2949A supports both 5mV VID step and 10mv VID step for IMVP8 and
> +  IMVP9 with only one DAC for each rail to generate REF.

Please explain REF.

> +
> +Device supports:
> +
> +- SVID interface.
> +- PMBus rev 1.2 interface.
> +
> +Device supports direct format for reading output power.
> +Device supports linear format for reading input voltage and output current

input voltage, output current, and temperature.

> +and temperature.
> +Device supports VID for reading output voltage.
> +The below VID modes are supported: VR12, VR13, IMVP8, IMVP9.

The following

> diff --git a/drivers/hwmon/pmbus/Kconfig b/drivers/hwmon/pmbus/Kconfig
> index 37a5c39784fa..b1344b265976 100644
> --- a/drivers/hwmon/pmbus/Kconfig
> +++ b/drivers/hwmon/pmbus/Kconfig
> @@ -248,6 +248,15 @@ config SENSORS_MAX8688
>  	  This driver can also be built as a module. If so, the module will
>  	  be called max8688.
>  
> +config SENSORS_MP2949A
> +	tristate "MPS MP2949A"
> +	help
> +	  If you say yes here you get hardware monitoring support for MPS
> +	  MP2949A Triple Loop Digital Multi-Phase Controller.
> +
> +	  This driver can also be built as a module. If so, the module will
> +	  be called mp2949a.
> +
>  config SENSORS_MP2975
>  	tristate "MPS MP2975"
>  	help
> diff --git a/drivers/hwmon/pmbus/Makefile b/drivers/hwmon/pmbus/Makefile
> index f8dcc27cd56a..bfb55ab12da1 100644
> --- a/drivers/hwmon/pmbus/Makefile
> +++ b/drivers/hwmon/pmbus/Makefile
> @@ -28,6 +28,7 @@ obj-$(CONFIG_SENSORS_MAX20751)	+= max20751.o
>  obj-$(CONFIG_SENSORS_MAX31785)	+= max31785.o
>  obj-$(CONFIG_SENSORS_MAX34440)	+= max34440.o
>  obj-$(CONFIG_SENSORS_MAX8688)	+= max8688.o
> +obj-$(CONFIG_SENSORS_MP2949A)	+= mp2949a.o
>  obj-$(CONFIG_SENSORS_MP2975)	+= mp2975.o
>  obj-$(CONFIG_SENSORS_PM6764TR)	+= pm6764tr.o
>  obj-$(CONFIG_SENSORS_PXE1610)	+= pxe1610.o
> diff --git a/drivers/hwmon/pmbus/mp2949a.c b/drivers/hwmon/pmbus/mp2949a.c
> new file mode 100644
> index 000000000000..d68e8526abe3
> --- /dev/null
> +++ b/drivers/hwmon/pmbus/mp2949a.c
> @@ -0,0 +1,119 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Hardware monitoring driver for Monolithic Power Systems MP2949A
> + *
> + * Copyright (c) 2021 Lemote Technologies. All rights reserved.
> + * Copyright (c) 2021 Ainux <ainux.wang@gmail.com>
> + */
> +
> +#include <linux/err.h>
> +#include <linux/i2c.h>
> +#include <linux/init.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include "pmbus.h"
> +
> +#define MP2949A_PAGE_NUM		3
> +
> +static int mp2949a_read_byte_data(struct i2c_client *client, int page, int reg)
> +{
> +	switch (reg) {
> +	case PMBUS_VOUT_MODE:
> +		/* This chip do not support the VOUT_MODE command. */

s/do/does/

This warrants a more detailed explanation: What happens if the command
is sent to the chip, and why is it not possible to rely on the standard
response to unsupported commands ? 

> +		return -EINVAL;
> +	default:
> +		return -ENODATA;
> +	}
> +}
> +
> +static int mp2949a_identify(struct i2c_client *client,
> +			    struct pmbus_driver_info *info)
> +{
> +	u8 vout_params;
> +	int i, ret;
> +
> +	for (i = 0; i < MP2949A_PAGE_NUM; i++) {
> +		/* Read the register with VOUT scaling value.*/
> +		ret = pmbus_read_byte_data(client, i, PMBUS_VOUT_MODE);
                                                      ^^^^^^^^^^^^^^^
Should this be MFR_VR_CONFIG ?

> +		if (ret < 0)
> +			return ret;
> +
> +		/*
> +		 * Rail A bit 5, Rail B bit 4, Rail C bit 3.
> +		 * 1'b1: 5mV  (vr12/imvp8)
> +		 * 1'b0: 10mv (imvp9)
> +		 */
> +		vout_params = ret & ~BIT(5-i);

space before and after '-'. vout_params is really unnecessary; just do
the check directly in the if() statement.

> +		if (vout_params)
> +			info->vrm_version[i] = vr12;
> +		else
> +			info->vrm_version[i] = imvp9;
> +

Unnecessary empty line.

checkpatch --strict reports this and the above problem, plus another
alignment problem. Please fix everything it reports.

> +	}
> +
> +	return 0;
> +}
> +
> +static struct pmbus_driver_info mp2949a_info = {
> +	.pages = MP2949A_PAGE_NUM,
> +	.format[PSC_VOLTAGE_IN] = linear,
> +	.format[PSC_VOLTAGE_OUT] = vid,
> +	.format[PSC_CURRENT_OUT] = linear,
> +	.format[PSC_TEMPERATURE] = linear,
> +	.format[PSC_POWER] = direct,
> +	.m[PSC_POWER] = 1,
> +	.b[PSC_POWER] = 0,
> +	.R[PSC_POWER] = 0,
> +	.func[0] = PMBUS_HAVE_VIN | PMBUS_HAVE_VOUT | PMBUS_HAVE_STATUS_VOUT |
> +		PMBUS_HAVE_IOUT | PMBUS_HAVE_STATUS_IOUT |
> +		PMBUS_HAVE_TEMP | PMBUS_HAVE_POUT,
> +	.func[1] = PMBUS_HAVE_VOUT | PMBUS_HAVE_STATUS_VOUT |
> +		PMBUS_HAVE_IOUT | PMBUS_HAVE_STATUS_IOUT |
> +		PMBUS_HAVE_POUT,
> +	.func[2] = PMBUS_HAVE_VOUT | PMBUS_HAVE_STATUS_VOUT |
> +		PMBUS_HAVE_IOUT | PMBUS_HAVE_STATUS_IOUT |
> +		PMBUS_HAVE_POUT,
> +	.identify = mp2949a_identify,
> +	.read_byte_data = mp2949a_read_byte_data,
> +};
> +
> +static int mp2949a_probe(struct i2c_client *client,
> +			  const struct i2c_device_id *id)
> +{
> +	struct pmbus_driver_info *info;
> +
> +	info = devm_kmemdup(&client->dev, &mp2949a_info, sizeof(*info),
> +			    GFP_KERNEL);
> +	if (!info)
> +		return -ENOMEM;
> +
> +	return pmbus_do_probe(client, info);
> +}
> +
> +static const struct i2c_device_id mp2949a_id[] = {
> +	{"mp2949a", 0},
> +	{}
> +};
> +
> +MODULE_DEVICE_TABLE(i2c, mp2949a_id);
> +
> +static const struct of_device_id mp2949a_of_match[] = {
> +	{.compatible = "mps,mp2949a"},
> +	{}
> +};
> +MODULE_DEVICE_TABLE(of, mp2949a_of_match);
> +
> +static struct i2c_driver mp2949a_driver = {
> +	.driver = {
> +		.name = "mp2949a",
> +		.of_match_table = of_match_ptr(mp2949a_of_match),
> +	},
> +	.probe = mp2949a_probe,
> +	.id_table = mp2949a_id,
> +};
> +
> +module_i2c_driver(mp2949a_driver);
> +
> +MODULE_AUTHOR("Ainux <ainux.wang@gmail.com>");
> +MODULE_DESCRIPTION("PMBus driver for Monolithic Power Systems MP2949A");
> +MODULE_LICENSE("GPL");
> -- 
> 2.18.1
> 

Re: [PATCH v2] hwmon: (pmbus) Add support for MPS MP2949A

[Ainux Wang]

Hi，Guenter
    Thanks for the review. It all sounds reasonable. I'll address it all in v3.
Best regards,
Ainux Wang.


On Sat, 19 Jun 2021 at 03:39, Guenter Roeck <linux@roeck-us.net> wrote:
>
> On Fri, Jun 18, 2021 at 11:09:34AM +0800, ainux.wang@gmail.com wrote:
> > From: "Ainux.Wang" <ainux.wang@gmail.com>
> >
> > Add support for MP2949A device from Monolithic Power Systems, Inc. (MPS).
> > This is a triple-loop, digital, multi-phase controller.
> > This device:
> > - Supports up to three power rail.
> > - Provides 6 pulse-width modulations (PWMs), and can be configured up
> >   to 6-phase operation for Rail A , up to 2-phase operation for Rail B
> >   and up to 1-phase operation for Rail C.
> > - The PMBus registers are distributed into three pages: Page 0, Page 1,
> >   Page 2. Page 0 contains the registers for Rail A and most of the common
> >   settings for all of the rails. Page 1 contains register information for
> >   Rail B. Page 2 contains register information for Rail C.
> > - The MP2949A supports both 5mV VID step and 10mv VID step for IMVP8 and
> >   IMVP9 with only one DAC for each rail to generate REF.
> >
> > Signed-off-by: Ainux.Wang <ainux.wang@gmail.com>
> > ---
>
> Change log goes here. My normal response to patches with missing change log is:
>
> <Formletter>
> Change log goes here. If it is missing, I won't know what changed.
> That means I will have to dig out older patch versions to compare.
> That costs time and would hold up both this patch as well as all other
> patches which I still have to review.
>
> For this reason, I will not review patches without change log.
> </Formletter>
>
> so you are lucky that your previous version is recent enough that I remember
> at least some of it. However, please do provide change logs in the future.
>
> >  Documentation/hwmon/index.rst   |   1 +
> >  Documentation/hwmon/mp2949a.rst |  44 ++++++++++++
> >  drivers/hwmon/pmbus/Kconfig     |   9 +++
> >  drivers/hwmon/pmbus/Makefile    |   1 +
> >  drivers/hwmon/pmbus/mp2949a.c   | 119 ++++++++++++++++++++++++++++++++
> >  5 files changed, 174 insertions(+)
> >  create mode 100644 Documentation/hwmon/mp2949a.rst
> >  create mode 100644 drivers/hwmon/pmbus/mp2949a.c
> >
> > diff --git a/Documentation/hwmon/index.rst b/Documentation/hwmon/index.rst
> > index 9ed60fa84cbe..56aac3b1678d 100644
> > --- a/Documentation/hwmon/index.rst
> > +++ b/Documentation/hwmon/index.rst
> > @@ -137,6 +137,7 @@ Hardware Monitoring Kernel Drivers
> >     mcp3021
> >     menf21bmc
> >     mlxreg-fan
> > +   mp2949a
> >     mp2975
> >     nct6683
> >     nct6775
> > diff --git a/Documentation/hwmon/mp2949a.rst b/Documentation/hwmon/mp2949a.rst
> > new file mode 100644
> > index 000000000000..ac4084e067f1
> > --- /dev/null
> > +++ b/Documentation/hwmon/mp2949a.rst
> > @@ -0,0 +1,44 @@
> > +.. SPDX-License-Identifier: GPL-2.0
> > +
> > +Kernel driver mp2949a
> > +====================
> > +
> > +Supported chips:
> > +
> > +  * MPS MP2949A
> > +
> > +    Prefix: 'mp2949a'
> > +
> > +Author:
> > +
> > +     Ainux Wang <ainux.wang@gmail.com>
> > +
> > +Description
> > +-----------
> > +
> > +This driver implements support for Monolithic Power Systems, Inc. (MPS)
> > +triple-loop, digital, multi-phase controller MP2949A.
> > +
> > +This device:
> > +
> > +- Supports up to three power rail.
>
> rails
>
> > +- Provides 6 pulse-width modulations (PWMs), and can be configured up
>
> can be configured for ...
>
> > +  to 6-phase operation for Rail A , up to 2-phase operation for Rail B
>
> Rail B,
>
> > +  and up to 1-phase operation for Rail C.
> > +- The PMBus registers are distributed into three pages: Page 0, Page 1,
> > +  Page 2. Page 0 contains the registers for Rail A and most of the common
> > +  settings for all of the rails. Page 1 contains register information for
> > +  Rail B. Page 2 contains register information for Rail C.
> > +- The MP2949A supports both 5mV VID step and 10mv VID step for IMVP8 and
> > +  IMVP9 with only one DAC for each rail to generate REF.
>
> Please explain REF.
>
> > +
> > +Device supports:
> > +
> > +- SVID interface.
> > +- PMBus rev 1.2 interface.
> > +
> > +Device supports direct format for reading output power.
> > +Device supports linear format for reading input voltage and output current
>
> input voltage, output current, and temperature.
>
> > +and temperature.
> > +Device supports VID for reading output voltage.
> > +The below VID modes are supported: VR12, VR13, IMVP8, IMVP9.
>
> The following
>
> > diff --git a/drivers/hwmon/pmbus/Kconfig b/drivers/hwmon/pmbus/Kconfig
> > index 37a5c39784fa..b1344b265976 100644
> > --- a/drivers/hwmon/pmbus/Kconfig
> > +++ b/drivers/hwmon/pmbus/Kconfig
> > @@ -248,6 +248,15 @@ config SENSORS_MAX8688
> >         This driver can also be built as a module. If so, the module will
> >         be called max8688.
> >
> > +config SENSORS_MP2949A
> > +     tristate "MPS MP2949A"
> > +     help
> > +       If you say yes here you get hardware monitoring support for MPS
> > +       MP2949A Triple Loop Digital Multi-Phase Controller.
> > +
> > +       This driver can also be built as a module. If so, the module will
> > +       be called mp2949a.
> > +
> >  config SENSORS_MP2975
> >       tristate "MPS MP2975"
> >       help
> > diff --git a/drivers/hwmon/pmbus/Makefile b/drivers/hwmon/pmbus/Makefile
> > index f8dcc27cd56a..bfb55ab12da1 100644
> > --- a/drivers/hwmon/pmbus/Makefile
> > +++ b/drivers/hwmon/pmbus/Makefile
> > @@ -28,6 +28,7 @@ obj-$(CONFIG_SENSORS_MAX20751)      += max20751.o
> >  obj-$(CONFIG_SENSORS_MAX31785)       += max31785.o
> >  obj-$(CONFIG_SENSORS_MAX34440)       += max34440.o
> >  obj-$(CONFIG_SENSORS_MAX8688)        += max8688.o
> > +obj-$(CONFIG_SENSORS_MP2949A)        += mp2949a.o
> >  obj-$(CONFIG_SENSORS_MP2975) += mp2975.o
> >  obj-$(CONFIG_SENSORS_PM6764TR)       += pm6764tr.o
> >  obj-$(CONFIG_SENSORS_PXE1610)        += pxe1610.o
> > diff --git a/drivers/hwmon/pmbus/mp2949a.c b/drivers/hwmon/pmbus/mp2949a.c
> > new file mode 100644
> > index 000000000000..d68e8526abe3
> > --- /dev/null
> > +++ b/drivers/hwmon/pmbus/mp2949a.c
> > @@ -0,0 +1,119 @@
> > +// SPDX-License-Identifier: GPL-2.0-or-later
> > +/*
> > + * Hardware monitoring driver for Monolithic Power Systems MP2949A
> > + *
> > + * Copyright (c) 2021 Lemote Technologies. All rights reserved.
> > + * Copyright (c) 2021 Ainux <ainux.wang@gmail.com>
> > + */
> > +
> > +#include <linux/err.h>
> > +#include <linux/i2c.h>
> > +#include <linux/init.h>
> > +#include <linux/kernel.h>
> > +#include <linux/module.h>
> > +#include "pmbus.h"
> > +
> > +#define MP2949A_PAGE_NUM             3
> > +
> > +static int mp2949a_read_byte_data(struct i2c_client *client, int page, int reg)
> > +{
> > +     switch (reg) {
> > +     case PMBUS_VOUT_MODE:
> > +             /* This chip do not support the VOUT_MODE command. */
>
> s/do/does/
>
> This warrants a more detailed explanation: What happens if the command
> is sent to the chip, and why is it not possible to rely on the standard
> response to unsupported commands ?
>
> > +             return -EINVAL;
> > +     default:
> > +             return -ENODATA;
> > +     }
> > +}
> > +
> > +static int mp2949a_identify(struct i2c_client *client,
> > +                         struct pmbus_driver_info *info)
> > +{
> > +     u8 vout_params;
> > +     int i, ret;
> > +
> > +     for (i = 0; i < MP2949A_PAGE_NUM; i++) {
> > +             /* Read the register with VOUT scaling value.*/
> > +             ret = pmbus_read_byte_data(client, i, PMBUS_VOUT_MODE);
>                                                       ^^^^^^^^^^^^^^^
> Should this be MFR_VR_CONFIG ?
>
> > +             if (ret < 0)
> > +                     return ret;
> > +
> > +             /*
> > +              * Rail A bit 5, Rail B bit 4, Rail C bit 3.
> > +              * 1'b1: 5mV  (vr12/imvp8)
> > +              * 1'b0: 10mv (imvp9)
> > +              */
> > +             vout_params = ret & ~BIT(5-i);
>
> space before and after '-'. vout_params is really unnecessary; just do
> the check directly in the if() statement.
>
> > +             if (vout_params)
> > +                     info->vrm_version[i] = vr12;
> > +             else
> > +                     info->vrm_version[i] = imvp9;
> > +
>
> Unnecessary empty line.
>
> checkpatch --strict reports this and the above problem, plus another
> alignment problem. Please fix everything it reports.
>
> > +     }
> > +
> > +     return 0;
> > +}
> > +
> > +static struct pmbus_driver_info mp2949a_info = {
> > +     .pages = MP2949A_PAGE_NUM,
> > +     .format[PSC_VOLTAGE_IN] = linear,
> > +     .format[PSC_VOLTAGE_OUT] = vid,
> > +     .format[PSC_CURRENT_OUT] = linear,
> > +     .format[PSC_TEMPERATURE] = linear,
> > +     .format[PSC_POWER] = direct,
> > +     .m[PSC_POWER] = 1,
> > +     .b[PSC_POWER] = 0,
> > +     .R[PSC_POWER] = 0,
> > +     .func[0] = PMBUS_HAVE_VIN | PMBUS_HAVE_VOUT | PMBUS_HAVE_STATUS_VOUT |
> > +             PMBUS_HAVE_IOUT | PMBUS_HAVE_STATUS_IOUT |
> > +             PMBUS_HAVE_TEMP | PMBUS_HAVE_POUT,
> > +     .func[1] = PMBUS_HAVE_VOUT | PMBUS_HAVE_STATUS_VOUT |
> > +             PMBUS_HAVE_IOUT | PMBUS_HAVE_STATUS_IOUT |
> > +             PMBUS_HAVE_POUT,
> > +     .func[2] = PMBUS_HAVE_VOUT | PMBUS_HAVE_STATUS_VOUT |
> > +             PMBUS_HAVE_IOUT | PMBUS_HAVE_STATUS_IOUT |
> > +             PMBUS_HAVE_POUT,
> > +     .identify = mp2949a_identify,
> > +     .read_byte_data = mp2949a_read_byte_data,
> > +};
> > +
> > +static int mp2949a_probe(struct i2c_client *client,
> > +                       const struct i2c_device_id *id)
> > +{
> > +     struct pmbus_driver_info *info;
> > +
> > +     info = devm_kmemdup(&client->dev, &mp2949a_info, sizeof(*info),
> > +                         GFP_KERNEL);
> > +     if (!info)
> > +             return -ENOMEM;
> > +
> > +     return pmbus_do_probe(client, info);
> > +}
> > +
> > +static const struct i2c_device_id mp2949a_id[] = {
> > +     {"mp2949a", 0},
> > +     {}
> > +};
> > +
> > +MODULE_DEVICE_TABLE(i2c, mp2949a_id);
> > +
> > +static const struct of_device_id mp2949a_of_match[] = {
> > +     {.compatible = "mps,mp2949a"},
> > +     {}
> > +};
> > +MODULE_DEVICE_TABLE(of, mp2949a_of_match);
> > +
> > +static struct i2c_driver mp2949a_driver = {
> > +     .driver = {
> > +             .name = "mp2949a",
> > +             .of_match_table = of_match_ptr(mp2949a_of_match),
> > +     },
> > +     .probe = mp2949a_probe,
> > +     .id_table = mp2949a_id,
> > +};
> > +
> > +module_i2c_driver(mp2949a_driver);
> > +
> > +MODULE_AUTHOR("Ainux <ainux.wang@gmail.com>");
> > +MODULE_DESCRIPTION("PMBus driver for Monolithic Power Systems MP2949A");
> > +MODULE_LICENSE("GPL");
> > --
> > 2.18.1
> >