[PATCH v3 0/2] hwmon: pmbus: max20730: adjust the vout base on

[PATCH v3 0/2] hwmon: pmbus: max20730: adjust the vout base on

[Chu Lin]

The patchset includes:
Patch #1 - Implmentation of adjusting vout base on voltage divider
Patch #2 - device tree binding documentation

ChangeLog v1 -> v2
  - Don't do anything to the ret if an error is returned from pmbus_read_word
  - avoid overflow when doing multiplication

ChangeLog v2 -> v3
  - Provide the binding documentation in yaml format

Chu Lin (2):
  dt-bindings: hwmon: max20730: adding device tree doc for max20730
  hwmon: pmbus: max20730: adjust the vout reading given voltage divider

 .../bindings/hwmon/maxim,max20730.yaml        | 63 +++++++++++++++++++
 drivers/hwmon/pmbus/max20730.c                | 18 ++++++
 2 files changed, 81 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/hwmon/maxim,max20730.yaml

-- 
2.28.0.681.g6f77f65b4e-goog

[PATCH v3 1/2] dt-bindings: hwmon: max20730: adding device tree doc for max20730

[Chu Lin]

max20730 Integrated, Step-Down Switching Regulator with PMBus

Signed-off-by: Chu Lin <linchuyuan@google.com>
---
 .../bindings/hwmon/maxim,max20730.yaml        | 63 +++++++++++++++++++
 1 file changed, 63 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/hwmon/maxim,max20730.yaml

diff --git a/Documentation/devicetree/bindings/hwmon/maxim,max20730.yaml b/Documentation/devicetree/bindings/hwmon/maxim,max20730.yaml
new file mode 100644
index 000000000000..7372b27334c3
--- /dev/null
+++ b/Documentation/devicetree/bindings/hwmon/maxim,max20730.yaml
@@ -0,0 +1,63 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+
+$id: http://devicetree.org/schemas/hwmon/maxim,max20730.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Maxim max20730
+
+maintainers:
+  - Jean Delvare <jdelvare@suse.com>
+  - Guenter Roeck <linux@roeck-us.net>
+
+description: |
+  The MAX20730 is a fully integrated, highly efficient switching regulator
+  with PMBus for applications operating from 4.5V to 16V and requiring
+  up to 25A (max) load. This single-chip regulator provides extremely
+  compact, highefficiency power-delivery solutions with high-precision
+  output voltages and excellent transient response
+
+  Datasheets:
+    https://datasheets.maximintegrated.com/en/ds/MAX20730.pdf
+    https://datasheets.maximintegrated.com/en/ds/MAX20734.pdf
+    https://datasheets.maximintegrated.com/en/ds/MAX20743.pdf
+
+properties:
+  compatible:
+    enum:
+      - maxim,max20730
+      - maxim,max20734
+      - maxim,max20743
+
+  reg:
+    maxItems: 1
+
+  vout-voltage-divider:
+    description: |
+      If voltage divider presents at vout, the voltage at voltage sensor pin
+      will be scaled. The properties will convert the raw reading to a more
+      meaningful number if voltage divider presents. It has two numbers,
+      the first number is the output resistor, the second number is the total
+      resistance. Therefore, the adjusted vout is equal to
+      Vout = Vout * output_resistance / total resistance.
+    $ref: /schemas/types.yaml#/definitions/uint32-array
+    minItems: 2
+    maxItems: 2
+
+required:
+  - compatible
+  - reg
+
+examples:
+  - |
+    i2c {
+      #address-cells = <1>;
+      #size-cells = <0>;
+
+      max20730@10 {
+        compatible = "maxim,max20730";
+        reg = <0x10>;
+        vout-voltage-divider = <1000 2000>; // vout would be scaled to 0.5
+      };
+    };
-- 
2.28.0.681.g6f77f65b4e-goog

[PATCH v3 2/2] hwmon: pmbus: max20730: adjust the vout reading given voltage divider

[Chu Lin]

Problem:
We use voltage dividers so that the voltage presented at the voltage
sense pins is confusing. We might need to convert these readings to more
meaningful readings given the voltage divider.

Solution:
Read the voltage divider resistance from dts and convert the voltage
reading to a more meaningful reading.

Testing:
max20730 with voltage divider

Signed-off-by: Chu Lin <linchuyuan@google.com>
---
 drivers/hwmon/pmbus/max20730.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/drivers/hwmon/pmbus/max20730.c b/drivers/hwmon/pmbus/max20730.c
index a151a2b588a5..fbf2f1e6c969 100644
--- a/drivers/hwmon/pmbus/max20730.c
+++ b/drivers/hwmon/pmbus/max20730.c
@@ -31,6 +31,7 @@ struct max20730_data {
 	struct pmbus_driver_info info;
 	struct mutex lock;	/* Used to protect against parallel writes */
 	u16 mfr_devset1;
+	u32 vout_voltage_divider[2];
 };
 
 #define to_max20730_data(x)  container_of(x, struct max20730_data, info)
@@ -114,6 +115,14 @@ static int max20730_read_word_data(struct i2c_client *client, int page,
 		max_c = max_current[data->id][(data->mfr_devset1 >> 5) & 0x3];
 		ret = val_to_direct(max_c, PSC_CURRENT_OUT, info);
 		break;
+	case PMBUS_READ_VOUT:
+		ret = pmbus_read_word_data(client, page, phase, reg);
+		if (ret > 0 && data->vout_voltage_divider[0] && data->vout_voltage_divider[1]) {
+			u64 temp = DIV_ROUND_CLOSEST_ULL((u64)ret * data->vout_voltage_divider[1],
+							 data->vout_voltage_divider[0]);
+			ret = clamp_val(temp, 0, 0xffff);
+		}
+		break;
 	default:
 		ret = -ENODATA;
 		break;
@@ -364,6 +373,15 @@ static int max20730_probe(struct i2c_client *client,
 	data->id = chip_id;
 	mutex_init(&data->lock);
 	memcpy(&data->info, &max20730_info[chip_id], sizeof(data->info));
+	if (of_property_read_u32_array(client->dev.of_node, "vout-voltage-divider",
+				       data->vout_voltage_divider,
+				       ARRAY_SIZE(data->vout_voltage_divider)) != 0)
+		memset(data->vout_voltage_divider, 0, sizeof(data->vout_voltage_divider));
+	if (data->vout_voltage_divider[1] < data->vout_voltage_divider[0]) {
+		dev_err(dev,
+			"The total resistance of voltage divider is less than output resistance\n");
+		return -ENODEV;
+	}
 
 	ret = i2c_smbus_read_word_data(client, MAX20730_MFR_DEVSET1);
 	if (ret < 0)
-- 
2.28.0.681.g6f77f65b4e-goog

Re: [PATCH v3 1/2] dt-bindings: hwmon: max20730: adding device tree doc for max20730

[Rob Herring]

On Thu, Sep 24, 2020 at 09:54:43PM +0000, Chu Lin wrote:
> max20730 Integrated, Step-Down Switching Regulator with PMBus
> 
> Signed-off-by: Chu Lin <linchuyuan@google.com>
> ---
>  .../bindings/hwmon/maxim,max20730.yaml        | 63 +++++++++++++++++++
>  1 file changed, 63 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/hwmon/maxim,max20730.yaml
> 
> diff --git a/Documentation/devicetree/bindings/hwmon/maxim,max20730.yaml b/Documentation/devicetree/bindings/hwmon/maxim,max20730.yaml
> new file mode 100644
> index 000000000000..7372b27334c3
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/hwmon/maxim,max20730.yaml
> @@ -0,0 +1,63 @@
> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +
> +$id: http://devicetree.org/schemas/hwmon/maxim,max20730.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Maxim max20730
> +
> +maintainers:
> +  - Jean Delvare <jdelvare@suse.com>
> +  - Guenter Roeck <linux@roeck-us.net>
> +
> +description: |
> +  The MAX20730 is a fully integrated, highly efficient switching regulator
> +  with PMBus for applications operating from 4.5V to 16V and requiring
> +  up to 25A (max) load. This single-chip regulator provides extremely
> +  compact, highefficiency power-delivery solutions with high-precision

space             ^

> +  output voltages and excellent transient response

period needed

> +
> +  Datasheets:
> +    https://datasheets.maximintegrated.com/en/ds/MAX20730.pdf
> +    https://datasheets.maximintegrated.com/en/ds/MAX20734.pdf
> +    https://datasheets.maximintegrated.com/en/ds/MAX20743.pdf
> +
> +properties:
> +  compatible:
> +    enum:
> +      - maxim,max20730
> +      - maxim,max20734
> +      - maxim,max20743
> +
> +  reg:
> +    maxItems: 1
> +
> +  vout-voltage-divider:
> +    description: |
> +      If voltage divider presents at vout, the voltage at voltage sensor pin
> +      will be scaled. The properties will convert the raw reading to a more
> +      meaningful number if voltage divider presents. It has two numbers,

s/presents/present/

> +      the first number is the output resistor, the second number is the total
> +      resistance. Therefore, the adjusted vout is equal to
> +      Vout = Vout * output_resistance / total resistance.
> +    $ref: /schemas/types.yaml#/definitions/uint32-array
> +    minItems: 2
> +    maxItems: 2
> +
> +required:
> +  - compatible
> +  - reg

additionalProperties: false

> +
> +examples:
> +  - |
> +    i2c {
> +      #address-cells = <1>;
> +      #size-cells = <0>;
> +
> +      max20730@10 {
> +        compatible = "maxim,max20730";
> +        reg = <0x10>;
> +        vout-voltage-divider = <1000 2000>; // vout would be scaled to 0.5
> +      };
> +    };
> -- 
> 2.28.0.681.g6f77f65b4e-goog
> 

Re: [PATCH v3 2/2] hwmon: pmbus: max20730: adjust the vout reading given voltage divider

[Guenter Roeck]

On Thu, Sep 24, 2020 at 09:54:44PM +0000, Chu Lin wrote:
> Problem:
> We use voltage dividers so that the voltage presented at the voltage
> sense pins is confusing. We might need to convert these readings to more
> meaningful readings given the voltage divider.
> 
> Solution:
> Read the voltage divider resistance from dts and convert the voltage
> reading to a more meaningful reading.
> 
> Testing:
> max20730 with voltage divider
> 
> Signed-off-by: Chu Lin <linchuyuan@google.com>
> ---

<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 will hold up both this patch as well as all other
patches which I still have to review.

Please keep this in mind when submitting patch revisions without change log.
</Formletter>

Worse, this is v3, and I had given v2 a Reviewed-by: tag which was dropped.
This means I have to compare the two versions to figure out what changed,
probably just to find out that nothing has changed since v2.

Patches like this are the reason why various patches won't make it into
the next kernel release. Sorry, I just don't have as much time as people
seem to think I have.

Guenter

>  drivers/hwmon/pmbus/max20730.c | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
> 
> diff --git a/drivers/hwmon/pmbus/max20730.c b/drivers/hwmon/pmbus/max20730.c
> index a151a2b588a5..fbf2f1e6c969 100644
> --- a/drivers/hwmon/pmbus/max20730.c
> +++ b/drivers/hwmon/pmbus/max20730.c
> @@ -31,6 +31,7 @@ struct max20730_data {
>  	struct pmbus_driver_info info;
>  	struct mutex lock;	/* Used to protect against parallel writes */
>  	u16 mfr_devset1;
> +	u32 vout_voltage_divider[2];
>  };
>  
>  #define to_max20730_data(x)  container_of(x, struct max20730_data, info)
> @@ -114,6 +115,14 @@ static int max20730_read_word_data(struct i2c_client *client, int page,
>  		max_c = max_current[data->id][(data->mfr_devset1 >> 5) & 0x3];
>  		ret = val_to_direct(max_c, PSC_CURRENT_OUT, info);
>  		break;
> +	case PMBUS_READ_VOUT:
> +		ret = pmbus_read_word_data(client, page, phase, reg);
> +		if (ret > 0 && data->vout_voltage_divider[0] && data->vout_voltage_divider[1]) {
> +			u64 temp = DIV_ROUND_CLOSEST_ULL((u64)ret * data->vout_voltage_divider[1],
> +							 data->vout_voltage_divider[0]);
> +			ret = clamp_val(temp, 0, 0xffff);
> +		}
> +		break;
>  	default:
>  		ret = -ENODATA;
>  		break;
> @@ -364,6 +373,15 @@ static int max20730_probe(struct i2c_client *client,
>  	data->id = chip_id;
>  	mutex_init(&data->lock);
>  	memcpy(&data->info, &max20730_info[chip_id], sizeof(data->info));
> +	if (of_property_read_u32_array(client->dev.of_node, "vout-voltage-divider",
> +				       data->vout_voltage_divider,
> +				       ARRAY_SIZE(data->vout_voltage_divider)) != 0)
> +		memset(data->vout_voltage_divider, 0, sizeof(data->vout_voltage_divider));
> +	if (data->vout_voltage_divider[1] < data->vout_voltage_divider[0]) {
> +		dev_err(dev,
> +			"The total resistance of voltage divider is less than output resistance\n");
> +		return -ENODEV;
> +	}
>  
>  	ret = i2c_smbus_read_word_data(client, MAX20730_MFR_DEVSET1);
>  	if (ret < 0)