[PATCH 0/3] media: i2c: ak7375: Add regulator management

[PATCH 0/3] media: i2c: ak7375: Add regulator management

[Yassine Oudjana]

From: Yassine Oudjana <y.oudjana@protonmail.com>

This series adds needed regulator management for the AK7375 VCM.
A DT schema conversion is made before adding new properties.

Yassine Oudjana (3):
  media: dt-bindings: ak7375: Convert to DT schema
  media: dt-bindings: ak7375: Add supplies
  media: i2c: ak7375: Add regulator management

 .../devicetree/bindings/media/i2c/ak7375.txt  |  8 ---
 .../devicetree/bindings/media/i2c/ak7375.yaml | 52 +++++++++++++++++++
 MAINTAINERS                                   |  2 +-
 drivers/media/i2c/ak7375.c                    | 39 ++++++++++++++
 4 files changed, 92 insertions(+), 9 deletions(-)
 delete mode 100644 Documentation/devicetree/bindings/media/i2c/ak7375.txt
 create mode 100644 Documentation/devicetree/bindings/media/i2c/ak7375.yaml

-- 
2.37.0

[PATCH 1/3] media: dt-bindings: ak7375: Convert to DT schema

[Yassine Oudjana]

From: Yassine Oudjana <y.oudjana@protonmail.com>

Convert DT bindings document for AKM AK7375 VCM to DT schema
format and add an example.

Signed-off-by: Yassine Oudjana <y.oudjana@protonmail.com>
---
 .../devicetree/bindings/media/i2c/ak7375.txt  |  8 ----
 .../devicetree/bindings/media/i2c/ak7375.yaml | 41 +++++++++++++++++++
 MAINTAINERS                                   |  2 +-
 3 files changed, 42 insertions(+), 9 deletions(-)
 delete mode 100644 Documentation/devicetree/bindings/media/i2c/ak7375.txt
 create mode 100644 Documentation/devicetree/bindings/media/i2c/ak7375.yaml

diff --git a/Documentation/devicetree/bindings/media/i2c/ak7375.txt b/Documentation/devicetree/bindings/media/i2c/ak7375.txt
deleted file mode 100644
index aa3e24b41241..000000000000
--- a/Documentation/devicetree/bindings/media/i2c/ak7375.txt
+++ /dev/null
@@ -1,8 +0,0 @@
-Asahi Kasei Microdevices AK7375 voice coil lens driver
-
-AK7375 is a camera voice coil lens.
-
-Mandatory properties:
-
-- compatible: "asahi-kasei,ak7375"
-- reg: I2C slave address
diff --git a/Documentation/devicetree/bindings/media/i2c/ak7375.yaml b/Documentation/devicetree/bindings/media/i2c/ak7375.yaml
new file mode 100644
index 000000000000..4fc216846ae7
--- /dev/null
+++ b/Documentation/devicetree/bindings/media/i2c/ak7375.yaml
@@ -0,0 +1,41 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/media/i2c/ak7375.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Asahi Kasei Microdevices AK7375 voice coil lens actuator
+
+maintainers:
+  - Tianshu Qiu <tian.shu.qiu@intel.com>
+
+description:
+  AK7375 is a voice coil motor (VCM) camera lens actuator that
+  is controlled over I2C.
+
+properties:
+  compatible:
+    const: asahi-kasei,ak7375
+
+  reg:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+
+additionalProperties: false
+
+examples:
+  - |
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        ak7375: camera-lens@c {
+            compatible = "asahi-kasei,ak7375";
+            reg = <0x0c>;
+        };
+    };
+
+...
diff --git a/MAINTAINERS b/MAINTAINERS
index a97fef8c131d..19faf9ce8258 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -3063,7 +3063,7 @@ M:	Tianshu Qiu <tian.shu.qiu@intel.com>
 L:	linux-media@vger.kernel.org
 S:	Maintained
 T:	git git://linuxtv.org/media_tree.git
-F:	Documentation/devicetree/bindings/media/i2c/ak7375.txt
+F:	Documentation/devicetree/bindings/media/i2c/ak7375.yaml
 F:	drivers/media/i2c/ak7375.c
 
 ASAHI KASEI AK8974 DRIVER
-- 
2.37.0

[PATCH 2/3] media: dt-bindings: ak7375: Add supplies

[Yassine Oudjana]

From: Yassine Oudjana <y.oudjana@protonmail.com>

Add supply properties to describe regulators needed to power
the AK7375 VCM.

Signed-off-by: Yassine Oudjana <y.oudjana@protonmail.com>
---
 .../devicetree/bindings/media/i2c/ak7375.yaml         | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/Documentation/devicetree/bindings/media/i2c/ak7375.yaml b/Documentation/devicetree/bindings/media/i2c/ak7375.yaml
index 4fc216846ae7..baa91de55927 100644
--- a/Documentation/devicetree/bindings/media/i2c/ak7375.yaml
+++ b/Documentation/devicetree/bindings/media/i2c/ak7375.yaml
@@ -20,9 +20,17 @@ properties:
   reg:
     maxItems: 1
 
+  vdd-supply:
+    description: VDD supply
+
+  vio-supply:
+    description: I/O pull-up supply
+
 required:
   - compatible
   - reg
+  - vdd-supply
+  - vio-supply
 
 additionalProperties: false
 
@@ -35,6 +43,9 @@ examples:
         ak7375: camera-lens@c {
             compatible = "asahi-kasei,ak7375";
             reg = <0x0c>;
+
+            vdd-supply = <&vreg_l23a_2p8>;
+            vio-supply = <&vreg_lvs1a_1p8>;
         };
     };
 
-- 
2.37.0

[PATCH 3/3] media: i2c: ak7375: Add regulator management

[Yassine Oudjana]

From: Yassine Oudjana <y.oudjana@protonmail.com>

Make the driver get needed regulators on probe and enable/disable
them on runtime PM callbacks.

Signed-off-by: Yassine Oudjana <y.oudjana@protonmail.com>
---
 drivers/media/i2c/ak7375.c | 39 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/drivers/media/i2c/ak7375.c b/drivers/media/i2c/ak7375.c
index 40b1a4aa846c..59d5cb00e3ba 100644
--- a/drivers/media/i2c/ak7375.c
+++ b/drivers/media/i2c/ak7375.c
@@ -6,6 +6,7 @@
 #include <linux/i2c.h>
 #include <linux/module.h>
 #include <linux/pm_runtime.h>
+#include <linux/regulator/consumer.h>
 #include <media/v4l2-ctrls.h>
 #include <media/v4l2-device.h>
 
@@ -23,17 +24,32 @@
  */
 #define AK7375_CTRL_STEPS	64
 #define AK7375_CTRL_DELAY_US	1000
+/*
+ * The vcm takes around 3 ms to power on and start taking
+ * I2C messages. This value was found experimentally due to
+ * lack of documentation. 2 ms is added as a safety margin.
+ */
+#define AK7375_POWER_DELAY_US	5000
 
 #define AK7375_REG_POSITION	0x0
 #define AK7375_REG_CONT		0x2
 #define AK7375_MODE_ACTIVE	0x0
 #define AK7375_MODE_STANDBY	0x40
 
+static const char * const ak7375_supply_names[] = {
+	"vdd",
+	"vio",
+};
+
+#define AK7375_NUM_SUPPLIES ARRAY_SIZE(ak7375_supply_names)
+
 /* ak7375 device structure */
 struct ak7375_device {
 	struct v4l2_ctrl_handler ctrls_vcm;
 	struct v4l2_subdev sd;
 	struct v4l2_ctrl *focus;
+	struct regulator_bulk_data supplies[AK7375_NUM_SUPPLIES];
+
 	/* active or standby mode */
 	bool active;
 };
@@ -132,6 +148,7 @@ static int ak7375_init_controls(struct ak7375_device *dev_vcm)
 static int ak7375_probe(struct i2c_client *client)
 {
 	struct ak7375_device *ak7375_dev;
+	int i;
 	int ret;
 
 	ak7375_dev = devm_kzalloc(&client->dev, sizeof(*ak7375_dev),
@@ -139,6 +156,17 @@ static int ak7375_probe(struct i2c_client *client)
 	if (!ak7375_dev)
 		return -ENOMEM;
 
+	for (i = 0; i < AK7375_NUM_SUPPLIES; i++)
+		ak7375_dev->supplies[i].supply = ak7375_supply_names[i];
+
+	ret = devm_regulator_bulk_get(&client->dev, AK7375_NUM_SUPPLIES,
+				      ak7375_dev->supplies);
+	if (ret) {
+		dev_err(&client->dev, "Failed to get regulators: %pe",
+			ERR_PTR(ret));
+		return ret;
+	}
+
 	v4l2_i2c_subdev_init(&ak7375_dev->sd, client, &ak7375_ops);
 	ak7375_dev->sd.flags |= V4L2_SUBDEV_FL_HAS_DEVNODE;
 	ak7375_dev->sd.internal_ops = &ak7375_int_ops;
@@ -210,6 +238,10 @@ static int __maybe_unused ak7375_vcm_suspend(struct device *dev)
 	if (ret)
 		dev_err(dev, "%s I2C failure: %d\n", __func__, ret);
 
+	ret = regulator_bulk_disable(AK7375_NUM_SUPPLIES, ak7375_dev->supplies);
+	if (ret)
+		return ret;
+
 	ak7375_dev->active = false;
 
 	return 0;
@@ -230,6 +262,13 @@ static int __maybe_unused ak7375_vcm_resume(struct device *dev)
 	if (ak7375_dev->active)
 		return 0;
 
+	ret = regulator_bulk_enable(AK7375_NUM_SUPPLIES, ak7375_dev->supplies);
+	if (ret)
+		return ret;
+
+	/* Wait for vcm to become ready */
+	usleep_range(AK7375_POWER_DELAY_US, AK7375_POWER_DELAY_US + 10);
+
 	ret = ak7375_i2c_write(ak7375_dev, AK7375_REG_CONT,
 		AK7375_MODE_ACTIVE, 1);
 	if (ret) {
-- 
2.37.0

Re: [PATCH 1/3] media: dt-bindings: ak7375: Convert to DT schema

[Krzysztof Kozlowski]

On 11/07/2022 06:28, Yassine Oudjana wrote:
> From: Yassine Oudjana <y.oudjana@protonmail.com>
> 
> Convert DT bindings document for AKM AK7375 VCM to DT schema
> format and add an example.
> 
> Signed-off-by: Yassine Oudjana <y.oudjana@protonmail.com>
> ---
>  .../devicetree/bindings/media/i2c/ak7375.txt  |  8 ----
>  .../devicetree/bindings/media/i2c/ak7375.yaml | 41 +++++++++++++++++++
>  MAINTAINERS                                   |  2 +-
>  3 files changed, 42 insertions(+), 9 deletions(-)
>  delete mode 100644 Documentation/devicetree/bindings/media/i2c/ak7375.txt
>  create mode 100644 Documentation/devicetree/bindings/media/i2c/ak7375.yaml
> 
> diff --git a/Documentation/devicetree/bindings/media/i2c/ak7375.txt b/Documentation/devicetree/bindings/media/i2c/ak7375.txt
> deleted file mode 100644
> index aa3e24b41241..000000000000
> --- a/Documentation/devicetree/bindings/media/i2c/ak7375.txt
> +++ /dev/null
> @@ -1,8 +0,0 @@
> -Asahi Kasei Microdevices AK7375 voice coil lens driver
> -
> -AK7375 is a camera voice coil lens.
> -
> -Mandatory properties:
> -
> -- compatible: "asahi-kasei,ak7375"
> -- reg: I2C slave address
> diff --git a/Documentation/devicetree/bindings/media/i2c/ak7375.yaml b/Documentation/devicetree/bindings/media/i2c/ak7375.yaml
> new file mode 100644
> index 000000000000..4fc216846ae7
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/media/i2c/ak7375.yaml
> @@ -0,0 +1,41 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/media/i2c/ak7375.yaml#

Include vendor prefix in the file name, so:
asahi-kasei,ak7375.yaml


Best regards,
Krzysztof

Re: [PATCH 2/3] media: dt-bindings: ak7375: Add supplies

[Krzysztof Kozlowski]

On 11/07/2022 06:28, Yassine Oudjana wrote:
> From: Yassine Oudjana <y.oudjana@protonmail.com>
> 
> Add supply properties to describe regulators needed to power
> the AK7375 VCM.
> 
> Signed-off-by: Yassine Oudjana <y.oudjana@protonmail.com>
> ---


Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>


Best regards,
Krzysztof

Re: [PATCH 3/3] media: i2c: ak7375: Add regulator management

[Jacopo Mondi]

Hello Yassine

On Mon, Jul 11, 2022 at 08:28:39AM +0400, Yassine Oudjana wrote:
> From: Yassine Oudjana <y.oudjana@protonmail.com>
>
> Make the driver get needed regulators on probe and enable/disable
> them on runtime PM callbacks.
>
> Signed-off-by: Yassine Oudjana <y.oudjana@protonmail.com>
> ---
>  drivers/media/i2c/ak7375.c | 39 ++++++++++++++++++++++++++++++++++++++
>  1 file changed, 39 insertions(+)
>
> diff --git a/drivers/media/i2c/ak7375.c b/drivers/media/i2c/ak7375.c
> index 40b1a4aa846c..59d5cb00e3ba 100644
> --- a/drivers/media/i2c/ak7375.c
> +++ b/drivers/media/i2c/ak7375.c
> @@ -6,6 +6,7 @@
>  #include <linux/i2c.h>
>  #include <linux/module.h>
>  #include <linux/pm_runtime.h>
> +#include <linux/regulator/consumer.h>
>  #include <media/v4l2-ctrls.h>
>  #include <media/v4l2-device.h>
>
> @@ -23,17 +24,32 @@
>   */
>  #define AK7375_CTRL_STEPS	64
>  #define AK7375_CTRL_DELAY_US	1000
> +/*
> + * The vcm takes around 3 ms to power on and start taking
> + * I2C messages. This value was found experimentally due to
> + * lack of documentation. 2 ms is added as a safety margin.
> + */
> +#define AK7375_POWER_DELAY_US	5000
>
>  #define AK7375_REG_POSITION	0x0
>  #define AK7375_REG_CONT		0x2
>  #define AK7375_MODE_ACTIVE	0x0
>  #define AK7375_MODE_STANDBY	0x40
>
> +static const char * const ak7375_supply_names[] = {
> +	"vdd",
> +	"vio",
> +};
> +
> +#define AK7375_NUM_SUPPLIES ARRAY_SIZE(ak7375_supply_names)
> +
>  /* ak7375 device structure */
>  struct ak7375_device {
>  	struct v4l2_ctrl_handler ctrls_vcm;
>  	struct v4l2_subdev sd;
>  	struct v4l2_ctrl *focus;
> +	struct regulator_bulk_data supplies[AK7375_NUM_SUPPLIES];
> +
>  	/* active or standby mode */
>  	bool active;
>  };
> @@ -132,6 +148,7 @@ static int ak7375_init_controls(struct ak7375_device *dev_vcm)
>  static int ak7375_probe(struct i2c_client *client)
>  {
>  	struct ak7375_device *ak7375_dev;
> +	int i;

I would have moved this one down to maintain variable declaration
in the in-famous reverse-xmas-tree ordering. Up to you.

>  	int ret;
>
>  	ak7375_dev = devm_kzalloc(&client->dev, sizeof(*ak7375_dev),
> @@ -139,6 +156,17 @@ static int ak7375_probe(struct i2c_client *client)
>  	if (!ak7375_dev)
>  		return -ENOMEM;
>
> +	for (i = 0; i < AK7375_NUM_SUPPLIES; i++)
> +		ak7375_dev->supplies[i].supply = ak7375_supply_names[i];
> +
> +	ret = devm_regulator_bulk_get(&client->dev, AK7375_NUM_SUPPLIES,
> +				      ak7375_dev->supplies);
> +	if (ret) {
> +		dev_err(&client->dev, "Failed to get regulators: %pe",
> +			ERR_PTR(ret));
> +		return ret;
> +	}
> +
>  	v4l2_i2c_subdev_init(&ak7375_dev->sd, client, &ak7375_ops);
>  	ak7375_dev->sd.flags |= V4L2_SUBDEV_FL_HAS_DEVNODE;
>  	ak7375_dev->sd.internal_ops = &ak7375_int_ops;
> @@ -210,6 +238,10 @@ static int __maybe_unused ak7375_vcm_suspend(struct device *dev)
>  	if (ret)
>  		dev_err(dev, "%s I2C failure: %d\n", __func__, ret);
>
> +	ret = regulator_bulk_disable(AK7375_NUM_SUPPLIES, ak7375_dev->supplies);
> +	if (ret)
> +		return ret;
> +
>  	ak7375_dev->active = false;
>
>  	return 0;
> @@ -230,6 +262,13 @@ static int __maybe_unused ak7375_vcm_resume(struct device *dev)
>  	if (ak7375_dev->active)
>  		return 0;
>
> +	ret = regulator_bulk_enable(AK7375_NUM_SUPPLIES, ak7375_dev->supplies);
> +	if (ret)
> +		return ret;
> +
> +	/* Wait for vcm to become ready */
> +	usleep_range(AK7375_POWER_DELAY_US, AK7375_POWER_DELAY_US + 10);
> +

Isn't 10usec a very small delay to be given to usleep_range() for a
delay of at least 3msec ? Also assuming 5msec just to be safe seems a
little arbitrary. Adding 2 milliseconds in the wakeup path introduces
a non-negligible delay.

It's likely a detail, but according to Documentation/timers/timers-howto.rst

        Since usleep_range is built on top of hrtimers, the
        wakeup will be very precise (ish), thus a simple
        usleep function would likely introduce a large number
        of undesired interrupts.

        With the introduction of a range, the scheduler is
        free to coalesce your wakeup with any other wakeup
        that may have happened for other reasons, or at the
        worst case, fire an interrupt for your upper bound.

        The larger a range you supply, the greater a chance
        that you will not trigger an interrupt; this should
        be balanced with what is an acceptable upper bound on
        delay / performance for your specific code path. Exact
        tolerances here are very situation specific, thus it
        is left to the caller to determine a reasonable range.

If you have a min of 3msec I would try with a range of (3000, 3500).
What do you think ?

>  	ret = ak7375_i2c_write(ak7375_dev, AK7375_REG_CONT,
>  		AK7375_MODE_ACTIVE, 1);
>  	if (ret) {
> --
> 2.37.0
>

Re: [PATCH 3/3] media: i2c: ak7375: Add regulator management

[Yassine Oudjana]

On Mon, Jul 11 2022 at 15:34:23 +0200, Jacopo Mondi <jacopo@jmondi.org> 
wrote:
> Hello Yassine
> 
> On Mon, Jul 11, 2022 at 08:28:39AM +0400, Yassine Oudjana wrote:
>>  From: Yassine Oudjana <y.oudjana@protonmail.com>
>> 
>>  Make the driver get needed regulators on probe and enable/disable
>>  them on runtime PM callbacks.
>> 
>>  Signed-off-by: Yassine Oudjana <y.oudjana@protonmail.com>
>>  ---
>>   drivers/media/i2c/ak7375.c | 39 
>> ++++++++++++++++++++++++++++++++++++++
>>   1 file changed, 39 insertions(+)
>> 
>>  diff --git a/drivers/media/i2c/ak7375.c b/drivers/media/i2c/ak7375.c
>>  index 40b1a4aa846c..59d5cb00e3ba 100644
>>  --- a/drivers/media/i2c/ak7375.c
>>  +++ b/drivers/media/i2c/ak7375.c
>>  @@ -6,6 +6,7 @@
>>   #include <linux/i2c.h>
>>   #include <linux/module.h>
>>   #include <linux/pm_runtime.h>
>>  +#include <linux/regulator/consumer.h>
>>   #include <media/v4l2-ctrls.h>
>>   #include <media/v4l2-device.h>
>> 
>>  @@ -23,17 +24,32 @@
>>    */
>>   #define AK7375_CTRL_STEPS	64
>>   #define AK7375_CTRL_DELAY_US	1000
>>  +/*
>>  + * The vcm takes around 3 ms to power on and start taking
>>  + * I2C messages. This value was found experimentally due to
>>  + * lack of documentation. 2 ms is added as a safety margin.
>>  + */
>>  +#define AK7375_POWER_DELAY_US	5000
>> 
>>   #define AK7375_REG_POSITION	0x0
>>   #define AK7375_REG_CONT		0x2
>>   #define AK7375_MODE_ACTIVE	0x0
>>   #define AK7375_MODE_STANDBY	0x40
>> 
>>  +static const char * const ak7375_supply_names[] = {
>>  +	"vdd",
>>  +	"vio",
>>  +};
>>  +
>>  +#define AK7375_NUM_SUPPLIES ARRAY_SIZE(ak7375_supply_names)
>>  +
>>   /* ak7375 device structure */
>>   struct ak7375_device {
>>   	struct v4l2_ctrl_handler ctrls_vcm;
>>   	struct v4l2_subdev sd;
>>   	struct v4l2_ctrl *focus;
>>  +	struct regulator_bulk_data supplies[AK7375_NUM_SUPPLIES];
>>  +
>>   	/* active or standby mode */
>>   	bool active;
>>   };
>>  @@ -132,6 +148,7 @@ static int ak7375_init_controls(struct 
>> ak7375_device *dev_vcm)
>>   static int ak7375_probe(struct i2c_client *client)
>>   {
>>   	struct ak7375_device *ak7375_dev;
>>  +	int i;
> 
> I would have moved this one down to maintain variable declaration
> in the in-famous reverse-xmas-tree ordering. Up to you.

I'm used to declaring variables in the order of first use,
but I don't really mind it either way. I'll move it down.

> 
>>   	int ret;
>> 
>>   	ak7375_dev = devm_kzalloc(&client->dev, sizeof(*ak7375_dev),
>>  @@ -139,6 +156,17 @@ static int ak7375_probe(struct i2c_client 
>> *client)
>>   	if (!ak7375_dev)
>>   		return -ENOMEM;
>> 
>>  +	for (i = 0; i < AK7375_NUM_SUPPLIES; i++)
>>  +		ak7375_dev->supplies[i].supply = ak7375_supply_names[i];
>>  +
>>  +	ret = devm_regulator_bulk_get(&client->dev, AK7375_NUM_SUPPLIES,
>>  +				      ak7375_dev->supplies);
>>  +	if (ret) {
>>  +		dev_err(&client->dev, "Failed to get regulators: %pe",
>>  +			ERR_PTR(ret));
>>  +		return ret;
>>  +	}
>>  +
>>   	v4l2_i2c_subdev_init(&ak7375_dev->sd, client, &ak7375_ops);
>>   	ak7375_dev->sd.flags |= V4L2_SUBDEV_FL_HAS_DEVNODE;
>>   	ak7375_dev->sd.internal_ops = &ak7375_int_ops;
>>  @@ -210,6 +238,10 @@ static int __maybe_unused 
>> ak7375_vcm_suspend(struct device *dev)
>>   	if (ret)
>>   		dev_err(dev, "%s I2C failure: %d\n", __func__, ret);
>> 
>>  +	ret = regulator_bulk_disable(AK7375_NUM_SUPPLIES, 
>> ak7375_dev->supplies);
>>  +	if (ret)
>>  +		return ret;
>>  +
>>   	ak7375_dev->active = false;
>> 
>>   	return 0;
>>  @@ -230,6 +262,13 @@ static int __maybe_unused 
>> ak7375_vcm_resume(struct device *dev)
>>   	if (ak7375_dev->active)
>>   		return 0;
>> 
>>  +	ret = regulator_bulk_enable(AK7375_NUM_SUPPLIES, 
>> ak7375_dev->supplies);
>>  +	if (ret)
>>  +		return ret;
>>  +
>>  +	/* Wait for vcm to become ready */
>>  +	usleep_range(AK7375_POWER_DELAY_US, AK7375_POWER_DELAY_US + 10);
>>  +
> 
> Isn't 10usec a very small delay to be given to usleep_range() for a
> delay of at least 3msec ? Also assuming 5msec just to be safe seems a
> little arbitrary. Adding 2 milliseconds in the wakeup path introduces
> a non-negligible delay.

I must admit that I didn't give it too much thought. I just
did it similar to the other delay used in this driver
(AK7375_CTRL_DELAY_US). As for adding 2ms, I don't know what
the worst case wake-up time is since I don't have a datasheet
on hand, so I just wanted to stay safe. Also, this driver
doesn't really recover if it fails to resume (which is what
used to happen before adding a delay). Rounding up to 5ms
felt good enough.

> 
> It's likely a detail, but according to 
> Documentation/timers/timers-howto.rst
> 
>         Since usleep_range is built on top of hrtimers, the
>         wakeup will be very precise (ish), thus a simple
>         usleep function would likely introduce a large number
>         of undesired interrupts.
> 
>         With the introduction of a range, the scheduler is
>         free to coalesce your wakeup with any other wakeup
>         that may have happened for other reasons, or at the
>         worst case, fire an interrupt for your upper bound.
> 
>         The larger a range you supply, the greater a chance
>         that you will not trigger an interrupt; this should
>         be balanced with what is an acceptable upper bound on
>         delay / performance for your specific code path. Exact
>         tolerances here are very situation specific, thus it
>         is left to the caller to determine a reasonable range.
> 
> If you have a min of 3msec I would try with a range of (3000, 3500).
> What do you think ?

Seems good. I haven't yet had it fail to power on within 3ms of
turning on regulators so I guess there is no reason to worry about it.

>> 
>>   	ret = ak7375_i2c_write(ak7375_dev, AK7375_REG_CONT,
>>   		AK7375_MODE_ACTIVE, 1);
>>   	if (ret) {
>>  --
>>  2.37.0
> 

Thanks for the review,
Yassine

Re: [PATCH 3/3] media: i2c: ak7375: Add regulator management

[Jacopo Mondi]

Hi Yassine

On Mon, Jul 11, 2022 at 06:08:53PM +0400, Yassine Oudjana wrote:
>
> On Mon, Jul 11 2022 at 15:34:23 +0200, Jacopo Mondi <jacopo@jmondi.org>
> wrote:
> > Hello Yassine
> >
> > On Mon, Jul 11, 2022 at 08:28:39AM +0400, Yassine Oudjana wrote:
> > >  From: Yassine Oudjana <y.oudjana@protonmail.com>
> > >
> > >  Make the driver get needed regulators on probe and enable/disable
> > >  them on runtime PM callbacks.
> > >
> > >  Signed-off-by: Yassine Oudjana <y.oudjana@protonmail.com>
> > >  ---
> > >   drivers/media/i2c/ak7375.c | 39
> > > ++++++++++++++++++++++++++++++++++++++
> > >   1 file changed, 39 insertions(+)
> > >
> > >  diff --git a/drivers/media/i2c/ak7375.c b/drivers/media/i2c/ak7375.c
> > >  index 40b1a4aa846c..59d5cb00e3ba 100644
> > >  --- a/drivers/media/i2c/ak7375.c
> > >  +++ b/drivers/media/i2c/ak7375.c
> > >  @@ -6,6 +6,7 @@
> > >   #include <linux/i2c.h>
> > >   #include <linux/module.h>
> > >   #include <linux/pm_runtime.h>
> > >  +#include <linux/regulator/consumer.h>
> > >   #include <media/v4l2-ctrls.h>
> > >   #include <media/v4l2-device.h>
> > >
> > >  @@ -23,17 +24,32 @@
> > >    */
> > >   #define AK7375_CTRL_STEPS	64
> > >   #define AK7375_CTRL_DELAY_US	1000
> > >  +/*
> > >  + * The vcm takes around 3 ms to power on and start taking
> > >  + * I2C messages. This value was found experimentally due to
> > >  + * lack of documentation. 2 ms is added as a safety margin.
> > >  + */
> > >  +#define AK7375_POWER_DELAY_US	5000
> > >
> > >   #define AK7375_REG_POSITION	0x0
> > >   #define AK7375_REG_CONT		0x2
> > >   #define AK7375_MODE_ACTIVE	0x0
> > >   #define AK7375_MODE_STANDBY	0x40
> > >
> > >  +static const char * const ak7375_supply_names[] = {
> > >  +	"vdd",
> > >  +	"vio",
> > >  +};
> > >  +
> > >  +#define AK7375_NUM_SUPPLIES ARRAY_SIZE(ak7375_supply_names)
> > >  +
> > >   /* ak7375 device structure */
> > >   struct ak7375_device {
> > >   	struct v4l2_ctrl_handler ctrls_vcm;
> > >   	struct v4l2_subdev sd;
> > >   	struct v4l2_ctrl *focus;
> > >  +	struct regulator_bulk_data supplies[AK7375_NUM_SUPPLIES];
> > >  +
> > >   	/* active or standby mode */
> > >   	bool active;
> > >   };
> > >  @@ -132,6 +148,7 @@ static int ak7375_init_controls(struct
> > > ak7375_device *dev_vcm)
> > >   static int ak7375_probe(struct i2c_client *client)
> > >   {
> > >   	struct ak7375_device *ak7375_dev;
> > >  +	int i;
> >
> > I would have moved this one down to maintain variable declaration
> > in the in-famous reverse-xmas-tree ordering. Up to you.
>
> I'm used to declaring variables in the order of first use,
> but I don't really mind it either way. I'll move it down.
>
> >
> > >   	int ret;
> > >
> > >   	ak7375_dev = devm_kzalloc(&client->dev, sizeof(*ak7375_dev),
> > >  @@ -139,6 +156,17 @@ static int ak7375_probe(struct i2c_client
> > > *client)
> > >   	if (!ak7375_dev)
> > >   		return -ENOMEM;
> > >
> > >  +	for (i = 0; i < AK7375_NUM_SUPPLIES; i++)
> > >  +		ak7375_dev->supplies[i].supply = ak7375_supply_names[i];
> > >  +
> > >  +	ret = devm_regulator_bulk_get(&client->dev, AK7375_NUM_SUPPLIES,
> > >  +				      ak7375_dev->supplies);
> > >  +	if (ret) {
> > >  +		dev_err(&client->dev, "Failed to get regulators: %pe",
> > >  +			ERR_PTR(ret));
> > >  +		return ret;
> > >  +	}
> > >  +
> > >   	v4l2_i2c_subdev_init(&ak7375_dev->sd, client, &ak7375_ops);
> > >   	ak7375_dev->sd.flags |= V4L2_SUBDEV_FL_HAS_DEVNODE;
> > >   	ak7375_dev->sd.internal_ops = &ak7375_int_ops;
> > >  @@ -210,6 +238,10 @@ static int __maybe_unused
> > > ak7375_vcm_suspend(struct device *dev)
> > >   	if (ret)
> > >   		dev_err(dev, "%s I2C failure: %d\n", __func__, ret);
> > >
> > >  +	ret = regulator_bulk_disable(AK7375_NUM_SUPPLIES,
> > > ak7375_dev->supplies);
> > >  +	if (ret)
> > >  +		return ret;
> > >  +
> > >   	ak7375_dev->active = false;
> > >
> > >   	return 0;
> > >  @@ -230,6 +262,13 @@ static int __maybe_unused
> > > ak7375_vcm_resume(struct device *dev)
> > >   	if (ak7375_dev->active)
> > >   		return 0;
> > >
> > >  +	ret = regulator_bulk_enable(AK7375_NUM_SUPPLIES,
> > > ak7375_dev->supplies);
> > >  +	if (ret)
> > >  +		return ret;
> > >  +
> > >  +	/* Wait for vcm to become ready */
> > >  +	usleep_range(AK7375_POWER_DELAY_US, AK7375_POWER_DELAY_US + 10);
> > >  +
> >
> > Isn't 10usec a very small delay to be given to usleep_range() for a
> > delay of at least 3msec ? Also assuming 5msec just to be safe seems a
> > little arbitrary. Adding 2 milliseconds in the wakeup path introduces
> > a non-negligible delay.
>
> I must admit that I didn't give it too much thought. I just
> did it similar to the other delay used in this driver
> (AK7375_CTRL_DELAY_US). As for adding 2ms, I don't know what
> the worst case wake-up time is since I don't have a datasheet
> on hand, so I just wanted to stay safe. Also, this driver

Oh sorry, I missed in the comment the value was found experimentally
an it's not documented..

> doesn't really recover if it fails to resume (which is what
> used to happen before adding a delay). Rounding up to 5ms
> felt good enough.
>
> >
> > It's likely a detail, but according to
> > Documentation/timers/timers-howto.rst
> >
> >         Since usleep_range is built on top of hrtimers, the
> >         wakeup will be very precise (ish), thus a simple
> >         usleep function would likely introduce a large number
> >         of undesired interrupts.
> >
> >         With the introduction of a range, the scheduler is
> >         free to coalesce your wakeup with any other wakeup
> >         that may have happened for other reasons, or at the
> >         worst case, fire an interrupt for your upper bound.
> >
> >         The larger a range you supply, the greater a chance
> >         that you will not trigger an interrupt; this should
> >         be balanced with what is an acceptable upper bound on
> >         delay / performance for your specific code path. Exact
> >         tolerances here are very situation specific, thus it
> >         is left to the caller to determine a reasonable range.
> >
> > If you have a min of 3msec I would try with a range of (3000, 3500).
> > What do you think ?
>
> Seems good. I haven't yet had it fail to power on within 3ms of
> turning on regulators so I guess there is no reason to worry about it.
>

Ok then :) There's anyway a comment that says the value comes from
practical experience, so if anything bad happens, it's easy to track
it down to that

Thanks
  j

> > >
> > >   	ret = ak7375_i2c_write(ak7375_dev, AK7375_REG_CONT,
> > >   		AK7375_MODE_ACTIVE, 1);
> > >   	if (ret) {
> > >  --
> > >  2.37.0
> >
>
> Thanks for the review,
> Yassine
>
>