Re: [PATCH v2 3/3] media: i2c: ak7375: Add regulator management

[Yassine Oudjana]

On Wed, Jul 13 2022 at 09:39:51 +0200, Jacopo Mondi <jacopo@xxxxxxxxxx> 
wrote:
> Hi Yassine
>
> On Mon, Jul 11, 2022 at 06:40:39PM +0400, Yassine Oudjana wrote:
> >  From: Yassine Oudjana <y.oudjana@xxxxxxxxxxxxxx>
> >
> >  Make the driver get needed regulators on probe and enable/disable
> >  them on runtime PM callbacks.
> >
> >  Signed-off-by: Yassine Oudjana <y.oudjana@xxxxxxxxxxxxxx>
>
> Have you seen this ?
> https://github.com/ArduCAM/IMX519_AK7375/blob/main/AK7375/0002-media-i2c-ak7375-driver-add-optional-regulator-suppo.patch#L172
>
> It claims
> +	* Initialisation delay between VDD low->high and the moment
> +	* when the i2c command is available.
> +	* From the datasheet, it should be 10ms + 2ms (max power
> +	* up sequence duration)
>
> 10ms seems like a long time, it would be nice to have the datasheet to
> cross-check.

It does seem quite long. I couldn't find a datasheet anywhere
so the value I discovered is the best I have. I've added the
author of that patch to CC; maybe they have some info to
contribute.

> Thanks
>    j
>
> >  ---
> >  Changes since v1:
> >    - Reorganize variable declaration
> >    - Change the power-on delay range to 3000-3500 microseconds.
> >
> >   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..c2b2542a0056 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.
> >  + */
> >  +#define AK7375_POWER_DELAY_US	3000
> >
> >   #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;
> >   };
> >  @@ -133,12 +149,24 @@ static int ak7375_probe(struct i2c_client 
> > *client)
> >   {
> >   	struct ak7375_device *ak7375_dev;
> >   	int ret;
> >  +	int i;
> >
> >   	ak7375_dev = devm_kzalloc(&client->dev, sizeof(*ak7375_dev),
> >   				  GFP_KERNEL);
> >   	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 + 500);
> >  +
> >   	ret = ak7375_i2c_write(ak7375_dev, AK7375_REG_CONT,
> >   		AK7375_MODE_ACTIVE, 1);
> >   	if (ret) {
> >  --
> >  2.37.0