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

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Message-Id: <WIK0FR.TSG3JTBEBBDN@gmail.com>
Date:   Thu, 14 Jul 2022 18:06:32 +0400
From:   Yassine Oudjana <yassine.oudjana@...il.com>
To:     Jacopo Mondi <jacopo@...ndi.org>
Cc:     Lee Jackson <info@...ucam.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Tianshu Qiu <tian.shu.qiu@...el.com>,
        Bingbu Cao <bingbu.cao@...el.com>,
        Yassine Oudjana <y.oudjana@...tonmail.com>,
        linux-media@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/3] media: i2c: ak7375: Add regulator management


On Wed, Jul 13 2022 at 09:39:51 +0200, Jacopo Mondi <jacopo@...ndi.org> 
wrote:
> Hi Yassine
> 
> On Mon, Jul 11, 2022 at 06:40:39PM +0400, Yassine Oudjana wrote:
>>  From: Yassine Oudjana <y.oudjana@...tonmail.com>
>> 
>>  Make the driver get needed regulators on probe and enable/disable
>>  them on runtime PM callbacks.
>> 
>>  Signed-off-by: Yassine Oudjana <y.oudjana@...tonmail.com>
> 
> 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
>>