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

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Message-ID: <772469b0-c279-6762-091d-821c58717941@wanadoo.fr>
Date:   Wed, 20 Jul 2022 09:36:21 +0200
From:   Christophe JAILLET <christophe.jaillet@...adoo.fr>
To:     Jacopo Mondi <jacopo@...ndi.org>,
        Yassine Oudjana <yassine.oudjana@...il.com>
Cc:     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

Le 11/07/2022 à 19:31, Jacopo Mondi a écrit :
> 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>
>> ---
>> 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));
> 
> Why are you using %pe here ? Your return value is not a pointer
> (Also, missing \n at the end of the string)
> 
>  From Documentation/core-api/printk-formats.rst:
> 	%pe	-ENOSPC
> 
> For printing error pointers (i.e. a pointer for which IS_ERR() is true)
> as a symbolic error name. Error values for which no symbolic name is
> known are printed in decimal, while a non-ERR_PTR passed as the
> argument to %pe gets treated as ordinary %p.
> 

Nit: using:
+		return dev_err_probe(&client->dev, ret, "Failed to get regulators);

would be even simpler.

CJ


>> +		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
>>
>