linux-kernel - Re: [PATCH] media: dw9714: add support for powerdown pin

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <f4ebc809-f30e-46aa-9f36-db98370ebe6e@emfend.at>
Date: Wed, 11 Jun 2025 14:15:10 +0200
From: Matthias Fend <matthias.fend@...end.at>
To: Sakari Ailus <sakari.ailus@...ux.intel.com>
Cc: Mauro Carvalho Chehab <mchehab@...nel.org>, linux-media@...r.kernel.org,
 linux-kernel@...r.kernel.org, bsp-development.geo@...ca-geosystems.com
Subject: Re: [PATCH] media: dw9714: add support for powerdown pin

Hi Sakari,

thanks for your comments.

Am 11.06.2025 um 11:33 schrieb Sakari Ailus:
> Hi Matthias,
> 
> Thanks for the patch.
> 
> On Wed, Jun 11, 2025 at 09:13:33AM +0200, Matthias Fend wrote:
>> Add support for the powerdown pin (xSD), which can be used to put the VCM
>> driver into power down mode. This is useful, for example, if the VCM
>> driver's power supply cannot be controlled.
>> The use of the powerdown pin is optional.
> 
> Please rewrap. Most editors can do it for you.

To me the message body looks line wrapped at 75 columns. The last 
sentence on a new line. At least that is what was intended.
So I think I'm missing something here. Can you please tell me what 
exactly I should change?

> 
>>
>> Signed-off-by: Matthias Fend <matthias.fend@...end.at>
>> ---
>>   drivers/media/i2c/Kconfig  |  2 +-
>>   drivers/media/i2c/dw9714.c | 16 ++++++++++++++++
>>   2 files changed, 17 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/media/i2c/Kconfig b/drivers/media/i2c/Kconfig
>> index e45ba127069fc0848f1a06ceb789efd3c222c008..e923daeec9c574c5b8c7014b9e83fcbad47866c0 100644
>> --- a/drivers/media/i2c/Kconfig
>> +++ b/drivers/media/i2c/Kconfig
>> @@ -748,7 +748,7 @@ config VIDEO_AK7375
>>   
>>   config VIDEO_DW9714
>>   	tristate "DW9714 lens voice coil support"
>> -	depends on I2C && VIDEO_DEV
>> +	depends on GPIOLIB && I2C && VIDEO_DEV
>>   	select MEDIA_CONTROLLER
>>   	select VIDEO_V4L2_SUBDEV_API
>>   	select V4L2_ASYNC
>> diff --git a/drivers/media/i2c/dw9714.c b/drivers/media/i2c/dw9714.c
>> index 2ddd7daa79e28a2cde915b4173fa27e60d5a2b57..5b78c1848f80bc3e32df13d149f3865ff8defe6e 100644
>> --- a/drivers/media/i2c/dw9714.c
>> +++ b/drivers/media/i2c/dw9714.c
>> @@ -2,6 +2,7 @@
>>   // Copyright (c) 2015--2017 Intel Corporation.
>>   
>>   #include <linux/delay.h>
>> +#include <linux/gpio/consumer.h>
>>   #include <linux/i2c.h>
>>   #include <linux/module.h>
>>   #include <linux/pm_runtime.h>
>> @@ -38,6 +39,7 @@ struct dw9714_device {
>>   	struct v4l2_subdev sd;
>>   	u16 current_val;
>>   	struct regulator *vcc;
>> +	struct gpio_desc *powerdown_gpio;
>>   };
>>   
>>   static inline struct dw9714_device *to_dw9714_vcm(struct v4l2_ctrl *ctrl)
>> @@ -151,11 +153,20 @@ static int dw9714_probe(struct i2c_client *client)
>>   	if (IS_ERR(dw9714_dev->vcc))
>>   		return PTR_ERR(dw9714_dev->vcc);
>>   
>> +	dw9714_dev->powerdown_gpio = devm_gpiod_get_optional(&client->dev,
>> +							     "powerdown",
>> +							     GPIOD_OUT_LOW);
>> +	if (IS_ERR(dw9714_dev->powerdown_gpio))
>> +		return dev_err_probe(&client->dev,
>> +				     PTR_ERR(dw9714_dev->powerdown_gpio),
>> +				     "could not get powerdown gpio\n");
>> +
>>   	rval = regulator_enable(dw9714_dev->vcc);
>>   	if (rval < 0) {
>>   		dev_err(&client->dev, "failed to enable vcc: %d\n", rval);
>>   		return rval;
>>   	}
>> +	gpiod_set_value_cansleep(dw9714_dev->powerdown_gpio, 0);
> 
> This seems to be redundant, you're already setting the GPIO low when
> acquiring it. Typically the order is different, though: the regulator is
> enabled first. Also related to the following comment.

Yes, that's right. I'll set the pin during initialization so that 
power-down mode is active. So at least the sequence is always the same.

> 
>>   
>>   	usleep_range(1000, 2000);
>>   
>> @@ -185,6 +196,7 @@ static int dw9714_probe(struct i2c_client *client)
>>   	return 0;
>>   
>>   err_cleanup:
>> +	gpiod_set_value_cansleep(dw9714_dev->powerdown_gpio, 1);
>>   	regulator_disable(dw9714_dev->vcc);
> 
> It'd be nice to have a single implementation of the power-on and power-off
> sequences. Now there are two.

Okay, will do so.

Thanks,
  ~Matthias

> 
>>   	v4l2_ctrl_handler_free(&dw9714_dev->ctrls_vcm);
>>   	media_entity_cleanup(&dw9714_dev->sd.entity);
>> @@ -200,6 +212,7 @@ static void dw9714_remove(struct i2c_client *client)
>>   
>>   	pm_runtime_disable(&client->dev);
>>   	if (!pm_runtime_status_suspended(&client->dev)) {
>> +		gpiod_set_value_cansleep(dw9714_dev->powerdown_gpio, 1);
>>   		ret = regulator_disable(dw9714_dev->vcc);
>>   		if (ret) {
>>   			dev_err(&client->dev,
>> @@ -234,6 +247,7 @@ static int __maybe_unused dw9714_vcm_suspend(struct device *dev)
>>   		usleep_range(DW9714_CTRL_DELAY_US, DW9714_CTRL_DELAY_US + 10);
>>   	}
>>   
>> +	gpiod_set_value_cansleep(dw9714_dev->powerdown_gpio, 1);
>>   	ret = regulator_disable(dw9714_dev->vcc);
>>   	if (ret)
>>   		dev_err(dev, "Failed to disable vcc: %d\n", ret);
>> @@ -262,6 +276,8 @@ static int  __maybe_unused dw9714_vcm_resume(struct device *dev)
>>   		dev_err(dev, "Failed to enable vcc: %d\n", ret);
>>   		return ret;
>>   	}
>> +	gpiod_set_value_cansleep(dw9714_dev->powerdown_gpio, 0);
>> +
>>   	usleep_range(1000, 2000);
>>   
>>   	for (val = dw9714_dev->current_val % DW9714_CTRL_STEPS;
>>
>