linux-kernel - Re: [PATCH v2] media: i2c: dw9714: add optional regulator support

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Date:   Fri, 26 Nov 2021 12:44:45 +0200
From:   Sakari Ailus <sakari.ailus@...ux.intel.com>
To:     Martin Kepplinger <martin.kepplinger@...i.sm>
Cc:     mchehab@...nel.org, broonie@...nel.org, kernel@...i.sm,
        linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
        linux-pm@...r.kernel.org, Angus Ainslie <angus@...ea.ca>
Subject: Re: [PATCH v2] media: i2c: dw9714: add optional regulator support

Hi Martin,

On Fri, Nov 26, 2021 at 10:01:07AM +0100, Martin Kepplinger wrote:
> From: Angus Ainslie <angus@...ea.ca>
> 
> Allow the dw9714 to control a regulator and adjust suspend() and resume()
> to support both runtime and system pm.
> 
> Signed-off-by: Angus Ainslie <angus@...ea.ca>
> Signed-off-by: Martin Kepplinger <martin.kepplinger@...i.sm>
> ---
> 
> revision history
> ----------------
> 
> v2: (thank you Mark)
>  * simplify the regulator_get_optional() error path
>  * fix regulator usage during probe()
> 
> v1:
> https://lore.kernel.org/linux-media/20211125080922.978583-1-martin.kepplinger@puri.sm/
> 
> 
> 
>  drivers/media/i2c/dw9714.c | 39 ++++++++++++++++++++++++++++++++++++++
>  1 file changed, 39 insertions(+)
> 
> diff --git a/drivers/media/i2c/dw9714.c b/drivers/media/i2c/dw9714.c
> index 3863dfeb8293..e8cc19b89861 100644
> --- a/drivers/media/i2c/dw9714.c
> +++ b/drivers/media/i2c/dw9714.c
> @@ -5,6 +5,7 @@
>  #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>
>  #include <media/v4l2-event.h>
> @@ -36,6 +37,7 @@ struct dw9714_device {
>  	struct v4l2_ctrl_handler ctrls_vcm;
>  	struct v4l2_subdev sd;
>  	u16 current_val;
> +	struct regulator *vcc;
>  };
>  
>  static inline struct dw9714_device *to_dw9714_vcm(struct v4l2_ctrl *ctrl)
> @@ -145,6 +147,21 @@ static int dw9714_probe(struct i2c_client *client)
>  	if (dw9714_dev == NULL)
>  		return -ENOMEM;
>  
> +	dw9714_dev->vcc = devm_regulator_get_optional(&client->dev, "vcc");

You you used regular devm_regulator_get(), you could remove the error
handling below. If there's no regulator, you'll simply get a dummy one.

> +	if (IS_ERR(dw9714_dev->vcc)) {
> +		dev_dbg(&client->dev, "No vcc regulator found: %ld\n",
> +			PTR_ERR(dw9714_dev->vcc));
> +		dw9714_dev->vcc = NULL;
> +	}
> +
> +	if (dw9714_dev->vcc) {

With (dummy) regulators, these checks become unnecessary.

> +		rval = regulator_enable(dw9714_dev->vcc);
> +		if (rval < 0) {
> +			dev_err(&client->dev, "failed to enable vcc: %d\n", rval);
> +			return rval;
> +		}
> +	}
> +
>  	v4l2_i2c_subdev_init(&dw9714_dev->sd, client, &dw9714_ops);
>  	dw9714_dev->sd.flags |= V4L2_SUBDEV_FL_HAS_DEVNODE |
>  				V4L2_SUBDEV_FL_HAS_EVENTS;
> @@ -200,6 +217,9 @@ static int __maybe_unused dw9714_vcm_suspend(struct device *dev)
>  	struct dw9714_device *dw9714_dev = sd_to_dw9714_vcm(sd);
>  	int ret, val;
>  
> +	if (pm_runtime_suspended(&client->dev))
> +		return 0;

This can't take place in a runtime PM suspend callback. You'll need to add
system suspend callback for this.

> +
>  	for (val = dw9714_dev->current_val & ~(DW9714_CTRL_STEPS - 1);
>  	     val >= 0; val -= DW9714_CTRL_STEPS) {
>  		ret = dw9714_i2c_write(client,
> @@ -208,6 +228,13 @@ static int __maybe_unused dw9714_vcm_suspend(struct device *dev)
>  			dev_err_once(dev, "%s I2C failure: %d", __func__, ret);
>  		usleep_range(DW9714_CTRL_DELAY_US, DW9714_CTRL_DELAY_US + 10);
>  	}
> +
> +	if (dw9714_dev->vcc) {
> +		ret = regulator_disable(dw9714_dev->vcc);
> +		if (ret)
> +			dev_err(dev, "Failed to disable vcc: %d\n", ret);
> +	}
> +
>  	return 0;
>  }
>  
> @@ -224,6 +251,18 @@ static int  __maybe_unused dw9714_vcm_resume(struct device *dev)
>  	struct dw9714_device *dw9714_dev = sd_to_dw9714_vcm(sd);
>  	int ret, val;
>  
> +	if (pm_runtime_suspended(&client->dev))

Same for this one.

> +		return 0;
> +
> +	if (dw9714_dev->vcc) {
> +		ret = regulator_enable(dw9714_dev->vcc);
> +		if (ret) {
> +			dev_err(dev, "Failed to enable vcc: %d\n", ret);
> +			return ret;
> +		}
> +		usleep_range(1000, 2000);
> +	}
> +
>  	for (val = dw9714_dev->current_val % DW9714_CTRL_STEPS;
>  	     val < dw9714_dev->current_val + DW9714_CTRL_STEPS - 1;
>  	     val += DW9714_CTRL_STEPS) {

-- 
Kind regards,

Sakari Ailus