linux-kernel - Re: 回复: [PATCH v2 2/5] media: cadence: csi2rx: Add system PM support

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Message-ID: <416ec496-a224-47d0-b092-6976aa039318@ideasonboard.com>
Date: Mon, 22 Jul 2024 11:53:02 +0300
From: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
To: Changhuang Liang <changhuang.liang@...rfivetech.com>,
 Mauro Carvalho Chehab <mchehab@...nel.org>,
 Maxime Ripard <mripard@...nel.org>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Hans Verkuil <hverkuil-cisco@...all.nl>
Cc: Jacopo Mondi <jacopo.mondi@...asonboard.com>,
 Laurent Pinchart <laurent.pinchart@...asonboard.com>,
 Jack Zhu <jack.zhu@...rfivetech.com>,
 Keith Zhao <keith.zhao@...rfivetech.com>, Jayshri Pawar
 <jpawar@...ence.com>, Jai Luthra <j-luthra@...com>,
 "linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "linux-staging@...ts.linux.dev" <linux-staging@...ts.linux.dev>
Subject: Re: 回复: [PATCH v2 2/5] media: cadence: csi2rx: Add system PM support

Hi,

On 22/07/2024 05:17, Changhuang Liang wrote:
> Hi, Tomi
> 
>> Hi,
>>
>> On 18/07/2024 06:28, Changhuang Liang wrote:
>>> Add system PM support make it stopping streaming at system suspend
>>> time, and restarting streaming at system resume time.
>>>
>>> Signed-off-by: Changhuang Liang <changhuang.liang@...rfivetech.com>
>>> ---
>>>    drivers/media/platform/cadence/cdns-csi2rx.c | 32
>> ++++++++++++++++++++
>>>    1 file changed, 32 insertions(+)
>>>
>>> diff --git a/drivers/media/platform/cadence/cdns-csi2rx.c
>>> b/drivers/media/platform/cadence/cdns-csi2rx.c
>>> index 981819adbb3a..81e90b31e9f8 100644
>>> --- a/drivers/media/platform/cadence/cdns-csi2rx.c
>>> +++ b/drivers/media/platform/cadence/cdns-csi2rx.c
>>> @@ -776,8 +776,40 @@ static int csi2rx_runtime_resume(struct device
>> *dev)
>>>    	return ret;
>>>    }
>>>
>>> +static int __maybe_unused csi2rx_suspend(struct device *dev) {
>>> +	struct csi2rx_priv *csi2rx = dev_get_drvdata(dev);
>>> +
>>> +	mutex_lock(&csi2rx->lock);
>>> +	if (csi2rx->count)
>>> +		csi2rx_stop(csi2rx);
>>> +	mutex_unlock(&csi2rx->lock);
>>> +
>>> +	pm_runtime_force_suspend(dev);
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +static int __maybe_unused csi2rx_resume(struct device *dev) {
>>> +	struct csi2rx_priv *csi2rx = dev_get_drvdata(dev);
>>> +	int ret;
>>> +
>>> +	ret = pm_runtime_force_resume(dev);
>>> +	if (ret < 0)
>>> +		return ret;
>>> +
>>> +	mutex_lock(&csi2rx->lock);
>>> +	if (csi2rx->count)
>>> +		csi2rx_start(csi2rx);
>>> +	mutex_unlock(&csi2rx->lock);
>>> +
>>> +	return 0;
>>> +}
>>> +
>>>    static const struct dev_pm_ops csi2rx_pm_ops = {
>>>    	SET_RUNTIME_PM_OPS(csi2rx_runtime_suspend,
>> csi2rx_runtime_resume,
>>> NULL)
>>> +	SET_SYSTEM_SLEEP_PM_OPS(csi2rx_suspend, csi2rx_resume)
>>>    };
>>>
>>>    static const struct of_device_id csi2rx_of_table[] = {
>>
>> If I'm not mistaken, this is a subdev driver, and is somewhere in the middle of
>> the pipeline. Afaiu, only the driver that handles the v4l2 video devices should
>> have system suspend hooks. The job of that driver is then to disable or enable
>> the pipeline using v4l2 functions, and for the rest of the pipeline system
>> suspend looks just like a normal pipeline disable.
>>
> 
> I see that the imx219 has a commit:
> 
> commit b8074db07429b845b805416d261b502f814a80fe
> Author: Laurent Pinchart <laurent.pinchart@...asonboard.com>
> Date:   Thu Sep 14 21:16:49 2023 +0300
> 
>      media: i2c: imx219: Drop system suspend and resume handlers
> 
>      Stopping streaming on a camera pipeline at system suspend time, and
>      restarting it at system resume time, requires coordinated action between
>      the bridge driver and the camera sensor driver. This is handled by the
>      bridge driver calling the sensor's .s_stream() handler at system suspend
>      and resume time. There is thus no need for the sensor to independently
>      implement system sleep PM operations. Drop them.
> 
>      The streaming field of the driver's private structure is now unused,
>      drop it as well.
> 
>      Signed-off-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
>      Reviewed-by: Dave Stevenson <dave.stevenson@...pberrypi.com>
>      Signed-off-by: Sakari Ailus <sakari.ailus@...ux.intel.com>
>      Signed-off-by: Hans Verkuil <hverkuil-cisco@...all.nl>
> 
> Implement the system PM of sensor using bridge. This csi2rx is also a bridge.
> So I add system PM in this driver.

It is not a bridge in the sense that the commit message means. The 
system suspend should be handled in the last (or first, depending on 
which way you think about it) driver in the pipeline, the one that 
handles the VIDIOC_STREAMON.

  Tomi