linux-kernel - Re: [PATCH] media: i2c: improve suspend/resume switch performance for GT9769 VCM driver

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Message-ID: <CAC=S1nh76iKhMV4roBe4mLTrq-eHqz-3-fYWzNcWAETvj-JETA@mail.gmail.com>
Date: Mon, 23 Sep 2024 17:07:40 +0800
From: Fei Shao <fshao@...omium.org>
To: Zhi Mao <zhi.mao@...iatek.com>
Cc: Sakari Ailus <sakari.ailus@...ux.intel.com>, 
	Mauro Carvalho Chehab <mchehab@...nel.org>, Matthias Brugger <matthias.bgg@...il.com>, 
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>, linux-media@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
	linux-mediatek@...ts.infradead.org, shengnan.wang@...iatek.com, 
	yaya.chang@...iatek.com, teddy.chen@...iatek.com, yunkec@...omium.org, 
	10572168@...com, ot_xiaofeiw.wang@...iatek.com
Subject: Re: [PATCH] media: i2c: improve suspend/resume switch performance for
 GT9769 VCM driver

Hi Zhi,

On Sat, Aug 31, 2024 at 1:54 PM Zhi Mao <zhi.mao@...iatek.com> wrote:

Suggestion for the new patch title:
  media: i2c: dw9768: Use runtime PM autosuspend

to better describe "what" this patch does to the DW9768 driver, not "why".
Also there's nothing to do with GT9769 in this patch.

>
> Chromebook camera AP can switch between video and photo mode,
> the behavior corresponding to VCM is suspend and resume,
> it will cause camera preview is not smooth during switching operation.
> We use autosuspend function can fix this issue.
>
> Signed-off-by: Zhi Mao <zhi.mao@...iatek.com>
> ---
>  drivers/media/i2c/dw9768.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/media/i2c/dw9768.c b/drivers/media/i2c/dw9768.c
> index 18ef2b35c9aa..7449d29df901 100644
> --- a/drivers/media/i2c/dw9768.c
> +++ b/drivers/media/i2c/dw9768.c
> @@ -374,7 +374,7 @@ static int dw9768_open(struct v4l2_subdev *sd, struct v4l2_subdev_fh *fh)
>
>  static int dw9768_close(struct v4l2_subdev *sd, struct v4l2_subdev_fh *fh)
>  {
> -       pm_runtime_put(sd->dev);

Call pm_runtime_mark_last_busy() to update the power.last_busy field
for autosuspend to work properly.

> +       pm_runtime_put_sync_autosuspend(sd->dev);

Use pm_runtime_put_autosuspend().
Don't switch to the synchronized variant without reasons.

>
>         return 0;
>  }
> @@ -490,6 +490,7 @@ static int dw9768_probe(struct i2c_client *client)
>                 goto err_power_off;
>         }
>
> +       pm_runtime_use_autosuspend(dev);

Add pm_runtime_set_autosuspend_delay() before calling
pm_runtime_use_autosuspend() to avoid rapid power state bouncing.

Regards,
Fei



>         pm_runtime_idle(dev);
>
>         return 0;
> --
> 2.46.0
>
>