linux-kernel - Re: [PATCH v2 09/20] media: i2c: ov4689: Use runtime PM autosuspend

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Message-ID: <ZdpFwtU0iJEFWxhu@kekkonen.localdomain>
Date: Sat, 24 Feb 2024 19:38:42 +0000
From: Sakari Ailus <sakari.ailus@...ux.intel.com>
To: Mikhail Rudenko <mike.rudenko@...il.com>
Cc: Sakari Ailus <sakari.ailus@....fi>, linux-media@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	Jacopo Mondi <jacopo@...ndi.org>,
	Tommaso Merciai <tomm.merciai@...il.com>,
	Christophe JAILLET <christophe.jaillet@...adoo.fr>,
	Dave Stevenson <dave.stevenson@...pberrypi.com>,
	Mauro Carvalho Chehab <mchehab@...nel.org>
Subject: Re: [PATCH v2 09/20] media: i2c: ov4689: Use runtime PM autosuspend

Hi Mikhail,

On Fri, Feb 23, 2024 at 06:18:12PM +0300, Mikhail Rudenko wrote:
> 
> Hi Sakari,
> 
> and thanks for the review!
> 
> On 2024-02-23 at 08:19 GMT, Sakari Ailus <sakari.ailus@...ux.intel.com> wrote:
> 
> > Hi Mikhail,
> >
> > On Mon, Jan 08, 2024 at 06:06:52PM +0300, Mikhail Rudenko wrote:
> >> Hi Sakari,
> >>
> >> Thanks for the review!
> >>
> >> On 2024-01-08 at 11:18 GMT, Sakari Ailus <sakari.ailus@....fi> wrote:
> >>
> >> > Hi Mikhail,
> >> >
> >> > On Mon, Dec 18, 2023 at 08:40:30PM +0300, Mikhail Rudenko wrote:
> >> >> Use runtime PM autosuspend to avoid powering off the sensor during
> >> >> fast stop-reconfigure-restart cycles.
> >> >>
> >> >> Signed-off-by: Mikhail Rudenko <mike.rudenko@...il.com>
> >> >> ---
> >> >>  drivers/media/i2c/ov4689.c | 22 +++++++++++++++-------
> >> >>  1 file changed, 15 insertions(+), 7 deletions(-)
> >> >>
> >> >> diff --git a/drivers/media/i2c/ov4689.c b/drivers/media/i2c/ov4689.c
> >> >> index 5300e621ff90..64cc6d9e48cc 100644
> >> >> --- a/drivers/media/i2c/ov4689.c
> >> >> +++ b/drivers/media/i2c/ov4689.c
> >> >> @@ -407,26 +407,27 @@ static int ov4689_s_stream(struct v4l2_subdev *sd, int on)
> >> >>  					  ov4689->cur_mode->num_regs,
> >> >>  					  NULL);
> >> >>  		if (ret) {
> >> >> -			pm_runtime_put(dev);
> >> >> +			pm_runtime_put_sync(dev);
> >> >
> >> > Why are you switching to pm_runtime_put_sync() here? That isn't covered by
> >> > the commit message (nor I think should be done).
> >>
> >> PM autosuspend conversion was suggested earlier by Laurent in his review
> >> of this series [1], and he adviced looking at how it was done for the
> >> imx290 driver. I followed along the lines of the corresponding patch
> >> [2].
> >
> > There's no need to use the _sync() variant here. And at least it wouldn't
> > be related to autosuspend, were you to switch to that.
> 
> Ok, will use pm_runtime_put in v3. Or do you suggest dropping this patch
> altogether? Laurent?

Using autosuspend is preferred.

Much of the benefit come from avoiding redundant register writes but that's
a separate matter.

> 
> >>
> >> >>  			goto unlock_and_return;
> >> >>  		}
> >> >>
> >> >>  		ret = __v4l2_ctrl_handler_setup(&ov4689->ctrl_handler);
> >> >>  		if (ret) {
> >> >> -			pm_runtime_put(dev);
> >> >> +			pm_runtime_put_sync(dev);
> >> >>  			goto unlock_and_return;
> >> >>  		}
> >> >>
> >> >>  		ret = cci_write(ov4689->regmap, OV4689_REG_CTRL_MODE,
> >> >>  				OV4689_MODE_STREAMING, NULL);
> >> >>  		if (ret) {
> >> >> -			pm_runtime_put(dev);
> >> >> +			pm_runtime_put_sync(dev);
> >> >>  			goto unlock_and_return;
> >> >>  		}
> >> >>  	} else {
> >> >>  		cci_write(ov4689->regmap, OV4689_REG_CTRL_MODE,
> >> >>  			  OV4689_MODE_SW_STANDBY, NULL);
> >> >> -		pm_runtime_put(dev);
> >> >> +		pm_runtime_mark_last_busy(dev);
> >> >> +		pm_runtime_put_autosuspend(dev);
> >> >>  	}
> >> >>
> >> >>  unlock_and_return:
> >> >> @@ -606,7 +607,9 @@ static int ov4689_set_ctrl(struct v4l2_ctrl *ctrl)
> >> >>  		break;
> >> >>  	}
> >> >>
> >> >> -	pm_runtime_put(dev);
> >> >> +	pm_runtime_mark_last_busy(dev);
> >> >> +	pm_runtime_put_autosuspend(dev);
> >> >
> >> > Also note that with runtime PM autosuspend,  you have to use
> >> > pm_runtime_get_if_active() instead of pm_runtime_get_if_in_use().
> >>
> >> Noted, will do so in v3.
> >>
> >> >> +
> >> >>  	return ret;
> >> >>  }
> >> >>
> >> >> @@ -877,8 +880,10 @@ static int ov4689_probe(struct i2c_client *client)
> >> >>  	}
> >> >>
> >> >>  	pm_runtime_set_active(dev);
> >> >> +	pm_runtime_get_noresume(dev);
> >> >>  	pm_runtime_enable(dev);
> >> >> -	pm_runtime_idle(dev);
> >> >> +	pm_runtime_set_autosuspend_delay(dev, 1000);
> >> >> +	pm_runtime_use_autosuspend(dev);
> >> >>
> >> >>  	ret = v4l2_async_register_subdev_sensor(sd);
> >> >>  	if (ret) {
> >> >> @@ -886,11 +891,14 @@ static int ov4689_probe(struct i2c_client *client)
> >> >>  		goto err_clean_subdev_pm;
> >> >>  	}
> >> >>
> >> >> +	pm_runtime_mark_last_busy(dev);
> >> >> +	pm_runtime_put_autosuspend(dev);
> >> >> +
> >> >>  	return 0;
> >> >>
> >> >>  err_clean_subdev_pm:
> >> >>  	pm_runtime_disable(dev);
> >> >> -	pm_runtime_set_suspended(dev);
> >> >> +	pm_runtime_put_noidle(dev);
> >> >>  	v4l2_subdev_cleanup(sd);
> >> >>  err_clean_entity:
> >> >>  	media_entity_cleanup(&sd->entity);
> >>
> >> [1] https://lore.kernel.org/all/20231211181935.GG27535@pendragon.ideasonboard.com/
> >> [2] https://lore.kernel.org/all/20230116144454.1012-14-laurent.pinchart@ideasonboard.com/
> >>
> 
> 

-- 
Kind regards,

Sakari Ailus