Re: [PATCH] media: i2c: imx274: fix s_frame_interval runtime resume not requested

[Sakari Ailus <sakari.ailus@linux.intel.com>]

Hi Eugen,

On Wed, Nov 17, 2021 at 04:52:40PM +0000, Eugen.Hristev@microchip.com wrote:
> On 11/17/21 6:11 PM, Sakari Ailus wrote:
> > EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> > 
> > Hi Eugen,
> > 
> > On Wed, Nov 17, 2021 at 05:40:09PM +0200, Eugen Hristev wrote:
> >> pm_runtime_resume_and_get should be called when the s_frame_interval
> >> is called.
> >>
> >> The driver will try to access device registers to configure VMAX, coarse
> >> time and exposure.
> >>
> >> Currently if the runtime is not resumed, this fails:
> >>   # media-ctl -d /dev/media0 --set-v4l2 '"IMX274 1-001a":0[fmt:SRGGB10_1X10/3840x2
> >> 160@1/10]'
> >>
> >> IMX274 1-001a: imx274_binning_goodness: ask 3840x2160, size 3840x2160, goodness 0
> >> IMX274 1-001a: imx274_binning_goodness: ask 3840x2160, size 1920x1080, goodness -3000
> >> IMX274 1-001a: imx274_binning_goodness: ask 3840x2160, size 1280x720, goodness -4000
> >> IMX274 1-001a: imx274_binning_goodness: ask 3840x2160, size 1280x540, goodness -4180
> >> IMX274 1-001a: __imx274_change_compose: selected 1x1 binning
> >> IMX274 1-001a: imx274_set_frame_interval: input frame interval = 1 / 10
> >> IMX274 1-001a: imx274_read_mbreg : addr 0x300e, val=0x1 (2 bytes)
> >> IMX274 1-001a: imx274_set_frame_interval : register SVR = 1
> >> IMX274 1-001a: imx274_read_mbreg : addr 0x30f6, val=0x6a8 (2 bytes)
> >> IMX274 1-001a: imx274_set_frame_interval : register HMAX = 1704
> >> IMX274 1-001a: imx274_set_frame_length : input length = 2112
> >> IMX274 1-001a: imx274_write_mbreg : i2c bulk write failed, 30f8 = 884 (3 bytes)
> >> IMX274 1-001a: imx274_set_frame_length error = -121
> >> IMX274 1-001a: imx274_set_frame_interval error = -121
> >> Unable to setup formats: Remote I/O error (121)
> >>
> >> The device is not resumed thus the remote I/O error.
> >>
> >> Setting the frame interval works at streaming time, because
> >> pm_runtime_resume_and_get is called at s_stream time before sensor setup.
> >> The failure happens when only the s_frame_interval is called separately
> >> independently on streaming time.
> >>
> >> Fixes: ad97bc37426c ("media: i2c: imx274: Add IMX274 power on and off sequence"
> >> Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
> >> ---
> >>   drivers/media/i2c/imx274.c | 5 +++++
> >>   1 file changed, 5 insertions(+)
> >>
> >> diff --git a/drivers/media/i2c/imx274.c b/drivers/media/i2c/imx274.c
> >> index e89ef35a71c5..6e63fdcc5e46 100644
> >> --- a/drivers/media/i2c/imx274.c
> >> +++ b/drivers/media/i2c/imx274.c
> >> @@ -1420,6 +1420,10 @@ static int imx274_s_frame_interval(struct v4l2_subdev *sd,
> >>        int min, max, def;
> >>        int ret;
> >>
> >> +     ret = pm_runtime_resume_and_get(&imx274->client->dev);
> >> +     if (ret < 0)
> >> +             return ret;
> >> +
> >>        mutex_lock(&imx274->lock);
> >>        ret = imx274_set_frame_interval(imx274, fi->interval);
> >>
> >> @@ -1451,6 +1455,7 @@ static int imx274_s_frame_interval(struct v4l2_subdev *sd,
> >>
> >>   unlock:
> >>        mutex_unlock(&imx274->lock);
> >> +     pm_runtime_put(&imx274->client->dev);
> >>
> >>        return ret;
> >>   }
> > 
> > If the device is powered off in the end, could you instead not power it on
> > in the first place? I.e. see how this works for the s_ctrl() callback.
> 
> 
> Hi Sakari,
> 
> I tried this initially, as in s_ctrl,
> 
>          if (!pm_runtime_get_if_in_use(&imx274->client->dev)) 
> 
>                  return 0;
> 
> 
> However, if the device is powered off, the s_frame_interval does not do 
> anything (return 0), and the frame interval is not changed. Not even the 
> internal structure frame_interval is updated (as this is updated after 
> configuring the actual device).
> And in consequence media-ctl -p will still print the old frame interval.
> 
> So either we power on the device to set everything, or, things have to 
> be set in the software struct and written once streaming starts.
> I am in favor of the first option (hence the patch), to avoid having 
> configuration that was requested but not written to the device itself.
> The second option would require some rework to move the software part 
> before the hardware part, and to assume that the hardware part never 
> fails in bounds or by other reason (or the software part would be no 
> longer consistent)
> 
> What do you think ?

Seems reasonable, but the driver is hardly doing this in an exemplary way.
Still the rework might not worth the small gain. I'll take this one then.

-- 
Kind regards,

Sakari Ailus