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

[<Eugen.Hristev@microchip.com>]

On 11/17/21 11:03 PM, Sakari Ailus wrote:
> 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.


Okay, thank you.
I noticed that the fixes tag in the commit message misses the last 
closing bracket ')' . Might break automated checkers and shout out a 
warning. Maybe it's possible to amend it ?

Thanks again,
Eugen

> 
> --
> Kind regards,
> 
> Sakari Ailus
>