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Subject: Re: [RFC PATCH v11 6/9] media: tegra: Add Tegra210 Video input driver
From:   Sowjanya Komatineni <skomatineni@nvidia.com>
To:     Dmitry Osipenko <digetx@gmail.com>, <thierry.reding@gmail.com>,
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On 4/30/20 10:06 AM, Sowjanya Komatineni wrote:
>
> On 4/30/20 9:29 AM, Sowjanya Komatineni wrote:
>>
>> On 4/30/20 9:04 AM, Sowjanya Komatineni wrote:
>>>
>>> On 4/30/20 7:13 AM, Dmitry Osipenko wrote:
>>>> 30.04.2020 17:02, Dmitry Osipenko =D0=BF=D0=B8=D1=88=D0=B5=D1=82:
>>>>> 30.04.2020 16:56, Dmitry Osipenko =D0=BF=D0=B8=D1=88=D0=B5=D1=82:
>>>>>> 30.04.2020 01:00, Sowjanya Komatineni =D0=BF=D0=B8=D1=88=D0=B5=D1=82=
:
>>>>>>> +static int chan_capture_kthread_finish(void *data)
>>>>>>> +{
>>>>>>> +=C2=A0=C2=A0=C2=A0 struct tegra_vi_channel *chan =3D data;
>>>>>>> +=C2=A0=C2=A0=C2=A0 struct tegra_channel_buffer *buf;
>>>>>>> +
>>>>>>> +=C2=A0=C2=A0=C2=A0 set_freezable();
>>>>>>> +
>>>>>>> +=C2=A0=C2=A0=C2=A0 while (1) {
>>>>>>> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 try_to_freeze();
>>>>>> I guess it won't be great to freeze in the middle of a capture=20
>>>>>> process, so:
>>>>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 if (list_empty(&chan->don=
e))
>>>>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 t=
ry_to_freeze();
>>>>> And here should be some locking protection in order not race with the
>>>>> chan_capture_kthread_start because kthread_finish could freeze before
>>>>> kthread_start.
>>>> Or maybe both start / finish threads should simply be allowed to=20
>>>> freeze
>>>> only when both capture and done lists are empty.
>>>>
>>>> if (list_empty(&chan->capture) &&
>>>> =C2=A0=C2=A0=C2=A0=C2=A0 list_empty(&chan->done))
>>>> =C2=A0=C2=A0=C2=A0=C2=A0try_to_freeze();
>>>
>>> good to freeze when not in middle of the frame capture but why=20
>>> should we not allow freeze in between captures?
>>>
>>> Other drivers do allow freeze in between frame captures.
>>>
>>> I guess we can freeze before dequeue for capture and in finish=20
>>> thread we can freeze after capture done. This also don't need to=20
>>> check for list_empty with freeze to allow between frame captures.
>>>
>> Also if we add check for both lists empty, freeze is not allowed as=20
>> long as streaming is going on and in case of continuous streaming=20
>> freeze will never happen.
>
To allow freeze b/w frames (but not in middle of a frame),

for capture_start thread, probably we can do unconditional try_to_freeze()

for capture_finish thread, at end of capture done we can do=20
try_to_freeze() only when done list is empty

> Hi Dmitry,
>
> Will update in v12 to not allow freeze in middle of a frame capture.
>
> Can you please confirm on above if you agree to allow freeze to happen=20
> in b/w frame captures?
>
> Also as most feedback has been received from you by now, appreciate if=20
> you can provide all in this v11 if you have anything else so we will=20
> not have any new changes after v12.
>
> Thanks
>
> Sowjanya
>