linux-kernel - Re: [PATCH] venus: vdec: fix decoded data size

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Date:   Wed, 19 Sep 2018 18:02:58 +0300
From:   Stanimir Varbanov <stanimir.varbanov@...aro.org>
To:     Alexandre Courbot <acourbot@...omium.org>,
        Hans Verkuil <hverkuil@...all.nl>
Cc:     Nicolas Dufresne <nicolas@...fresne.ca>, vgarodia@...eaurora.org,
        Linux Media Mailing List <linux-media@...r.kernel.org>,
        linux-arm-msm@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] venus: vdec: fix decoded data size

Hi Alex,

On 09/19/2018 01:32 PM, Alexandre Courbot wrote:
> On Mon, Sep 17, 2018 at 11:33 PM Hans Verkuil <hverkuil@...all.nl> wrote:
>>
>> On 09/17/2018 04:30 PM, Stanimir Varbanov wrote:
>>> Hi Hans,
>>>
>>> On 09/17/2018 01:00 PM, Hans Verkuil wrote:
>>>> On 07/18/2018 04:37 PM, Stanimir Varbanov wrote:
>>>>> Hi,
>>>>>
>>>>> On 07/18/2018 04:26 PM, Nicolas Dufresne wrote:
>>>>>> Le mercredi 18 juillet 2018 à 14:31 +0300, Stanimir Varbanov a écrit :
>>>>>>> Hi Vikash,
>>>>>>>
>>>>>>> On 07/02/2018 10:44 AM, Vikash Garodia wrote:
>>>>>>>> Exisiting code returns the max of the decoded
>>>>>>>> size and buffer size. It turns out that buffer
>>>>>>>> size is always greater due to hardware alignment
>>>>>>>> requirement. As a result, payload size given to
>>>>>>>> client is incorrect. This change ensures that
>>>>>>>> the bytesused is assigned to actual payload size.
>>>>>>>>
>>>>>>>> Change-Id: Ie6f3429c0cb23f682544748d181fa4fa63ca2e28
>>>>>>>> Signed-off-by: Vikash Garodia <vgarodia@...eaurora.org>
>>>>>>>> ---
>>>>>>>>  drivers/media/platform/qcom/venus/vdec.c | 2 +-
>>>>>>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>>>>>>
>>>>>>>> diff --git a/drivers/media/platform/qcom/venus/vdec.c
>>>>>>>> b/drivers/media/platform/qcom/venus/vdec.c
>>>>>>>> index d079aeb..ada1d2f 100644
>>>>>>>> --- a/drivers/media/platform/qcom/venus/vdec.c
>>>>>>>> +++ b/drivers/media/platform/qcom/venus/vdec.c
>>>>>>>> @@ -890,7 +890,7 @@ static void vdec_buf_done(struct venus_inst
>>>>>>>> *inst, unsigned int buf_type,
>>>>>>>>
>>>>>>>>                  vb = &vbuf->vb2_buf;
>>>>>>>>                  vb->planes[0].bytesused =
>>>>>>>> -                        max_t(unsigned int, opb_sz, bytesused);
>>>>>>>> +                        min_t(unsigned int, opb_sz, bytesused);
>>>>>>>
>>>>>>> Most probably my intension was to avoid bytesused == 0, but that is
>>>>>>> allowed from v4l2 driver -> userspace direction
>>>>>>
>>>>>> It remains bad practice since it was used by decoders to indicate the
>>>>>> last buffer. Some userspace (some GStreamer versions) will stop working
>>>>>> if you start returning 0.
>>>>>
>>>>> I think it is legal v4l2 driver to return bytesused = 0 when userspace
>>>>> issues streamoff on both queues before EOS, no? Simply because the
>>>>> capture buffers are empty.
>>>>>
>>>>
>>>> Going through some of the older pending patches I found this one:
>>>>
>>>> So is this patch right or wrong?
>>>
>>> I'm not sure either, let's not applying it for now (if Nicolas is right
>>> this will break gstreamer plugin).
>>>
>>
>> OK, I marked this as Rejected. If you change your mind it can be reposted :-)
> 
> Mmm I'm not saying it has to be done in the current form, but at the
> moment the returned bytesused seems to be wrong (at least Chrome is
> not happy). We are returning the total size of the buffer instead of
> the actually useful payload.
> 
> If the intent is to avoid returning bytesused == 0 except for the
> special case of the last buffer, how about the following?
> 
> --- a/drivers/media/platform/qcom/venus/vdec.c
> +++ b/drivers/media/platform/qcom/venus/vdec.c
> @@ -943,8 +943,7 @@ static void vdec_buf_done(struct venus_inst *inst,
> unsigned int buf_type,
>                unsigned int opb_sz = venus_helper_get_opb_size(inst);
> 
>                vb = &vbuf->vb2_buf;
> -               vb->planes[0].bytesused =
> -                       max_t(unsigned int, opb_sz, bytesused);
> +                vb2_set_plane_payload(vb, 0, bytesused ? : opb_sz);
>                vb->planes[0].data_offset = data_offset;
>                vb->timestamp = timestamp_us * NSEC_PER_USEC;
>                vbuf->sequence = inst->sequence_cap++;
> 
> It works fine for me, and should not return 0 more often than it did
> before (i.e. never). In practice I also never see the firmware
> reporting a payload of zero on SDM845, but maybe older chips differ?

yes, it looks fine. Let me test it with older versions.

-- 
regards,
Stan