linux-kernel - Re: [PATCH] media: hantro: Hook up RK3399 JPEG encoder output

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Date:   Thu, 25 Nov 2021 09:44:45 +0100
From:   Hans Verkuil <hverkuil@...all.nl>
To:     Nicolas Dufresne <nicolas@...fresne.ca>,
        Chen-Yu Tsai <wenst@...omium.org>
Cc:     Ezequiel Garcia <ezequiel@...guardiasur.com.ar>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-media@...r.kernel.org, linux-rockchip@...ts.infradead.org,
        linux-staging@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] media: hantro: Hook up RK3399 JPEG encoder output

On 23/11/2021 20:39, Nicolas Dufresne wrote:
> Le lundi 22 novembre 2021 à 11:57 +0800, Chen-Yu Tsai a écrit :
>> On Sat, Nov 20, 2021 at 12:00 AM Nicolas Dufresne <nicolas@...fresne.ca> wrote:
>>>
>>> Le vendredi 19 novembre 2021 à 15:46 +0800, Chen-Yu Tsai a écrit :
>>>> The JPEG encoder found in the Hantro H1 encoder block only produces a
>>>> raw entropy-encoded scan. The driver is responsible for building a JPEG
>>>> compliant bitstream and placing the entropy-encoded scan in it. Right
>>>> now the driver uses a bounce buffer for the hardware to output the raw
>>>> scan to.
>>>>
>>>> In commit e765dba11ec2 ("hantro: Move hantro_enc_buf_finish to JPEG
>>>> codec_ops.done"), the code that copies the raw scan from the bounce
>>>> buffer to the capture buffer was moved, but was only hooked up for the
>>>> Hantro H1 (then RK3288) variant. The RK3399 variant was broken,
>>>> producing a JPEG bitstream without the scan, and the capture buffer's
>>>> .bytesused field unset.
>>>>
>>>> Fix this by duplicating the code that is executed when the JPEG encoder
>>>> finishes encoding a frame. As the encoded length is read back from
>>>> hardware, and the variants having different register layouts, the
>>>> code is duplicated rather than shared.
>>>>
>>>> Fixes: e765dba11ec2 ("hantro: Move hantro_enc_buf_finish to JPEG codec_ops.done")
>>>> Signed-off-by: Chen-Yu Tsai <wenst@...omium.org>
>>>> ---
>>>> This was developed on the downstream ChromeOS 5.10 kernel (with a hack
>>>> for .data_offset) and tested with ChromeOS's jpeg_encode_accelerator_unittest
>>>> patched to accept non-JFIF JPEG streams (https://crrev.com/c/3291480).
>>>>
>>>> This was then forward-ported to mainline (name and filename changes) and
>>>> compile tested only.
>>>
>>> Tested with GStreamer on top of 5.16-rc1 from media_stage.git. Not perfect but
>>> at least the the output it valid. Test command was:
>>>
>>>   gst-launch-1.0 videotestsrc num-buffers=2 ! v4l2jpegenc ! filesink
>>> location=test.jpg
>>>
>>> Notice that I encode two frames, it seems like the draining flow is broken in
>>> this driver. GStreamer will queue the frame and issue CMD_START immediately, the
>>> driver will skip the encode, leaving me with an empty file.
>>
>> The hantro driver doesn't implement ENC_CMD, which IIRC is used for the
>> draining flow. I guess that's something to fix, since the mem2mem stateful
>> encoder spec seems to require it. Or does that spec not apply to the JPEG
>> encoders?
> 
> I'm pretty sure its required. But this isn't a regression from this patch.

I don't think it is required for JPEG encoders today. Each frame is independent of
any other, so it behaves just like a m2m scaler for example.

It doesn't hurt to support it, but it shouldn't be necessary for jpeg codecs.

If there is a reason why this is needed, then it would likely also be needed for
m2m devices like scalers.

Regards,

	Hans

> 
>>
>>> Tested-by: Nicolas Dufresne <nicolas.dufresne@...labora.com>
>>
>> Thanks!
>>
>> ChenYu
>