linux-kernel - Re: [PATCH v3 2/5] media: hantro: Reduce H264 extra space for motion vectors

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Date:   Wed, 08 Jan 2020 15:10:27 +0000 (UTC)
From:   Jonas Karlman <jonas@...boo.se>
To:     Tomasz Figa <tfiga@...omium.org>,
        Ezequiel Garcia <ezequiel@...labora.com>
Cc:     Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
        Hans Verkuil <hverkuil@...all.nl>,
        Boris Brezillon <boris.brezillon@...labora.com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        "linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 2/5] media: hantro: Reduce H264 extra space for motion
 vectors

On 2020-01-08 13:59, Tomasz Figa wrote:
> On Tue, Dec 10, 2019 at 3:11 AM Ezequiel Garcia <ezequiel@...labora.com> wrote:
>>
>> On Wed, 2019-11-20 at 21:44 +0900, Tomasz Figa wrote:
>>> Hi Jonas,
>>>
>>> On Thu, Nov 7, 2019 at 7:34 AM Jonas Karlman <jonas@...boo.se> wrote:
>>>> A decoded 8-bit 4:2:0 frame need memory for up to 448 bytes per
>>>> macroblock with additional 32 bytes on multi-core variants.
>>>>
>>>> Memory layout is as follow:
>>>>
>>>> +---------------------------+
>>>>> Y-plane   256 bytes x MBs |
>>>> +---------------------------+
>>>>> UV-plane  128 bytes x MBs |
>>>> +---------------------------+
>>>>> MV buffer  64 bytes x MBs |
>>>> +---------------------------+
>>>>> MC sync          32 bytes |
>>>> +---------------------------+
>>>>
>>>> Reduce the extra space allocated now that motion vector buffer offset no
>>>> longer is based on the extra space.
>>>>
>>>> Only allocate extra space for 64 bytes x MBs of motion vector buffer
>>>> and 32 bytes for multi-core sync.
>>>>
>>>> Fixes: a9471e25629b ("media: hantro: Add core bits to support H264 decoding")
>>>> Signed-off-by: Jonas Karlman <jonas@...boo.se>
>>>> Reviewed-by: Boris Brezillon <boris.brezillon@...labora.com>
>>>> ---
>>>> Changes in v3:
>>>>   - add memory layout to code comment (Boris)
>>>> Changes in v2:
>>>>   - updated commit message
>>>> ---
>>>>  drivers/staging/media/hantro/hantro_v4l2.c | 20 ++++++++++++++++++--
>>>>  1 file changed, 18 insertions(+), 2 deletions(-)
>>>>
>>>
>>> Thanks for the patch!
>>>
>>> What platform did you test it on and how? Was it tested with IOMMU enabled?
>>
>> Hello Tomasz,
>>
>> Please note that this series has been picked-up and is merged
>> in v5.5-rc1.
>>
>> IIRC, we tested these patches on RK3399 and RK3288 (that means
>> with an IOMMU). I've just ran some more extensive tests on RK3288,
>> on media/master; and I plan to test some more on RK3399 later this week.
>>
>> Do you have any specific concern in mind?
> 
> I specifically want to know whether we're 100% sure that those sizes
> are correct. The IOMMU still works on page granularity so it's
> possible that the allocation could be just big enough by luck.

One of my RK3288 TRM [1] contains the following:

Direct mode motion vector write:
  Its base addr is right after decode output picture data
  Its length is mbwidth*mbheight*64

Also both the mpp library and imx-vpu-hantro code both use mbwidth*mbheight*64.
So I feel confident that the buffer size is correct.

[1] Rockchip RK3288TRM V1.1 Part3-Graphic and multi-media.pdf

Regards,
Jonas

> 
> Best regards,
> Tomasz
>