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Date:   Mon, 3 Jul 2023 12:53:38 +0200
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Subject: Re: [PATCH v3 04/11] media: videobuf2: Stop define VB2_MAX_FRAME as
 global
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To:     Hsia-Jun Li <Randy.Li@synaptics.com>
Cc:     linux-media@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, m.szyprowski@samsung.com,
        linux-mediatek@lists.infradead.org, linux-arm-msm@vger.kernel.org,
        hverkuil-cisco@xs4all.nl, ezequiel@vanguardiasur.com.ar,
        p.zabel@pengutronix.de, linux-rockchip@lists.infradead.org,
        mchehab@kernel.org, linux-staging@lists.linux.dev,
        ming.qian@nxp.com, kernel@collabora.com,
        gregkh@linuxfoundation.org, tfiga@chromium.org,
        nicolas.dufresne@collabora.com
References: <20230622131349.144160-1-benjamin.gaignard@collabora.com>
 <20230622131349.144160-5-benjamin.gaignard@collabora.com>
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 <5cb3f216-5041-a155-5d2c-059dc1f15024@collabora.com>
 <25b21252-0d3a-3e50-0012-57055f386fee@synaptics.com>
From:   Benjamin Gaignard <benjamin.gaignard@collabora.com>
In-Reply-To: <25b21252-0d3a-3e50-0012-57055f386fee@synaptics.com>
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Le 03/07/2023 à 10:35, Hsia-Jun Li a écrit :
>
> On 7/3/23 16:09, Benjamin Gaignard wrote:
>> CAUTION: Email originated externally, do not click links or open 
>> attachments unless you recognize the sender and know the content is 
>> safe.
>>
>>
>> Le 30/06/2023 à 11:51, Hsia-Jun Li a écrit :
>>>
>>> On 6/22/23 21:13, Benjamin Gaignard wrote:
>>>> CAUTION: Email originated externally, do not click links or open
>>>> attachments unless you recognize the sender and know the content is
>>>> safe.
>>>>
>>>>
>>>> After changing bufs arrays to a dynamic allocated array
>>>> VB2_MAX_FRAME doesn't mean anything for videobuf2 core.
>>>
>>> I think make it 64 which is the VB2_MAX_FRAME in Android GKI kernel is
>>> more reasonable.
>>>
>>> It would be hard to iterate the whole array, it would go worse with a
>>> filter. Such iterate may need to go twice because you mix
>>> post-processing buffer and decoding buffer(with MV) in the same array.
>>
>> Here I don't want to change drivers behavior so I keep the same value.
>> If it happens that they need more buffers, like for dynamic 
>> resolution change
>> feature for Verisilicon VP9 decoder, case by case patches will be 
>> needed.
>>
> I just don't like the idea that using a variant length array here.

As far I have understand Hans and/or Laurent were happy to use that but I may have misunderstood them.

>
> And I could explain why you won't need so many buffers for the 
> performance of decoding.
>
> VP9 could support 10 reference frames in dpb.
>
> Even for those frequent resolution changing test set, it would only 
> happen to two resolutions,
>
> 32 would be enough for 20 buffers of two resolution plus golden 
> frames. It also leaves enough slots for re-order latency.
>
> If your case had more two resolutions, likes low->medium->high.

VP9 header doesn't tell you that video resolution will change and in which way.
It cloud be from factor x1/2 to x16 and multiple time so you can use lot of (too much) buffers.

>
> I would suggest just skip the medium resolutions, just allocate the 
> lower one first for fast playback then the highest for all the possible
>
> medium cases. Reallocation happens frequently would only cause memory 
> fragment, nothing benefits your performance.
>
>>
>>>
>>>> Remove it from the core definitions but keep it for drivers internal
>>>> needs.
>>>>
>>>> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
>>>> ---
>>>>   drivers/media/common/videobuf2/videobuf2-core.c | 2 ++
>>>>   drivers/media/platform/amphion/vdec.c | 1 +
>>>> .../media/platform/mediatek/vcodec/vdec/vdec_vp9_req_lat_if.c | 2 ++
>>>>   drivers/media/platform/qcom/venus/hfi.h | 2 ++
>>>>   drivers/media/platform/verisilicon/hantro_hw.h | 2 ++
>>>>   drivers/staging/media/ipu3/ipu3-v4l2.c | 2 ++
>>>>   include/media/videobuf2-core.h | 1 -
>>>>   include/media/videobuf2-v4l2.h | 4 ----
>>>>   8 files changed, 11 insertions(+), 5 deletions(-)
>>>>
>>>> diff --git a/drivers/media/common/videobuf2/videobuf2-core.c
>>>> b/drivers/media/common/videobuf2/videobuf2-core.c
>>>> index 86e1e926fa45..899783f67580 100644
>>>> --- a/drivers/media/common/videobuf2/videobuf2-core.c
>>>> +++ b/drivers/media/common/videobuf2/videobuf2-core.c
>>>> @@ -31,6 +31,8 @@
>>>>
>>>>   #include <trace/events/vb2.h>
>>>>
>>>> +#define VB2_MAX_FRAME  32
>>>> +
>>>>   static int debug;
>>>>   module_param(debug, int, 0644);
>>>>
>>>> diff --git a/drivers/media/platform/amphion/vdec.c
>>>> b/drivers/media/platform/amphion/vdec.c
>>>> index 3fa1a74a2e20..b3219f6d17fa 100644
>>>> --- a/drivers/media/platform/amphion/vdec.c
>>>> +++ b/drivers/media/platform/amphion/vdec.c
>>>> @@ -28,6 +28,7 @@
>>>>
>>>>   #define VDEC_MIN_BUFFER_CAP            8
>>>>   #define VDEC_MIN_BUFFER_OUT            8
>>>> +#define VB2_MAX_FRAME                  32
>>>>
>>>>   struct vdec_fs_info {
>>>>          char name[8];
>>>> diff --git
>>>> a/drivers/media/platform/mediatek/vcodec/vdec/vdec_vp9_req_lat_if.c
>>>> b/drivers/media/platform/mediatek/vcodec/vdec/vdec_vp9_req_lat_if.c
>>>> index 6532a69f1fa8..a1e0f24bb91c 100644
>>>> --- 
>>>> a/drivers/media/platform/mediatek/vcodec/vdec/vdec_vp9_req_lat_if.c
>>>> +++ 
>>>> b/drivers/media/platform/mediatek/vcodec/vdec/vdec_vp9_req_lat_if.c
>>>> @@ -16,6 +16,8 @@
>>>>   #include "../vdec_drv_if.h"
>>>>   #include "../vdec_vpu_if.h"
>>>>
>>>> +#define VB2_MAX_FRAME  32
>>>> +
>>>>   /* reset_frame_context defined in VP9 spec */
>>>>   #define VP9_RESET_FRAME_CONTEXT_NONE0 0
>>>>   #define VP9_RESET_FRAME_CONTEXT_NONE1 1
>>>> diff --git a/drivers/media/platform/qcom/venus/hfi.h
>>>> b/drivers/media/platform/qcom/venus/hfi.h
>>>> index f25d412d6553..bd5ca5a8b945 100644
>>>> --- a/drivers/media/platform/qcom/venus/hfi.h
>>>> +++ b/drivers/media/platform/qcom/venus/hfi.h
>>>> @@ -10,6 +10,8 @@
>>>>
>>>>   #include "hfi_helper.h"
>>>>
>>>> +#define VB2_MAX_FRAME                          32
>>>> +
>>>>   #define VIDC_SESSION_TYPE_VPE                  0
>>>>   #define VIDC_SESSION_TYPE_ENC                  1
>>>>   #define VIDC_SESSION_TYPE_DEC                  2
>>>> diff --git a/drivers/media/platform/verisilicon/hantro_hw.h
>>>> b/drivers/media/platform/verisilicon/hantro_hw.h
>>>> index e83f0c523a30..9e8faf7ba6fb 100644
>>>> --- a/drivers/media/platform/verisilicon/hantro_hw.h
>>>> +++ b/drivers/media/platform/verisilicon/hantro_hw.h
>>>> @@ -15,6 +15,8 @@
>>>>   #include <media/v4l2-vp9.h>
>>>>   #include <media/videobuf2-core.h>
>>>>
>>>> +#define VB2_MAX_FRAME  32
>>>> +
>>>>   #define DEC_8190_ALIGN_MASK    0x07U
>>>>
>>>>   #define MB_DIM                 16
>>>> diff --git a/drivers/staging/media/ipu3/ipu3-v4l2.c
>>>> b/drivers/staging/media/ipu3/ipu3-v4l2.c
>>>> index e530767e80a5..6627b5c2d4d6 100644
>>>> --- a/drivers/staging/media/ipu3/ipu3-v4l2.c
>>>> +++ b/drivers/staging/media/ipu3/ipu3-v4l2.c
>>>> @@ -10,6 +10,8 @@
>>>>   #include "ipu3.h"
>>>>   #include "ipu3-dmamap.h"
>>>>
>>>> +#define VB2_MAX_FRAME  32
>>>> +
>>>>   /******************** v4l2_subdev_ops ********************/
>>>>
>>>>   #define IPU3_RUNNING_MODE_VIDEO                0
>>>> diff --git a/include/media/videobuf2-core.h
>>>> b/include/media/videobuf2-core.h
>>>> index 77921cf894ef..080b783d608d 100644
>>>> --- a/include/media/videobuf2-core.h
>>>> +++ b/include/media/videobuf2-core.h
>>>> @@ -20,7 +20,6 @@
>>>>   #include <media/media-request.h>
>>>>   #include <media/frame_vector.h>
>>>>
>>>> -#define VB2_MAX_FRAME  (32)
>>>>   #define VB2_MAX_PLANES (8)
>>>>
>>>>   /**
>>>> diff --git a/include/media/videobuf2-v4l2.h
>>>> b/include/media/videobuf2-v4l2.h
>>>> index 5a845887850b..88a7a565170e 100644
>>>> --- a/include/media/videobuf2-v4l2.h
>>>> +++ b/include/media/videobuf2-v4l2.h
>>>> @@ -15,10 +15,6 @@
>>>>   #include <linux/videodev2.h>
>>>>   #include <media/videobuf2-core.h>
>>>>
>>>> -#if VB2_MAX_FRAME != VIDEO_MAX_FRAME
>>>> -#error VB2_MAX_FRAME != VIDEO_MAX_FRAME
>>>> -#endif
>>>> -
>>>>   #if VB2_MAX_PLANES != VIDEO_MAX_PLANES
>>>>   #error VB2_MAX_PLANES != VIDEO_MAX_PLANES
>>>>   #endif
>>>> -- 
>>>> 2.39.2
>>>>