Re: [PATCH v3] media: iris: optimize COMV buffer allocation for VPU3x and VPU4x

[Vikash Garodia]

On 5/6/2026 11:42 AM, Vishnu Reddy wrote:
> The existing iris_vpu_dec_comv_size() used VIDEO_MAX_FRAME (32) as
> num_comv count unconditionally when calculating the co-located motion
> vector (COMV) buffer size. This resulted in an oversized COMV buffer
> allocation throughout decode session, wasting memory regardless of
> actual number of buffers required.
>
> For VPU3x and VPU4x platforms, introduce iris_vpu3x_4x_dec_comv_size() to
> replace iris_vpu_dec_comv_size(). These derive num_comv dynamically, it
> uses inst->fw_min_count once the firmware has reported its buffer
> requirements, and fallback to output count during initialization before
> firmware has communicated its requirements. This aligns the COMV buffer
> size to the actual count needed rather than always allocating with fixed
> VIDEO_MAX_FRAME value.
>
> Additionally, during iris_vdec_inst_init(), fw_min_count was initialized
> to MIN_BUFFERS instead of 0. This masked the fallback logic and caused the
> COMV size calculation to use MIN_BUFFERS even before firmware had reported
> its actual requirements. Fix this by initializing fw_min_count to 0.
>
> During testing of 1080p AVC, it reduces the COMV buffer size from 32.89MB
> to 6.16MB per decode session, significantly reducing memory consumption.
>
> Signed-off-by: Vishnu Reddy<busanna.reddy@xxxxxxxxxxxxxxxx>
> ---

Reviewed-by: Vikash Garodia <vikash.garodia@xxxxxxxxxxxxxxxx>