linux-kernel - Re: [RFC PATCH 04/12] media: iris: Add internal buffer calculation for HEVC and VP9 decoders

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Message-ID: <ac44e16c-36af-471a-b47b-bb26ccd9f018@linaro.org>
Date: Thu, 6 Mar 2025 01:05:50 +0000
From: Bryan O'Donoghue <bryan.odonoghue@...aro.org>
To: Dikshita Agarwal <quic_dikshita@...cinc.com>, quic_vgarodia@...cinc.com,
 quic_abhinavk@...cinc.com, mchehab@...nel.org
Cc: hverkuil@...all.nl, linux-media@...r.kernel.org,
 linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 04/12] media: iris: Add internal buffer calculation
 for HEVC and VP9 decoders

On 05/03/2025 10:43, Dikshita Agarwal wrote:
> Add internal buffer count and size calculations for HEVC and VP9
> decoders.
> 
> Signed-off-by: Dikshita Agarwal <quic_dikshita@...cinc.com>
> ---
>   .../media/platform/qcom/iris/iris_buffer.c    |   3 +
>   .../platform/qcom/iris/iris_vpu_buffer.c      | 397 +++++++++++++++++-
>   .../platform/qcom/iris/iris_vpu_buffer.h      |  46 +-
>   3 files changed, 432 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/media/platform/qcom/iris/iris_buffer.c b/drivers/media/platform/qcom/iris/iris_buffer.c
> index e5c5a564fcb8..8c9d5b7fe75c 100644
> --- a/drivers/media/platform/qcom/iris/iris_buffer.c
> +++ b/drivers/media/platform/qcom/iris/iris_buffer.c
> @@ -205,6 +205,9 @@ static u32 iris_bitstream_buffer_size(struct iris_inst *inst)
>   	if (num_mbs > NUM_MBS_4K) {
>   		div_factor = 4;
>   		base_res_mbs = caps->max_mbpf;
> +	} else {
> +		if (inst->codec == V4L2_PIX_FMT_VP9)
> +			div_factor = 1;
>   	}
>   
>   	/*
> diff --git a/drivers/media/platform/qcom/iris/iris_vpu_buffer.c b/drivers/media/platform/qcom/iris/iris_vpu_buffer.c
> index dce25e410d80..13ee93356bcb 100644
> --- a/drivers/media/platform/qcom/iris/iris_vpu_buffer.c
> +++ b/drivers/media/platform/qcom/iris/iris_vpu_buffer.c
> @@ -31,6 +31,42 @@ static u32 hfi_buffer_bin_h264d(u32 frame_width, u32 frame_height, u32 num_vpp_p
>   	return size_h264d_hw_bin_buffer(n_aligned_w, n_aligned_h, num_vpp_pipes);
>   }
>   
> +static u32 size_h265d_hw_bin_buffer(u32 frame_width, u32 frame_height, u32 num_vpp_pipes)
> +{
> +	u32 product = frame_width * frame_height;
> +	u32 size_yuv, size_bin_hdr, size_bin_res;
> +
> +	size_yuv = (product <= BIN_BUFFER_THRESHOLD) ?
> +		((BIN_BUFFER_THRESHOLD * 3) >> 1) : ((product * 3) >> 1);

When I read this code I have no way of knowing if it makes sense.

#define BIN_BUFFER_THRESHOLD		(1280 * 736)

((BIN_BUFFER_THRESHOLD * 3) >> 1)

How/why is that correct ?

> +	size_bin_hdr = size_yuv * H265_CABAC_HDR_RATIO_HD_TOT;
> +	size_bin_res = size_yuv * H265_CABAC_RES_RATIO_HD_TOT;
> +	size_bin_hdr = ALIGN(size_bin_hdr / num_vpp_pipes, DMA_ALIGNMENT) * num_vpp_pipes;
> +	size_bin_res = ALIGN(size_bin_res / num_vpp_pipes, DMA_ALIGNMENT) * num_vpp_pipes;
> +
> +	return size_bin_hdr + size_bin_res;
> +}
> +
> +static u32 hfi_buffer_bin_vp9d(u32 frame_width, u32 frame_height, u32 num_vpp_pipes)
> +{
> +	u32 _size_yuv = ALIGN(frame_width, 16) * ALIGN(frame_height, 16) * 3 / 2;
> +	u32 _size = ALIGN(((max_t(u32, _size_yuv, ((BIN_BUFFER_THRESHOLD * 3) >> 1)) *
> +			VPX_DECODER_FRAME_BIN_HDR_BUDGET / VPX_DECODER_FRAME_BIN_DENOMINATOR *
> +			VPX_DECODER_FRAME_CONCURENCY_LVL) / num_vpp_pipes), DMA_ALIGNMENT) +
> +			ALIGN(((max_t(u32, _size_yuv, ((BIN_BUFFER_THRESHOLD * 3) >> 1)) *
> +			VPX_DECODER_FRAME_BIN_RES_BUDGET / VPX_DECODER_FRAME_BIN_DENOMINATOR *
> +			VPX_DECODER_FRAME_CONCURENCY_LVL) / num_vpp_pipes), DMA_ALIGNMENT);

The size_yuv I guess just about makes sense but the _size component here 
is pretty hard to say whether or not this adds up.

Could you please add some comments to describe the calculations in these 
complex size/alignment clauses.

---
bod