linux-kernel - Re: [PATCH v3 1/2] media: amphion: Reduce decoding latency for HEVC decoder

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Message-ID: <c61a522d82bd9375e73d6f9c57f8ca4b0de258e0.camel@ndufresne.ca>
Date: Wed, 26 Mar 2025 16:48:01 -0400
From: Nicolas Dufresne <nicolas@...fresne.ca>
To: ming.qian@....nxp.com, mchehab@...nel.org, hverkuil-cisco@...all.nl
Cc: sebastian.fricke@...labora.com, shawnguo@...nel.org,
 s.hauer@...gutronix.de, 	kernel@...gutronix.de, festevam@...il.com,
 linux-imx@....com, xiahong.bao@....com, 	eagle.zhou@....com,
 imx@...ts.linux.dev, linux-media@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3 1/2] media: amphion: Reduce decoding latency for HEVC
 decoder

Hi,

Le mercredi 05 mars 2025 à 14:26 +0800, ming.qian@....nxp.com a écrit :
> From: Ming Qian <ming.qian@....nxp.com>
> 
> The amphion decoder firmware supports a low latency flush mode for the
> HEVC format since v1.9.0. This feature, which is enabled when the
> display delay is set to 0, can help to reduce the decoding latency by
> appending some padding data to every frame.

Just curiosity, does it stay spec compliant or not ? Perhaps share some
compliance (fluster) results ?

> 
> Signed-off-by: Ming Qian <ming.qian@....nxp.com>
> ---
> v3
> - Improve commit message as recommended
> v2
> - Improve commit message
> - Add firmware version check
> 
>  drivers/media/platform/amphion/vpu_malone.c | 22 ++++++++++++++++++---
>  1 file changed, 19 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/media/platform/amphion/vpu_malone.c b/drivers/media/platform/amphion/vpu_malone.c
> index 5c6b2a841b6f..1d9e10d9bec1 100644
> --- a/drivers/media/platform/amphion/vpu_malone.c
> +++ b/drivers/media/platform/amphion/vpu_malone.c
> @@ -68,6 +68,9 @@
>  
>  #define MALONE_DEC_FMT_RV_MASK			BIT(21)
>  
> +#define MALONE_VERSION_MASK			0xFFFFF
> +#define MALONE_MIN_VERSION_HEVC_BUFFLUSH	(((1 << 16) | (9 << 8) | 0) & MALONE_VERSION_MASK)

Just a suggestion, could also use an inline function.

#define MALONE_VERSION(maj, min, inc)   (((maj) << 16) | ((min) << 16) | (inc)) & MALONE_VERSION_MASK)
#define CHECK_VERSION(iface, maj, min)	((iface->fw_version & MALONE_VERSION_MASK) >= MALONE_VERSION(maj, min, 0))

> +
>  enum vpu_malone_stream_input_mode {
>  	INVALID_MODE = 0,
>  	FRAME_LVL,
> @@ -332,6 +335,8 @@ struct vpu_dec_ctrl {
>  	u32 buf_addr[VID_API_NUM_STREAMS];
>  };
>  
> +static const struct malone_padding_scode *get_padding_scode(u32 type, u32 fmt);
> +
>  u32 vpu_malone_get_data_size(void)
>  {
>  	return sizeof(struct vpu_dec_ctrl);
> @@ -654,9 +659,16 @@ static int vpu_malone_set_params(struct vpu_shared_addr *shared,
>  		hc->jpg[instance].jpg_mjpeg_interlaced = 0;
>  	}
>  
> -	hc->codec_param[instance].disp_imm = params->display_delay_enable ? 1 : 0;
> -	if (malone_format != MALONE_FMT_AVC)
> +	if (params->display_delay_enable &&
> +	    get_padding_scode(SCODE_PADDING_BUFFLUSH, params->codec_format))
> +		hc->codec_param[instance].disp_imm = 1;
> +	else
>  		hc->codec_param[instance].disp_imm = 0;
> +
> +	if (params->codec_format == V4L2_PIX_FMT_HEVC &&
> +	    (iface->fw_version & MALONE_VERSION_MASK) < MALONE_MIN_VERSION_HEVC_BUFFLUSH)

So if could be:
	    !CHECK_VERSION(iface, 1, 9)

There might be even better ways, this is not a hard request from me
though.

> +		hc->codec_param[instance].disp_imm = 0;
> +
>  	hc->codec_param[instance].dbglog_enable = 0;
>  	iface->dbglog_desc.level = 0;
>  
> @@ -1024,6 +1036,7 @@ static const struct malone_padding_scode padding_scodes[] = {
>  	{SCODE_PADDING_EOS,      V4L2_PIX_FMT_JPEG,        {0x0, 0x0}},
>  	{SCODE_PADDING_BUFFLUSH, V4L2_PIX_FMT_H264,        {0x15010000, 0x0}},
>  	{SCODE_PADDING_BUFFLUSH, V4L2_PIX_FMT_H264_MVC,    {0x15010000, 0x0}},
> +	{SCODE_PADDING_BUFFLUSH, V4L2_PIX_FMT_HEVC,        {0x3e010000, 0x20}},
>  };
>  
>  static const struct malone_padding_scode padding_scode_dft = {0x0, 0x0};
> @@ -1058,8 +1071,11 @@ static int vpu_malone_add_padding_scode(struct vpu_buffer *stream_buffer,
>  	int ret;
>  
>  	ps = get_padding_scode(scode_type, pixelformat);
> -	if (!ps)
> +	if (!ps) {
> +		if (scode_type == SCODE_PADDING_BUFFLUSH)
> +			return 0;
>  		return -EINVAL;
> +	}
>  
>  	wptr = readl(&str_buf->wptr);
>  	if (wptr < stream_buffer->phys || wptr > stream_buffer->phys + stream_buffer->length)

With or without the adjustments.

Reviewed-by: Nicolas Dufresne <nicolas.dufresne@...labora.com