linux-kernel - Re: [PATCH v3 2/2] media: amphion: Add a frame flush mode for decoder

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Message-ID: <20250327074835.r47kaabtwu5jqvxf@basti-XPS-13-9310>
Date: Thu, 27 Mar 2025 08:48:35 +0100
From: Sebastian Fricke <sebastian.fricke@...labora.com>
To: ming.qian@....nxp.com
Cc: mchehab@...nel.org, hverkuil-cisco@...all.nl, nicolas@...fresne.ca,
	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 2/2] media: amphion: Add a frame flush mode for decoder

Hey Ming,

On 05.03.2025 14:26, ming.qian@....nxp.com wrote:
>From: Ming Qian <ming.qian@....nxp.com>
>
>By default the amphion decoder will pre-parse 3 frames before starting
>to decode the first frame. Alternatively, a block of flush padding data
>can be appended to the frame, which will ensure that the decoder can
>start decoding immediately after parsing the flush padding data, thus
>potentially reducing decoding latency.
>
>This mode was previously only enabled, when the display delay was set to
>0. Allow the user to manually toggle the use of that mode via a module
>parameter called frame_flush_mode, which enables the mode without
>changing the display order.
>
>Signed-off-by: Ming Qian <ming.qian@....nxp.com>
>---
>v3
>- Improve commit message as recommended
>- Add some comments to avoid code looks cryptic
>
> drivers/media/platform/amphion/vpu_malone.c | 14 +++++++++++++-
> 1 file changed, 13 insertions(+), 1 deletion(-)
>
>diff --git a/drivers/media/platform/amphion/vpu_malone.c b/drivers/media/platform/amphion/vpu_malone.c
>index 1d9e10d9bec1..4ef9810d8142 100644
>--- a/drivers/media/platform/amphion/vpu_malone.c
>+++ b/drivers/media/platform/amphion/vpu_malone.c
>@@ -25,6 +25,10 @@
> #include "vpu_imx8q.h"
> #include "vpu_malone.h"
>
>+static bool frame_flush_mode;
>+module_param(frame_flush_mode, bool, 0644);
>+MODULE_PARM_DESC(frame_flush_mode, "Set low latency flush mode: 0 (disable) or 1 (enable)");
>+
> #define CMD_SIZE			25600
> #define MSG_SIZE			25600
> #define CODEC_SIZE			0x1000
>@@ -1579,7 +1583,15 @@ static int vpu_malone_input_frame_data(struct vpu_malone_str_buffer __iomem *str
>
> 	vpu_malone_update_wptr(str_buf, wptr);
>
>-	if (disp_imm && !vpu_vb_is_codecconfig(vbuf)) {
>+	/*
>+	 * Enable the low latency flush mode if display delay is set to 0
>+	 * or parameter frame_flush_mode is set to 1.

s/or parameter frame_flush_mode is set to 1./
   or the frame flush mode if it is set to 1./

>+	 * The low latency flush mode requires some padding data to be appended after each frame,

s/appended after each/appended to each/
(the word append implies that something is added after something else)

>+	 * but don't put it in between the sequence header and frame.

s/but don't put it in between the sequence header and frame./
   but there must not be any padding data between the sequence header and the frame./

(As this is not a suggestion for the developer but a description of what
the code does)

>+	 * Only H264 and HEVC decoder support this module yet,

s/decoder/formats/

I'd rewrite this part:
This module is currently only supported for the H264 and HEVC formats,

but that is only because this sounds more natural to me.

>+	 * for other formats, vpu_malone_add_scode() will return 0.
>+	 */
>+	if ((disp_imm || frame_flush_mode) && !vpu_vb_is_codecconfig(vbuf)) {
> 		ret = vpu_malone_add_scode(inst->core->iface,
> 					   inst->id,
> 					   &inst->stream_buffer,
>-- 
>2.43.0-rc1
>
>

Thank you!

Regards,
Sebastian Fricke