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

[Nicolas Dufresne]

Le mercredi 05 mars 2025 à 14:26 +0800, ming.qian@xxxxxxxxxxx a écrit :
> From: Ming Qian <ming.qian@xxxxxxxxxxx>
> 
> 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.

Ok, so in short the DISPLAY_DELAY breaks the reodering like intended,
while this module parameter only reduce the delay. Perhaps I'll ask
again, is is compliant or does it break some test vectors ? 

> 
> Signed-off-by: Ming Qian <ming.qian@xxxxxxxxxxx>
> ---
> 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)");

Depending on the explanation, I may come back and suggest a different
name for it. Meanwhile, have you consider simply "low_latency" ?

> +
>  #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.
> +	 * The low latency flush mode requires some padding data to be appended after each frame,
> +	 * but don't put it in between the sequence header and frame.
> +	 * Only H264 and HEVC decoder support this module yet,
> +	 * 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,

In principle I'm fine with adding a module parameters, I just want to
know more about it, perhaps we should add small hints in the
description (or a comment in the code).

Reviewed-by: Nicolas Dufresne <nicolas.dufresne@xxxxxxxxxxxxx>