[PATCH v3 10/10] media: aspeed: add a workaround to fix a silicon bug

[Jae Hyun Yoo <jae.hyun.yoo@linux.intel.com>]

Hi Eddie,

All patches in this series were queued to linux/media tree except this
one. Can you please review this patch?

Thanks,
Jae

On 5/31/2019 3:15 PM, Jae Hyun Yoo wrote:
> AST2500 silicon revision A1 and A2 have a silicon bug which causes
> extremly long capturing time on specific resolutions (1680 width).
> To fix the bug, this commit adjusts the capturing window register
> setting to 1728 if detected width is 1680. The compression window
> register setting will be kept as the original width so output
> result will be the same.
> 
> Signed-off-by: Jae Hyun Yoo <jae.hyun.yoo@linux.intel.com>
> ---
> v2 -> v3:
>   Added more detail comments why the value 1728 is picked.
> 
> v1 -> v2:
>   New.
> 
>   drivers/media/platform/aspeed-video.c | 28 ++++++++++++++++++++-------
>   1 file changed, 21 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/media/platform/aspeed-video.c b/drivers/media/platform/aspeed-video.c
> index ba093096a5a7..f899ac3b4a61 100644
> --- a/drivers/media/platform/aspeed-video.c
> +++ b/drivers/media/platform/aspeed-video.c
> @@ -824,8 +824,29 @@ static void aspeed_video_set_resolution(struct aspeed_video *video)
>   	struct v4l2_bt_timings *act = &video->active_timings;
>   	unsigned int size = act->width * act->height;
>   
> +	/* Set capture/compression frame sizes */
>   	aspeed_video_calc_compressed_size(video, size);
>   
> +	if (video->active_timings.width == 1680) {
> +		/*
> +		 * This is a workaround to fix a silicon bug on A1 and A2
> +		 * revisions. Since it doesn't break capturing operation of
> +		 * other revisions, use it for all revisions without checking
> +		 * the revision ID. It picked 1728 which is a very next
> +		 * 64-pixels aligned value to 1680 to minimize memory bandwidth
> +		 * and to get better access speed from video engine.
> +		 */
> +		aspeed_video_write(video, VE_CAP_WINDOW,
> +				   1728 << 16 | act->height);
> +		size += (1728 - 1680) * video->active_timings.height;
> +	} else {
> +		aspeed_video_write(video, VE_CAP_WINDOW,
> +				   act->width << 16 | act->height);
> +	}
> +	aspeed_video_write(video, VE_COMP_WINDOW,
> +			   act->width << 16 | act->height);
> +	aspeed_video_write(video, VE_SRC_SCANLINE_OFFSET, act->width * 4);
> +
>   	/* Don't use direct mode below 1024 x 768 (irqs don't fire) */
>   	if (size < DIRECT_FETCH_THRESHOLD) {
>   		aspeed_video_write(video, VE_TGS_0,
> @@ -842,13 +863,6 @@ static void aspeed_video_set_resolution(struct aspeed_video *video)
>   		aspeed_video_update(video, VE_CTRL, 0, VE_CTRL_DIRECT_FETCH);
>   	}
>   
> -	/* Set capture/compression frame sizes */
> -	aspeed_video_write(video, VE_CAP_WINDOW,
> -			   act->width << 16 | act->height);
> -	aspeed_video_write(video, VE_COMP_WINDOW,
> -			   act->width << 16 | act->height);
> -	aspeed_video_write(video, VE_SRC_SCANLINE_OFFSET, act->width * 4);
> -
>   	size *= 4;
>   
>   	if (size != video->srcs[0].size) {
>