[PATCH v3 6/7] video: Only dcache flush damaged lines

[Heinrich Schuchardt]

On 12/30/22 20:58, Alexander Graf wrote:
> Now that we have a damage area tells us which parts of the frame buffer
> actually need updating, let's only dcache flush those on video_sync()
> calls. With this optimization in place, frame buffer updates - especially
> on large screen such as 4k displays - speed up significantly.
>
> Signed-off-by: Alexander Graf <agraf at csgraf.de>
> Reported-by: Da Xue <da at libre.computer>
>
> ---
>
> v1 -> v2:
>
>    - Fix dcache range; we were flushing too much before
>    - Remove ifdefs
> ---
>   drivers/video/video-uclass.c | 51 ++++++++++++++++++++++++++++++------
>   1 file changed, 43 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/video/video-uclass.c b/drivers/video/video-uclass.c
> index f1fbeaadcb..bf93f524c7 100644
> --- a/drivers/video/video-uclass.c
> +++ b/drivers/video/video-uclass.c
> @@ -297,9 +297,45 @@ int video_damage(struct udevice *vid, int x, int y, int width, int height)
>   	return 0;
>   }
>
> +#if defined(CONFIG_ARM) && !CONFIG_IS_ENABLED(SYS_DCACHE_OFF)

ARM isn't the only architecture implementing flush_dcache_range().
So this condition needs to be fixed as well as the one in video_sync.

Why don't you simply rely on priv->flash_dcache irrespective of the
architecture? Let the video drivers decide if they need it.

Best regards

Heinrich

> +static void video_flush_dcache(struct udevice *vid)
> +{
> +	struct video_priv *priv = dev_get_uclass_priv(vid);
> +
> +	if (!priv->flush_dcache)
> +		return;
> +
> +	if (!CONFIG_IS_ENABLED(VIDEO_DAMAGE)) {
> +		flush_dcache_range((ulong)priv->fb,
> +				   ALIGN((ulong)priv->fb + priv->fb_size,
> +					 CONFIG_SYS_CACHELINE_SIZE));
> +
> +		return;
> +	}
> +
> +	if (priv->damage.endx && priv->damage.endy) {
> +		int lstart = priv->damage.x * VNBYTES(priv->bpix);
> +		int lend = priv->damage.endx * VNBYTES(priv->bpix);
> +		int y;
> +
> +		for (y = priv->damage.y; y < priv->damage.endy; y++) {
> +			ulong fb = (ulong)priv->fb;
> +			ulong start = fb + (y * priv->line_length) + lstart;
> +			ulong end = start + lend - lstart;
> +
> +			start = ALIGN_DOWN(start, CONFIG_SYS_CACHELINE_SIZE);
> +			end = ALIGN(end, CONFIG_SYS_CACHELINE_SIZE);
> +
> +			flush_dcache_range(start, end);
> +		}
> +	}
> +}
> +#endif
> +
>   /* Flush video activity to the caches */
>   int video_sync(struct udevice *vid, bool force)
>   {
> +	struct video_priv *priv = dev_get_uclass_priv(vid);
>   	struct video_ops *ops = video_get_ops(vid);
>   	int ret;
>
> @@ -315,15 +351,8 @@ int video_sync(struct udevice *vid, bool force)
>   	 * out whether it exists? For now, ARM is safe.
>   	 */
>   #if defined(CONFIG_ARM) && !CONFIG_IS_ENABLED(SYS_DCACHE_OFF)
> -	struct video_priv *priv = dev_get_uclass_priv(vid);
> -
> -	if (priv->flush_dcache) {
> -		flush_dcache_range((ulong)priv->fb,
> -				   ALIGN((ulong)priv->fb + priv->fb_size,
> -					 CONFIG_SYS_CACHELINE_SIZE));
> -	}
> +	video_flush_dcache(vid);
>   #elif defined(CONFIG_VIDEO_SANDBOX_SDL)
> -	struct video_priv *priv = dev_get_uclass_priv(vid);
>   	static ulong last_sync;
>
>   	if (force || get_timer(last_sync) > 100) {
> @@ -331,6 +360,12 @@ int video_sync(struct udevice *vid, bool force)
>   		last_sync = get_timer(0);
>   	}
>   #endif
> +
> +	if (CONFIG_IS_ENABLED(VIDEO_DAMAGE)) {
> +		priv->damage.endx = 0;
> +		priv->damage.endy = 0;
> +	}
> +
>   	return 0;
>   }
>