[6/6] video: Only dcache flush damaged lines

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@csgraf.de>
Reported-by: Da Xue <da@libre.computer>
---
 drivers/video/video-uclass.c | 49 ++++++++++++++++++++++++++++++------
 1 file changed, 42 insertions(+), 7 deletions(-)

On 6/7/22 01:43, 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@csgraf.de>
> Reported-by: Da Xue <da@libre.computer>
> ---
>   drivers/video/video-uclass.c | 49 ++++++++++++++++++++++++++++++------
>   1 file changed, 42 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/video/video-uclass.c b/drivers/video/video-uclass.c
> index 9ac1974670..5661beea38 100644
> --- a/drivers/video/video-uclass.c
> +++ b/drivers/video/video-uclass.c
> @@ -222,6 +222,39 @@ int video_damage(struct udevice *vid, int x, int y, int width, int height)
>   }
>   #endif
>   
> +#if defined(CONFIG_ARM) && !CONFIG_IS_ENABLED(SYS_DCACHE_OFF)

Why should this be ARM specific?

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;
> +
> +#ifdef CONFIG_VIDEO_DAMAGE
> +	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;
> +
> +			start = ALIGN_DOWN(start, CONFIG_SYS_CACHELINE_SIZE);
> +			end = ALIGN(end, CONFIG_SYS_CACHELINE_SIZE);
> +
> +			flush_dcache_range(start, end);
> +		}
> +	}
> +#else
> +	flush_dcache_range((ulong)priv->fb,
> +			   ALIGN((ulong)priv->fb + priv->fb_size,
> +				 CONFIG_SYS_CACHELINE_SIZE));
> +#endif
> +}
> +#endif
> +
>   /* Flush video activity to the caches */
>   int video_sync(struct udevice *vid, bool force)
>   {
> @@ -240,13 +273,7 @@ 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;
> @@ -256,6 +283,14 @@ int video_sync(struct udevice *vid, bool force)
>   		last_sync = get_timer(0);
>   	}
>   #endif
> +
> +#ifdef CONFIG_VIDEO_DAMAGE
> +	struct video_priv *priv = dev_get_uclass_priv(vid);
> +
> +	priv->damage.endx = 0;
> +	priv->damage.endy = 0;
> +#endif
> +
>   	return 0;
>   }
>

On 07.06.22 10:00, Heinrich Schuchardt wrote:
> On 6/7/22 01:43, 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@csgraf.de>
>> Reported-by: Da Xue <da@libre.computer>
>> ---
>>   drivers/video/video-uclass.c | 49 ++++++++++++++++++++++++++++++------
>>   1 file changed, 42 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/video/video-uclass.c b/drivers/video/video-uclass.c
>> index 9ac1974670..5661beea38 100644
>> --- a/drivers/video/video-uclass.c
>> +++ b/drivers/video/video-uclass.c
>> @@ -222,6 +222,39 @@ int video_damage(struct udevice *vid, int x, int 
>> y, int width, int height)
>>   }
>>   #endif
>>   +#if defined(CONFIG_ARM) && !CONFIG_IS_ENABLED(SYS_DCACHE_OFF)
>
> Why should this be ARM specific?


I don't believe it should - and that's what the existing comment also 
says. But currently it is because the dcache API isn't available on all 
platforms; I'm merely preserving the existing logic :).


Thanks,

Alex