Re: [PATCH 5/7] arm64: dts: allwinner: sun50i-h6: Add missing SRAM region for video engine

[Paul Kocialkowski <paulk@sys-base.io>]

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Hi Chen-Yu,

On Tue 05 May 26, 21:48, Chen-Yu Tsai wrote:
> The SRAM C region contains a partial alias to the VE SRAM already
> referenced by the video engine. To avoid access through this alias
> window, the region should also be claimed by the video engine.
> 
> Add a reference to the SRAM C region to the video engine node.

It feels very weird to have a reference to the DE2 SRAM region in the
VE node. It seems unlikely that the same region would be used by both DE2 and
VE and I am pretty sure can have both running at the same time without
overstepping.

From what I can see we have so far assumed that the SRAM C and SRAM C1
are two different physical SRAM areas, but this is most likely not the case.
My guess would be that SRAM C1 is actually a part of SRAM C and the DE2 is
using another part of it. The syscon block probably allows switching access
to these different parts of SRAM C.

Also the sram_c1 node implies it's 2 MiB, which sounds quite unlikely.

All the best,

Paul

> 
> Fixes: b542570e5605 ("arm64: dts: allwinner: h6: Add Video Engine node")
> Signed-off-by: Chen-Yu Tsai <wens@kernel.org>
> ---
>  arch/arm64/boot/dts/allwinner/sun50i-h6.dtsi | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/boot/dts/allwinner/sun50i-h6.dtsi b/arch/arm64/boot/dts/allwinner/sun50i-h6.dtsi
> index 72ce1a75647b..88c6e3e105c0 100644
> --- a/arch/arm64/boot/dts/allwinner/sun50i-h6.dtsi
> +++ b/arch/arm64/boot/dts/allwinner/sun50i-h6.dtsi
> @@ -205,7 +205,7 @@ video-codec@1c0e000 {
>  			clock-names = "ahb", "mod", "ram";
>  			resets = <&ccu RST_BUS_VE>;
>  			interrupts = <GIC_SPI 89 IRQ_TYPE_LEVEL_HIGH>;
> -			allwinner,sram = <&ve_sram 1>;
> +			allwinner,sram = <&ve_sram 1>, <&de2_sram 1>;
>  			iommus = <&iommu 3>;
>  		};
>  
> -- 
> 2.47.3
> 

-- 
Paul Kocialkowski,

Independent contractor - sys-base - https://www.sys-base.io/
Free software developer - https://www.paulk.fr/

Expert in multimedia, graphics and embedded hardware support with Linux.

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