Subject: Re: [PATCH 0/4] drm/meson: add support for Amlogic Video FBC

From: Kevin Hilman <[email-masked]>
Date: Mon, 02 Mar 2020 17:25:06 +0100

Neil Armstrong <[email-masked]> writes:

> Amlogic uses a proprietary lossless image compression protocol and format
> for their hardware video codec accelerators, either video decoders or
> video input encoders.
>
> It considerably reduces memory bandwidth while writing and reading
> frames in memory.
>
> The underlying storage is considered to be 3 components, 8bit or 10-bit
> per component, YCbCr 420, single plane :
> - DRM_FORMAT_YUV420_8BIT
> - DRM_FORMAT_YUV420_10BIT
>
> This modifier will be notably added to DMA-BUF frames imported from the V4L2
> Amlogic VDEC decoder.
>
> At least two options are supported :
> - Scatter mode: the buffer is filled with a IOMMU scatter table referring
>   to the encoder current memory layout. This mode if more efficient in terms
>   of memory allocation but frames are not dumpable and only valid during until
>   the buffer is freed and back in control of the encoder
> - Memory saving: when the pixel bpp is 8b, the size of the superblock can
>   be reduced, thus saving memory.
>
> This serie adds the missing register, updated the FBC decoder registers
> content to be committed by the crtc code.
>
> The Amlogic FBC has been tested with compressed content from the Amlogic
> HW VP9 decoder on S905X (GXL), S905D2 (G12A) and S905X3 (SM1) in 8bit
> (Scatter+Mem Saving on G12A/SM1, Mem Saving on GXL) and 10bit
> (Scatter on G12A/SM1, default on GXL).
>
> It's expected to work as-is on GXM and G12B SoCs.

Tested on meson-sm1-sei610 with 4k@60p (VP9) streams.

Tested-by: Kevin Hilman <[email-masked]>

Kevin

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