linux-kernel - Re: [PATCH v8 0/6] drm/meson: add support for Amlogic Video FBC

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Date:   Thu, 02 Jul 2020 11:57:38 -0700
From:   Kevin Hilman <khilman@...libre.com>
To:     Neil Armstrong <narmstrong@...libre.com>, daniel@...ll.ch,
        dri-devel@...ts.freedesktop.org
Cc:     jianxin.pan@...ogic.com, Neil Armstrong <narmstrong@...libre.com>,
        linux-amlogic@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 0/6] drm/meson: add support for Amlogic Video FBC

Neil Armstrong <narmstrong@...libre.com> 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 layout are supported :
> - Basic: composed of a body and a header
> - Scatter: 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
>
> At least two options are supported :
> - 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.

Reviewed-by: Kevin Hilman <khilman@...libre.com>

Kevin