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From:   Maxime Jourdan <mjourdan@baylibre.com>
Date:   Mon, 2 Mar 2020 17:28:38 +0100
Message-ID: <CAMO6nayj8NK1Ete+XcSsiN5R7NNDjG+opxhxTM9pArbRRwcjgw@mail.gmail.com>
Subject: Re: [PATCH 1/4] drm/fourcc: Add modifier definitions for describing
 Amlogic Video Framebuffer Compression
To:     Neil Armstrong <narmstrong@baylibre.com>
Cc:     Daniel Vetter <daniel@ffwll.ch>, dri-devel@lists.freedesktop.org,
        linux-amlogic@lists.infradead.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-arm-kernel@lists.infradead.org
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On Fri, Feb 21, 2020 at 10:09 AM Neil Armstrong <narmstrong@baylibre.com> wrote:
>
> 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.
>
> Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
> ---
>  include/uapi/drm/drm_fourcc.h | 56 +++++++++++++++++++++++++++++++++++
>  1 file changed, 56 insertions(+)
>
> diff --git a/include/uapi/drm/drm_fourcc.h b/include/uapi/drm/drm_fourcc.h
> index 8bc0b31597d8..8a6e87bacadb 100644
> --- a/include/uapi/drm/drm_fourcc.h
> +++ b/include/uapi/drm/drm_fourcc.h
> @@ -309,6 +309,7 @@ extern "C" {
>  #define DRM_FORMAT_MOD_VENDOR_BROADCOM 0x07
>  #define DRM_FORMAT_MOD_VENDOR_ARM     0x08
>  #define DRM_FORMAT_MOD_VENDOR_ALLWINNER 0x09
> +#define DRM_FORMAT_MOD_VENDOR_AMLOGIC 0x0a
>
>  /* add more to the end as needed */
>
> @@ -804,6 +805,61 @@ extern "C" {
>   */
>  #define DRM_FORMAT_MOD_ALLWINNER_TILED fourcc_mod_code(ALLWINNER, 1)
>
> +/*
> + * Amlogic Video Framebuffer Compression modifiers
> + *
> + * 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.
> + * Implementation details may be platform and SoC specific, and shared
> + * between the producer and the decoder on the same platform.
> + *
> + * 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
> + *
> + * The classic memory storage is composed of:
> + * - a body content organized in 64x32 superblocks with 4096 bytes per
> + *   superblock in default mode.
> + * - a 32 bytes per 128x64 header block
> + */
> +#define DRM_FORMAT_MOD_AMLOGIC_FBC_DEFAULT fourcc_mod_code(AMLOGIC, 0)
> +
> +/*
> + * Amlogic Video Framebuffer Compression Options
> + *
> + * Two optional features are available which may not supported/used on every
> + * SoCs and Compressed Framebuffer producers.
> + */
> +#define DRM_FORMAT_MOD_AMLOGIC_FBC(__modes) fourcc_mod_code(AMLOGIC, __modes)
> +
> +/*
> + * Amlogic FBC Scatter Memory layout
> + *
> + * Indicates the header contains IOMMU references to the compressed
> + * frames content to optimize memory access and layout.
> + * In this mode, only the header memory address is needed, thus the
> + * content memory organization is tied to the current producer
> + * execution and cannot be saved/dumped.
> + */
> +#define DRM_FORMAT_MOD_AMLOGIC_FBC_SCATTER     (1ULL << 0)
> +
> +/*
> + * Amlogic FBC Memory Saving mode
> + *
> + * Indicates the storage is packed when pixel size is multiple of word
> + * boudaries, i.e. 8bit should be stored in this mode to save allocation
> + * memory.
> + *
> + * This mode reduces body layout to 3072 bytes per 64x32 superblock and
> + * 3200 bytes per 64x32 superblock combined with scatter mode.
> + */
> +#define DRM_FORMAT_MOD_AMLOGIC_FBC_MEM_SAVING  (1ULL << 1)
> +
>  #if defined(__cplusplus)
>  }
>  #endif
> --
> 2.22.0
>
>

I'm the main developer of the V4L2 video decoder (H264, VP9..) on
amlogic platforms, which is a producer of such compressed frames.

Those modifiers suit well the combinations of options that can be
applied to the frames when created. I also helped testing the
following scenarios of decode+display on various SoCs:

- SM1: DRM_FORMAT_MOD_AMLOGIC_FBC_SCATTER (10-bit & 8-bit video)
- SM1: DRM_FORMAT_MOD_AMLOGIC_FBC_SCATTER +
DRM_FORMAT_MOD_AMLOGIC_FBC_MEM_SAVING (8-bit video)
- G12A: DRM_FORMAT_MOD_AMLOGIC_FBC_SCATTER (10-bit & 8-bit video)
- G12A: DRM_FORMAT_MOD_AMLOGIC_FBC_SCATTER +
DRM_FORMAT_MOD_AMLOGIC_FBC_MEM_SAVING (8-bit video)
- GXL: DRM_FORMAT_MOD_AMLOGIC_FBC_DEFAULT (10-bit & 8-bit video)
- GXL: DRM_FORMAT_MOD_AMLOGIC_FBC_MEM_SAVING (8-bit video)

Reviewed-by: Maxime Jourdan <mjourdan@baylibre.com>