Re: [PATCH 1/2] drm/fourcc: Add Synaptics VideoSmart tiled modifiers

[Tomasz Figa]

Hi Randy,

On Tue, Aug 9, 2022 at 1:28 AM Hsia-Jun Li <randy.li@xxxxxxxxxxxxx> wrote:
>
> From: "Hsia-Jun(Randy) Li" <randy.li@xxxxxxxxxxxxx>
>
> Memory Traffic Reduction(MTR) is a module in Synaptics
> VideoSmart platform could process lossless compression image
> and cache the tile memory line.
>
> Those modifiers only record the parameters would effort pixel
> layout or memory layout. Whether physical memory page mapping
> is used is not a part of format.
>
> We would allocate the same size of memory for uncompressed
> and compressed luma and chroma data, while the compressed buffer
> would request two extra planes holding the metadata for
> the decompression.
>
> The reason why we need to allocate the same size of memory for
> the compressed frame:
> 1. The compression ratio is not fixed and differnt platforms could
> use a different compression protocol. These protocols are complete
> vendor proprietaries, the other device won't be able to use them.
> It is not necessary to define the version of them here.
>
> 2. Video codec could discard the compression attribute when the
> intra block copy applied to this frame. It would waste lots of
> time on re-allocation.
>
> I am wondering if it is better to add an addtional plane property to
> describe whether the current framebuffer is compressed?
> While the compression flag is still a part of format modifier,
> because it would have two extra meta data planes in the compression
> version.
>
> Signed-off-by: Hsia-Jun(Randy) Li <randy.li@xxxxxxxxxxxxx>
> ---
>  include/uapi/drm/drm_fourcc.h | 49 +++++++++++++++++++++++++++++++++++
>  1 file changed, 49 insertions(+)
>
> diff --git a/include/uapi/drm/drm_fourcc.h b/include/uapi/drm/drm_fourcc.h
> index 0206f812c569..b67884e8bc69 100644
> --- a/include/uapi/drm/drm_fourcc.h
> +++ b/include/uapi/drm/drm_fourcc.h
> @@ -381,6 +381,7 @@ extern "C" {
>  #define DRM_FORMAT_MOD_VENDOR_ARM     0x08
>  #define DRM_FORMAT_MOD_VENDOR_ALLWINNER 0x09
>  #define DRM_FORMAT_MOD_VENDOR_AMLOGIC 0x0a
> +#define DRM_FORMAT_MOD_VENDOR_SYNAPTICS 0x0b
>
>  /* add more to the end as needed */
>
> @@ -1452,6 +1453,54 @@ drm_fourcc_canonicalize_nvidia_format_mod(__u64 modifier)
>  #define AMD_FMT_MOD_CLEAR(field) \
>         (~((__u64)AMD_FMT_MOD_##field##_MASK << AMD_FMT_MOD_##field##_SHIFT))
>
> +/*
> + * Synaptics VideoSmart modifiers
> + *
> + *       Macro
> + * Bits  Param Description
> + * ----  ----- -----------------------------------------------------------------
> + *
> + *  7:0  f     Scan direction description.
> + *
> + *               0 = Invalid
> + *               1 = V4, the scan would always start from vertical for 4 pixel
> + *                   then move back to the start pixel of the next horizontal
> + *                   direction.
> + *               2 = Reserved for future use.

I guess 2..255 are all reserved for future use?

> + *
> + * 15:8  m     The times of pattern repeat in the right angle direction from
> + *             the first scan direction.
> + *
> + * 19:16 p     The padding bits after the whole scan, could be zero.

What is the meaning of "scan" and "whole scan" here?

Best regards,
Tomasz

> + *
> + * 35:20 -     Reserved for future use.  Must be zero.
> + *
> + * 36:36 c     Compression flag.
> + *
> + * 55:37 -     Reserved for future use.  Must be zero.
> + *
> + */
> +
> +#define DRM_FORMAT_MOD_SYNA_V4_TILED           fourcc_mod_code(SYNAPTICS, 1)
> +
> +#define DRM_FORMAT_MOD_SYNA_MTR_LINEAR_2D(f, m, p, c) \
> +       fourcc_mod_code(SYNAPTICS, (((f) & 0xff) | \
> +                                (((m) & 0xff) << 8) | \
> +                                (((p) & 0xf) << 16) | \
> +                                (((c) & 0x1) << 36)))
> +
> +#define DRM_FORMAT_MOD_SYNA_V4H1 \
> +       DRM_FORMAT_MOD_SYNA_MTR_LINEAR_2D(1, 1, 0, 0)
> +
> +#define DRM_FORMAT_MOD_SYNA_V4H3P8 \
> +       DRM_FORMAT_MOD_SYNA_MTR_LINEAR_2D(1, 3, 8, 0)
> +
> +#define DRM_FORMAT_MOD_SYNA_V4H1_COMPRESSED \
> +       DRM_FORMAT_MOD_SYNA_MTR_LINEAR_2D(1, 1, 0, 1)
> +
> +#define DRM_FORMAT_MOD_SYNA_V4H3P8_COMPRESSED \
> +       DRM_FORMAT_MOD_SYNA_MTR_LINEAR_2D(1, 3, 8, 1)
> +
>  #if defined(__cplusplus)
>  }
>  #endif
> --
> 2.17.1
>