Date:   Mon, 18 Mar 2019 11:17:55 +0100
From:   Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>
To:     Ayan Halder <Ayan.Halder@....com>,
        Liviu Dudau <Liviu.Dudau@....com>,
        Brian Starkey <Brian.Starkey@....com>,
        "malidp@...s.arm.com" <malidp@...s.arm.com>,
        "maxime.ripard@...tlin.com" <maxime.ripard@...tlin.com>,
        "sean@...rly.run" <sean@...rly.run>,
        "airlied@...ux.ie" <airlied@...ux.ie>,
        "daniel@...ll.ch" <daniel@...ll.ch>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "alyssa@...enzweig.io" <alyssa@...enzweig.io>
Cc:     nd <nd@....com>, Daniel Vetter <daniel.vetter@...ll.ch>,
        Dave Airlie <airlied@...il.com>,
        Swati Sharma <swati2.sharma@...el.com>,
        Juha-Pekka Heikkila <juhapekka.heikkila@...il.com>,
        Vidya Srinivas <vidya.srinivas@...el.com>
Subject: Re: [PATCH v4 01/10] drm/fourcc: Add AFBC yuv fourccs for Mali

Op 12-03-2019 om 19:16 schreef Ayan Halder:
> From: Brian Starkey <brian.starkey@....com>
>
> As we look to enable AFBC using DRM format modifiers, we run into
> problems which we've historically handled via vendor-private details
> (i.e. gralloc, on Android).
>
> AFBC (as an encoding) is fully flexible, and for example YUV data can
> be encoded into 1, 2 or 3 encoded "planes", much like the linear
> equivalents. Component order is also meaningful, as AFBC doesn't
> necessarily care about what each "channel" of the data it encodes
> contains. Therefore ABGR8888 and RGBA8888 can be encoded in AFBC with
> different representations. Similarly, 'X' components may be encoded
> into AFBC streams in cases where a decoder expects to decode a 4th
> component.
>
> In addition, AFBC is a licensable IP, meaning that to support the
> ecosystem we need to ensure that _all_ AFBC users are able to describe
> the encodings that they need. This is much better achieved by
> preserving meaning in the fourcc codes when they are combined with an
> AFBC modifier.
>
> In essence, we want to use the modifier to describe the parameters of
> the AFBC encode/decode, and use the fourcc code to describe the data
> being encoded/decoded.
>
> To do anything different would be to introduce redundancy - we would
> need to duplicate in the modifier information which is _already_
> conveyed clearly and non-ambigiously by a fourcc code.
>
> I hope that for RGB this is non-controversial.
> (BGRA8888 + MODIFIER_AFBC) is a different format from
> (RGBA8888 + MODIFIER_AFBC).
>
> Possibly more controversial is that (XBGR8888 + MODIFIER_AFBC)
> is different from (BGR888 + MODIFIER_AFBC). I understand that in some
> schemes it is not the case - but in AFBC it is so.
>
> Where we run into problems is where there are not already fourcc codes
> which represent the data which the AFBC encoder/decoder is processing.
> To that end, we want to introduce new fourcc codes to describe the
> data being encoded/decoded, in the places where none of the existing
> fourcc codes are applicable.
>
> Where we don't support an equivalent non-compressed layout, or where
> no "obvious" linear layout exists, we are proposing adding fourcc
> codes which have no associated linear layout - because any layout we
> proposed would be completely arbitrary.
>
> Some formats are following the naming conventions from [2].
>
> The summary of the new formats is:
>  DRM_FORMAT_VUY888 - Packed 8-bit YUV 444. Y followed by U then V.
>  DRM_FORMAT_VUY101010 - Packed 10-bit YUV 444. Y followed by U then
>                         V. No defined linear encoding.
>  DRM_FORMAT_Y210 - Packed 10-bit YUV 422. Y followed by U (then Y)
>                    then V. 10-bit samples in 16-bit words.
>  DRM_FORMAT_Y410 - Packed 10-bit YUV 444, with 2-bit alpha.
>  DRM_FORMAT_P210 - Semi-planar 10-bit YUV 422. Y plane, followed by
>                    interleaved U-then-V plane. 10-bit samples in
>                    16-bit words.
>  DRM_FORMAT_YUV420_8BIT - Packed 8-bit YUV 420. Y followed by U then
>                           V. No defined linear encoding
>  DRM_FORMAT_YUV420_10BIT - Packed 10-bit YUV 420. Y followed by U
>                            then V. No defined linear encoding
>
> Please also note that in the absence of AFBC, we would still need to
> add Y410, Y210 and P210.
>
> Full rationale follows:
>
> YUV 444 8-bit, 1-plane
> ----------------------
>  The currently defined AYUV format encodes a 4th alpha component,
>  which makes it unsuitable for representing a 3-component YUV 444
>  AFBC stream.
>
>  The proposed[1] XYUV format which is supported by Mali-DP in linear
>  layout is also unsuitable, because the component order is the
>  opposite of the AFBC version, and it encodes a 4th 'X' component.
>
>  DRM_FORMAT_VUY888 is the "obvious" format for a 3-component, packed,
>  YUV 444 8-bit format, with the component order which our HW expects to
>  encode/decode. It conforms to the same naming convention as the
>  existing packed YUV 444 format.
>  The naming here is meant to be consistent with DRM_FORMAT_AYUV and
>  DRM_FORMAT_XYUV[1]
>
> YUV 444 10-bit, 1-plane
> -----------------------
>  There is no currently-defined YUV 444 10-bit format in
>  drm_fourcc.h, irrespective of number of planes.
>
>  The proposed[1] XVYU2101010 format which is supported by Mali-DP in
>  linear layout uses the wrong component order, and also encodes a 4th
>  'X' component, which doesn't match the AFBC version of YUV 444
>  10-bit which we support.
>
>  DRM_FORMAT_Y410 is the same layout as XVYU2101010, but with 2 bits of
>  alpha.  This format is supported with linear layout by Mali GPUs. The
>  naming follows[2].
>
>  There is no "obvious" linear encoding for a 3-component 10:10:10
>  packed format, and so DRM_FORMAT_VUY101010 defines a component
>  order, but not a bit encoding. Again, the naming is meant to be
>  consistent with DRM_FORMAT_AYUV.
>
> YUV 422 8-bit, 1-plane
> ----------------------
>  The existing DRM_FORMAT_YUYV (and the other component orders) are
>  single-planar YUV 422 8-bit formats. Following the convention of
>  the component orders of the RGB formats, YUYV has the correct
>  component order for our AFBC encoding (Y followed by U followed by
>  V). We can use YUYV for AFBC YUV 422 8-bit.
>
> YUV 422 10-bit, 1-plane
> -----------------------
>  There is no currently-defined YUV 422 10-bit format in drm_fourcc.h
>
>  DRM_FORMAT_Y210 is analogous to YUYV, but with 10-bits per sample
>  packed into the upper 10-bits of 16-bit samples. This format is
>  supported in both linear and AFBC by Mali GPUs.
>
> YUV 422 10-bit, 2-plane
> -----------------------
>  The recently defined DRM_FORMAT_P010 format is a 10-bit semi-planar
>  YUV 420 format, which has the correct component ordering for an AFBC
>  2-plane YUV 420 buffer. The linear layout contains meaningless padding
>  bits, which will not be encoded in an AFBC stream.
>
> YUV 420 8-bit, 1-plane
> ----------------------
>  There is no currently defined single-planar YUV 420, 8-bit format
>  in drm_fourcc.h. There's differing opinions on whether using the
>  existing fourcc-implied n_planes where possible is a good idea or
>  not when using modifiers.
>
>  For me, it's much more "obvious" to use NV12 for 2-plane AFBC and
>  YUV420 for 3-plane AFBC. This keeps the aforementioned separation
>  between the AFBC codec settings (in the modifier) and the pixel data
>  format (in the fourcc). With different vendors using AFBC, this helps
>  to ensure that there is no confusion in interoperation. It also
>  ensures that the AFBC modifiers describe AFBC itself (which is a
>  licensable component), and not implementation details which are not
>  defined by AFBC.
>
>  The proposed[1] X0L0 format which Mali-DP supports with Linear layout
>  is unsuitable, as it contains a 4th 'X' component, and our AFBC
>  decoder expects only 3 components.
>
>  To that end, we propose a new YUV 420 8-bit format. There is no
>  "obvious" linear encoding for a 3-component 8:8:8, 420, packed format,
>  and so DRM_FORMAT_YUV420_8BIT defines a component order, but not a
>  bit encoding. I'm happy to hear different naming suggestions.
>
> YUV 420 8-bit, 2-, 3-plane
> --------------------------
>  These already exist, we can use NV12 and YUV420.
>
> YUV 420 10-bit, 1-plane
> -----------------------
>  As above, no current definition exists, and X0L2 encodes a 4th 'X'
>  channel.
>
>  Analogous to DRM_FORMAT_YUV420_8BIT, we define DRM_FORMAT_YUV420_10BIT.
>
> [1] https://lists.freedesktop.org/archives/dri-devel/2018-July/184598.html
> [2] https://docs.microsoft.com/en-us/windows/desktop/medfound/10-bit-and-16-bit-yuv-video-formats
>
> Changes since RFC v1:
>  - Fix confusing subsampling vs bit-depth X:X:X notation in
>    descriptions (danvet)
>  - Rename DRM_FORMAT_AVYU1101010 to DRM_FORMAT_Y410 (Lisa Wu)
>  - Add drm_format_info structures for the new formats, using the
>    new 'bpp' field for those with non-integer bytes-per-pixel
>  - Rebase, including Juha-Pekka Heikkila's format definitions
>
> Changes since RFC v2:
> - Rebase on top of latest changes in drm-misc-next
> - Change the description of DRM_FORMAT_P210 in __drm_format_info and
> drm_fourcc.h so as to make it consistent with other DRM_FORMAT_PXXX
> formats.
>
> Changes since v3:
> - Added the ack
> - Rebased on the latest drm-misc-next
>
> Signed-off-by: Brian Starkey <brian.starkey@....com>
> Signed-off-by: Ayan Kumar Halder <ayan.halder@....com>
> Reviewed-by: Liviu Dudau <liviu.dudau@....com>
> Acked-by: Alyssa Rosenzweig <alyssa@...enzweig.io>
> ---
>  drivers/gpu/drm/drm_fourcc.c  | 16 ++++++++++++++++
>  include/uapi/drm/drm_fourcc.h | 20 ++++++++++++++++++++
>  2 files changed, 36 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_fourcc.c b/drivers/gpu/drm/drm_fourcc.c
> index 45c9882..a9df743 100644
> --- a/drivers/gpu/drm/drm_fourcc.c
> +++ b/drivers/gpu/drm/drm_fourcc.c
> @@ -225,6 +225,9 @@ const struct drm_format_info *__drm_format_info(u32 format)
>  		{ .format = DRM_FORMAT_UYVY,		.depth = 0,  .num_planes = 1, .cpp = { 2, 0, 0 }, .hsub = 2, .vsub = 1, .is_yuv = true },
>  		{ .format = DRM_FORMAT_VYUY,		.depth = 0,  .num_planes = 1, .cpp = { 2, 0, 0 }, .hsub = 2, .vsub = 1, .is_yuv = true },
>  		{ .format = DRM_FORMAT_XYUV8888,	.depth = 0,  .num_planes = 1, .cpp = { 4, 0, 0 }, .hsub = 1, .vsub = 1, .is_yuv = true },
> +		{ .format = DRM_FORMAT_Y210,		.depth = 0,  .num_planes = 1, .cpp = { 4, 0, 0 }, .hsub = 2, .vsub = 1, .is_yuv = true },
> +		{ .format = DRM_FORMAT_VUY888,          .depth = 0,  .num_planes = 1, .cpp = { 3, 0, 0 }, .hsub = 1, .vsub = 1, .is_yuv = true },
> +		{ .format = DRM_FORMAT_Y410,            .depth = 0,  .num_planes = 1, .cpp = { 4, 0, 0 }, .hsub = 1, .vsub = 1, .has_alpha = true, .is_yuv = true },
>  		{ .format = DRM_FORMAT_AYUV,		.depth = 0,  .num_planes = 1, .cpp = { 4, 0, 0 }, .hsub = 1, .vsub = 1, .has_alpha = true, .is_yuv = true },
>  		{ .format = DRM_FORMAT_Y210,            .depth = 0,  .num_planes = 1, .cpp = { 4, 0, 0 }, .hsub = 2, .vsub = 1, .is_yuv = true },
>  		{ .format = DRM_FORMAT_Y212,            .depth = 0,  .num_planes = 1, .cpp = { 4, 0, 0 }, .hsub = 2, .vsub = 1, .is_yuv = true },
> @@ -253,6 +256,19 @@ const struct drm_format_info *__drm_format_info(u32 format)
>  		{ .format = DRM_FORMAT_P016,		.depth = 0,  .num_planes = 2,
>  		  .char_per_block = { 2, 4, 0 }, .block_w = { 1, 0, 0 }, .block_h = { 1, 0, 0 },
>  		  .hsub = 2, .vsub = 2, .is_yuv = true},
> +		{ .format = DRM_FORMAT_P210,		.depth = 0,
> +		  .num_planes = 2, .char_per_block = { 2, 4, 0 },
> +		  .block_w = { 1, 0, 0 }, .block_h = { 1, 0, 0 }, .hsub = 2,
> +		  .vsub = 1, .is_yuv = true },
> +		{ .format = DRM_FORMAT_VUY101010,	.depth = 0,
> +		  .num_planes = 1, .cpp = { 0, 0, 0 }, .hsub = 1, .vsub = 1,
> +		  .is_yuv = true },
> +		{ .format = DRM_FORMAT_YUV420_8BIT,     .depth = 0,
> +		  .num_planes = 1, .cpp = { 0, 0, 0 }, .hsub = 2, .vsub = 2,
> +		  .is_yuv = true },
> +		{ .format = DRM_FORMAT_YUV420_10BIT,    .depth = 0,
> +		  .num_planes = 1, .cpp = { 0, 0, 0 }, .hsub = 2, .vsub = 2,
> +		  .is_yuv = true },
>  	};
>  
>  	unsigned int i;
> diff --git a/include/uapi/drm/drm_fourcc.h b/include/uapi/drm/drm_fourcc.h
> index 9fa7cf7..b992a38 100644
> --- a/include/uapi/drm/drm_fourcc.h
> +++ b/include/uapi/drm/drm_fourcc.h
> @@ -149,9 +149,13 @@ extern "C" {
>  #define DRM_FORMAT_YVYU		fourcc_code('Y', 'V', 'Y', 'U') /* [31:0] Cb0:Y1:Cr0:Y0 8:8:8:8 little endian */
>  #define DRM_FORMAT_UYVY		fourcc_code('U', 'Y', 'V', 'Y') /* [31:0] Y1:Cr0:Y0:Cb0 8:8:8:8 little endian */
>  #define DRM_FORMAT_VYUY		fourcc_code('V', 'Y', 'U', 'Y') /* [31:0] Y1:Cb0:Y0:Cr0 8:8:8:8 little endian */
> +#define DRM_FORMAT_Y210		fourcc_code('Y', '2', '1', '0') /* [63:0] Cr0:0:Y1:0:Cb0:0:Y0:0 10:6:10:6:10:6:10:6 little endian */
>  
>  #define DRM_FORMAT_AYUV		fourcc_code('A', 'Y', 'U', 'V') /* [31:0] A:Y:Cb:Cr 8:8:8:8 little endian */
>  #define DRM_FORMAT_XYUV8888		fourcc_code('X', 'Y', 'U', 'V') /* [31:0] X:Y:Cb:Cr 8:8:8:8 little endian */
> +#define DRM_FORMAT_VUY888	fourcc_code('V', 'U', '2', '4') /* [23:0] Cr:Cb:Y 8:8:8 little endian */
> +#define DRM_FORMAT_Y410		fourcc_code('Y', '4', '1', '0') /* [31:0] A:Cr:Y:Cb 2:10:10:10 little endian */
> +#define DRM_FORMAT_VUY101010	fourcc_code('V', 'U', '3', '0') /* Y followed by U then V, 10:10:10. Non-linear modifier only */
>  
>  /*
>   * packed Y2xx indicate for each component, xx valid data occupy msb
> @@ -184,6 +188,15 @@ extern "C" {
>  #define DRM_FORMAT_X0L2		fourcc_code('X', '0', 'L', '2')
>  
>  /*
> + * 1-plane YUV 4:2:0
> + * In these formats, the component ordering is specified (Y, followed by U
> + * then V), but the exact Linear layout is undefined.
> + * These formats can only be used with a non-Linear modifier.
> + */
> +#define DRM_FORMAT_YUV420_8BIT	fourcc_code('Y', 'U', '0', '8')
> +#define DRM_FORMAT_YUV420_10BIT	fourcc_code('Y', 'U', '1', '0')
> +
> +/*
>   * 2 plane RGB + A
>   * index 0 = RGB plane, same format as the corresponding non _A8 format has
>   * index 1 = A plane, [7:0] A
> @@ -216,6 +229,13 @@ extern "C" {
>   * index 0 = Y plane, [15:0] Y:x [10:6] little endian
>   * index 1 = Cr:Cb plane, [31:0] Cr:x:Cb:x [10:6:10:6] little endian
>   */
> +#define DRM_FORMAT_P210		fourcc_code('P', '2', '1', '0') /* 2x1 subsampled Cr:Cb plane, 10 bit per channel */
> +
> +/*
> + * 2 plane YCbCr MSB aligned
> + * index 0 = Y plane, [15:0] Y:x [10:6] little endian
> + * index 1 = Cr:Cb plane, [31:0] Cr:x:Cb:x [10:6:10:6] little endian
> + */
>  #define DRM_FORMAT_P010		fourcc_code('P', '0', '1', '0') /* 2x2 subsampled Cr:Cb plane 10 bits per channel */
>  
>  /*

Hey..

There's a conflict with this patch and the merge of topic/hdr-formats, resulting in double definitions for Y210, Y410 and P010.

Worse still is that one has set has_alpha to true for Y41x and other to false.

~Maarten

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