linux-kernel - [PATCH 1/4] drm/fourcc: Add modifier definitions for describing Amlogic Video Framebuffer Compression

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Date:   Thu, 20 Feb 2020 17:27:55 +0100
From:   Neil Armstrong <narmstrong@...libre.com>
To:     daniel@...ll.ch, dri-devel@...ts.freedesktop.org
Cc:     Neil Armstrong <narmstrong@...libre.com>,
        linux-amlogic@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH 1/4] drm/fourcc: Add modifier definitions for describing Amlogic Video Framebuffer Compression

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@...libre.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 5ba481f49931..ad58f2a92669 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 */
 
@@ -791,6 +792,61 @@ 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