linux-kernel - [PATCH v3 5/7] drm/fourcc: amlogic: Add modifier definitions for Memory Saving option

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Date:   Tue, 24 Mar 2020 15:20:14 +0100
From:   Neil Armstrong <narmstrong@...libre.com>
To:     daniel@...ll.ch, dri-devel@...ts.freedesktop.org
Cc:     ppaalanen@...il.com, mjourdan@...libre.com, brian.starkey@....com,
        Neil Armstrong <narmstrong@...libre.com>,
        linux-amlogic@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH v3 5/7] drm/fourcc: amlogic: Add modifier definitions for Memory Saving option

Amlogic uses a proprietary lossless image compression protocol and format
for their hardware video codec accelerators, either video decoders or
video input encoders.

An option exist changing the layout superblock size to save memory when
using 8bit components pixels size.

The layout options starts at the 8th bit, keeping the first 8bits of the
modifiers bits to define the layout.

Signed-off-by: Neil Armstrong <narmstrong@...libre.com>
---
 include/uapi/drm/drm_fourcc.h | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/include/uapi/drm/drm_fourcc.h b/include/uapi/drm/drm_fourcc.h
index 6564813d2f7a..84edc5d69613 100644
--- a/include/uapi/drm/drm_fourcc.h
+++ b/include/uapi/drm/drm_fourcc.h
@@ -819,6 +819,12 @@ extern "C" {
  * per component YCbCr 420, single plane :
  * - DRM_FORMAT_YUV420_8BIT
  * - DRM_FORMAT_YUV420_10BIT
+ *
+ * The first 8 bits of the mode defines the layout, then the following 8 bits
+ * defined the options changing the layout.
+ *
+ * Not all combinations are valid, and different SoCs may support different
+ * combinations of layout and options.
  */
 #define DRM_FORMAT_MOD_AMLOGIC_FBC(__modes) fourcc_mod_code(AMLOGIC, __modes)
 
@@ -834,6 +840,22 @@ extern "C" {
  */
 #define DRM_FORMAT_MOD_AMLOGIC_FBC_LAYOUT_BASIC		(1ULL << 0)
 
+/*
+ * Amlogic FBC Layout Options
+ */
+
+/*
+ * 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 with
+ * the basic layout.
+ */
+#define DRM_FORMAT_MOD_AMLOGIC_FBC_MEM_SAVING	(1ULL << 8)
+
 #if defined(__cplusplus)
 }
 #endif
-- 
2.22.0