media: mali-c55: Add support for RGB Gamma

Add support for Gamma curve correction for the Mali C55 ISP.

Define a new block in the uAPI using the extensible v4l2-isp format and
implement support for configuring the RGB Gamma parameters in the
mali-c55 parameters handler.

While at it, rename the MALI_C55_REG_GAMMA_GAINS_[1|2] register name
to MALI_C55_REG_GAMMA_GAINS_[RG|B] and the
MALI_C55_REG_GAMMA_OFFSETS_[1|2] register name to
MALI_C55_REG_GAMMA_OFFSETS_[RG|B] to better clarify their intent.

Signed-off-by: Jacopo Mondi <jacopo.mondi+renesas@ideasonboard.com>
Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Reviewed-by: Linus Walleij <linusw@kernel.org>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>

1 files changed, 46 insertions, 1 deletions

diff --git a/include/uapi/linux/media/arm/mali-c55-config.h b/include/uapi/linux/media/arm/mali-c55-config.h
index 0b18863f973d..ef0fe17df96e 100644
--- a/include/uapi/linux/media/arm/mali-c55-config.h
+++ b/include/uapi/linux/media/arm/mali-c55-config.h
@@ -36,6 +36,9 @@
  */
 #define MALI_C55_MAX_ZONES	(15 * 15)
 
+/* Number of RGB gamma LUT entries. */
+#define MALI_C55_NUM_GAMMA_LUT_ELEMENTS 129
+
 /**
  * struct mali_c55_ae_1024bin_hist - Auto Exposure 1024-bin histogram statistics
  *
@@ -220,6 +223,8 @@ struct mali_c55_stats_buffer {
  * @MALI_C55_PARAM_MESH_SHADING_CONFIG : Mesh shading tables configuration
  * @MALI_C55_PARAM_MESH_SHADING_SELECTION: Mesh shading table selection
  * @MALI_C55_PARAM_BLOCK_CCM: Colour correction matrix
+ * @MALI_C55_PARAM_BLOCK_GAMMA_FR: Gamma gain and offset for FR pipe
+ * @MALI_C55_PARAM_BLOCK_GAMMA_DS: Gamma gain and offset for DS pipe
  */
 enum mali_c55_param_block_type {
 	MALI_C55_PARAM_BLOCK_SENSOR_OFFS,
@@ -234,6 +239,8 @@ enum mali_c55_param_block_type {
 	MALI_C55_PARAM_MESH_SHADING_CONFIG,
 	MALI_C55_PARAM_MESH_SHADING_SELECTION,
 	MALI_C55_PARAM_BLOCK_CCM,
+	MALI_C55_PARAM_BLOCK_GAMMA_FR,
+	MALI_C55_PARAM_BLOCK_GAMMA_DS,
 };
 
 /**
@@ -796,6 +803,42 @@ struct mali_c55_params_ccm {
 };
 
 /**
+ * struct mali_c55_params_gamma - RGB Gamma correction
+ *
+ * Gamma correction is used to program a standard gamma curve such as the sRGB
+ * one. It provides gains and offsets to implement contrast adjustments.
+ *
+ * Gamma correction is applied on both the FR and DS pipes separately in the RGB
+ * colour domain where the following operations take place:
+ * 1) An offset is subtracted from each colour channel
+ * 2) Each colour channel is multiplied by a gain
+ * 3) The Gamma LUT is applied to each colour channel
+ *
+ * The Gamma LUT has 129 entries where each node is an unsigned 12 bit number.
+ * It is expected that LUT[0]=0 and LUT[128]=0xfff, with the other 127 values
+ * defining the Gamma correction curve. The three gain multipliers are expressed
+ * as 12-bits unsigned Q4.8 fixed-point numbers and the three offsets are
+ * expressed as a 12-bits unsigned integers.
+ *
+ * As one Gamma correction block is available on both the FR and DS pipes, the
+ * header.type field should be set to one of either
+ * MALI_C55_PARAM_BLOCK_GAMMA_FR or MALI_C55_PARAM_BLOCK_GAMMA_DS from
+ * :c:type:`mali_c55_param_block_type`.
+ *
+ * @header:	The Mali-C55 parameters block header
+ * @gains:	Gains for the red, green and blue channel in unsigned Q4.8 format
+ * @offs:	Offsets subtracted from the red, green and blue channels
+ *		in unsigned 12 bits format
+ * @lut:	129-node Gamma LUT in unsigned 12 bits format
+ */
+struct mali_c55_params_gamma {
+	struct v4l2_isp_params_block_header header;
+	__u16 gains[3];
+	__u16 offs[3];
+	__u32 lut[MALI_C55_NUM_GAMMA_LUT_ELEMENTS];
+};
+
+/**
  * define MALI_C55_PARAMS_MAX_SIZE - Maximum size of all Mali C55 Parameters
  *
  * Though the parameters for the Mali-C55 are passed as optional blocks, the
@@ -819,6 +862,8 @@ struct mali_c55_params_ccm {
 	sizeof(struct mali_c55_params_awb_gains) +		\
 	sizeof(struct mali_c55_params_mesh_shading_config) +	\
 	sizeof(struct mali_c55_params_mesh_shading_selection) +	\
-	sizeof(struct mali_c55_params_ccm))
+	sizeof(struct mali_c55_params_ccm) +			\
+	sizeof(struct mali_c55_params_gamma) +			\
+	sizeof(struct mali_c55_params_gamma))
 
 #endif /* __UAPI_MALI_C55_CONFIG_H */