drm/dsc: Add helpers for DSC picture parameter set infoframes

According to Display Stream compression spec 1.2, the picture
parameter set metadata is sent from source to sink device
using the DP Secondary data packet. An infoframe is formed
for the PPS SDP header and PPS SDP payload bytes.
This patch adds helpers to fill the PPS SDP header
and PPS SDP payload according to the DSC 1.2 specification.

v7:
* Use BUILD_BUG_ON() to protect changing struct size (Ville)
* Remove typecaseting (Ville)
* Include byteorder.h in drm_dsc.c (Ville)
* Correct kernel doc spacing (Anusha)
v6:
* Use proper sequence points for breaking down the
assignments (Chris Wilson)
* Use SPDX identifier
v5:
Do not use bitfields for DRM structs (Jani N)
v4:
* Use DSC constants for params that dont change across
configurations
v3:
* Add reference to added kernel-docs in
Documentation/gpu/drm-kms-helpers.rst (Daniel Vetter)

v2:
* Add EXPORT_SYMBOL for the drm functions (Manasi)

Cc: dri-devel@lists.freedesktop.org
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
Cc: Anusha Srivatsa <anusha.srivatsa@intel.com>
Cc: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
Reviewed-by: Anusha Srivatsa <anusha.srivatsa@intel.com>
Acked-by: Sean Paul <seanpaul@chromium.org> (For merging through
drm-intel)
Link: https://patchwork.freedesktop.org/patch/msgid/20181127214125.17658-5-manasi.d.navare@intel.com

Documentation/gpu/drm-kms-helpers.rst

@@ -232,6 +232,18 @@ MIPI DSI Helper Functions Reference
 .. kernel-doc:: drivers/gpu/drm/drm_mipi_dsi.c
    :export:
 
+Display Stream Compression Helper Functions Reference
+=====================================================
+
+.. kernel-doc:: drivers/gpu/drm/drm_dsc.c
+   :doc: dsc helpers
+
+.. kernel-doc:: include/drm/drm_dsc.h
+   :internal:
+
+.. kernel-doc:: drivers/gpu/drm/drm_dsc.c
+   :export:
+
 Output Probing Helper Functions Reference
 =========================================
 

drivers/gpu/drm/Makefile

@@ -32,7 +32,7 @@ drm-$(CONFIG_AGP) += drm_agpsupport.o
 drm-$(CONFIG_DEBUG_FS) += drm_debugfs.o drm_debugfs_crc.o
 drm-$(CONFIG_DRM_LOAD_EDID_FIRMWARE) += drm_edid_load.o
 
-drm_kms_helper-y := drm_crtc_helper.o drm_dp_helper.o drm_probe_helper.o \
+drm_kms_helper-y := drm_crtc_helper.o drm_dp_helper.o drm_dsc.o drm_probe_helper.o \
 		drm_plane_helper.o drm_dp_mst_topology.o drm_atomic_helper.o \
 		drm_kms_helper_common.o drm_dp_dual_mode_helper.o \
 		drm_simple_kms_helper.o drm_modeset_helper.o \

drivers/gpu/drm/drm_dsc.c

+// SPDX-License-Identifier: MIT
+/*
+ * Copyright © 2018 Intel Corp
+ *
+ * Author:
+ * Manasi Navare <manasi.d.navare@intel.com>
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/errno.h>
+#include <linux/byteorder/generic.h>
+#include <drm/drm_dp_helper.h>
+#include <drm/drm_dsc.h>
+
+/**
+ * DOC: dsc helpers
+ *
+ * These functions contain some common logic and helpers to deal with VESA
+ * Display Stream Compression standard required for DSC on Display Port/eDP or
+ * MIPI display interfaces.
+ */
+
+/**
+ * drm_dsc_dp_pps_header_init() - Initializes the PPS Header
+ * for DisplayPort as per the DP 1.4 spec.
+ * @pps_sdp: Secondary data packet for DSC Picture Parameter Set
+ */
+void drm_dsc_dp_pps_header_init(struct drm_dsc_pps_infoframe *pps_sdp)
+{
+	memset(&pps_sdp->pps_header, 0, sizeof(pps_sdp->pps_header));
+
+	pps_sdp->pps_header.HB1 = DP_SDP_PPS;
+	pps_sdp->pps_header.HB2 = DP_SDP_PPS_HEADER_PAYLOAD_BYTES_MINUS_1;
+}
+EXPORT_SYMBOL(drm_dsc_dp_pps_header_init);
+
+/**
+ * drm_dsc_pps_infoframe_pack() - Populates the DSC PPS infoframe
+ * using the DSC configuration parameters in the order expected
+ * by the DSC Display Sink device. For the DSC, the sink device
+ * expects the PPS payload in the big endian format for the fields
+ * that span more than 1 byte.
+ *
+ * @pps_sdp:
+ * Secondary data packet for DSC Picture Parameter Set
+ * @dsc_cfg:
+ * DSC Configuration data filled by driver
+ */
+void drm_dsc_pps_infoframe_pack(struct drm_dsc_pps_infoframe *pps_sdp,
+				const struct drm_dsc_config *dsc_cfg)
+{
+	int i;
+
+	/* Protect against someone accidently changing struct size */
+	BUILD_BUG_ON(sizeof(pps_sdp->pps_payload) !=
+		     DP_SDP_PPS_HEADER_PAYLOAD_BYTES_MINUS_1 + 1);
+
+	memset(&pps_sdp->pps_payload, 0, sizeof(pps_sdp->pps_payload));
+
+	/* PPS 0 */
+	pps_sdp->pps_payload.dsc_version =
+		dsc_cfg->dsc_version_minor |
+		dsc_cfg->dsc_version_major << DSC_PPS_VERSION_MAJOR_SHIFT;
+
+	/* PPS 1, 2 is 0 */
+
+	/* PPS 3 */
+	pps_sdp->pps_payload.pps_3 =
+		dsc_cfg->line_buf_depth |
+		dsc_cfg->bits_per_component << DSC_PPS_BPC_SHIFT;
+
+	/* PPS 4 */
+	pps_sdp->pps_payload.pps_4 =
+		((dsc_cfg->bits_per_pixel & DSC_PPS_BPP_HIGH_MASK) >>
+		 DSC_PPS_MSB_SHIFT) |
+		dsc_cfg->vbr_enable << DSC_PPS_VBR_EN_SHIFT |
+		dsc_cfg->enable422 << DSC_PPS_SIMPLE422_SHIFT |
+		dsc_cfg->convert_rgb << DSC_PPS_CONVERT_RGB_SHIFT |
+		dsc_cfg->block_pred_enable << DSC_PPS_BLOCK_PRED_EN_SHIFT;
+
+	/* PPS 5 */
+	pps_sdp->pps_payload.bits_per_pixel_low =
+		(dsc_cfg->bits_per_pixel & DSC_PPS_LSB_MASK);
+
+	/*
+	 * The DSC panel expects the PPS packet to have big endian format
+	 * for data spanning 2 bytes. Use a macro cpu_to_be16() to convert
+	 * to big endian format. If format is little endian, it will swap
+	 * bytes to convert to Big endian else keep it unchanged.
+	 */
+
+	/* PPS 6, 7 */
+	pps_sdp->pps_payload.pic_height = cpu_to_be16(dsc_cfg->pic_height);
+
+	/* PPS 8, 9 */
+	pps_sdp->pps_payload.pic_width = cpu_to_be16(dsc_cfg->pic_width);
+
+	/* PPS 10, 11 */
+	pps_sdp->pps_payload.slice_height = cpu_to_be16(dsc_cfg->slice_height);
+
+	/* PPS 12, 13 */
+	pps_sdp->pps_payload.slice_width = cpu_to_be16(dsc_cfg->slice_width);
+
+	/* PPS 14, 15 */
+	pps_sdp->pps_payload.chunk_size = cpu_to_be16(dsc_cfg->slice_chunk_size);
+
+	/* PPS 16 */
+	pps_sdp->pps_payload.initial_xmit_delay_high =
+		((dsc_cfg->initial_xmit_delay &
+		  DSC_PPS_INIT_XMIT_DELAY_HIGH_MASK) >>
+		 DSC_PPS_MSB_SHIFT);
+
+	/* PPS 17 */
+	pps_sdp->pps_payload.initial_xmit_delay_low =
+		(dsc_cfg->initial_xmit_delay & DSC_PPS_LSB_MASK);
+
+	/* PPS 18, 19 */
+	pps_sdp->pps_payload.initial_dec_delay =
+		cpu_to_be16(dsc_cfg->initial_dec_delay);
+
+	/* PPS 20 is 0 */
+
+	/* PPS 21 */
+	pps_sdp->pps_payload.initial_scale_value =
+		dsc_cfg->initial_scale_value;
+
+	/* PPS 22, 23 */
+	pps_sdp->pps_payload.scale_increment_interval =
+		cpu_to_be16(dsc_cfg->scale_increment_interval);
+
+	/* PPS 24 */
+	pps_sdp->pps_payload.scale_decrement_interval_high =
+		((dsc_cfg->scale_decrement_interval &
+		  DSC_PPS_SCALE_DEC_INT_HIGH_MASK) >>
+		 DSC_PPS_MSB_SHIFT);
+
+	/* PPS 25 */
+	pps_sdp->pps_payload.scale_decrement_interval_low =
+		(dsc_cfg->scale_decrement_interval & DSC_PPS_LSB_MASK);
+
+	/* PPS 26[7:0], PPS 27[7:5] RESERVED */
+
+	/* PPS 27 */
+	pps_sdp->pps_payload.first_line_bpg_offset =
+		dsc_cfg->first_line_bpg_offset;
+
+	/* PPS 28, 29 */
+	pps_sdp->pps_payload.nfl_bpg_offset =
+		cpu_to_be16(dsc_cfg->nfl_bpg_offset);
+
+	/* PPS 30, 31 */
+	pps_sdp->pps_payload.slice_bpg_offset =
+		cpu_to_be16(dsc_cfg->slice_bpg_offset);
+
+	/* PPS 32, 33 */
+	pps_sdp->pps_payload.initial_offset =
+		cpu_to_be16(dsc_cfg->initial_offset);
+
+	/* PPS 34, 35 */
+	pps_sdp->pps_payload.final_offset = cpu_to_be16(dsc_cfg->final_offset);
+
+	/* PPS 36 */
+	pps_sdp->pps_payload.flatness_min_qp = dsc_cfg->flatness_min_qp;
+
+	/* PPS 37 */
+	pps_sdp->pps_payload.flatness_max_qp = dsc_cfg->flatness_max_qp;
+
+	/* PPS 38, 39 */
+	pps_sdp->pps_payload.rc_model_size =
+		cpu_to_be16(DSC_RC_MODEL_SIZE_CONST);
+
+	/* PPS 40 */
+	pps_sdp->pps_payload.rc_edge_factor = DSC_RC_EDGE_FACTOR_CONST;
+
+	/* PPS 41 */
+	pps_sdp->pps_payload.rc_quant_incr_limit0 =
+		dsc_cfg->rc_quant_incr_limit0;
+
+	/* PPS 42 */
+	pps_sdp->pps_payload.rc_quant_incr_limit1 =
+		dsc_cfg->rc_quant_incr_limit1;
+
+	/* PPS 43 */
+	pps_sdp->pps_payload.rc_tgt_offset = DSC_RC_TGT_OFFSET_LO_CONST |
+		DSC_RC_TGT_OFFSET_HI_CONST << DSC_PPS_RC_TGT_OFFSET_HI_SHIFT;
+
+	/* PPS 44 - 57 */
+	for (i = 0; i < DSC_NUM_BUF_RANGES - 1; i++)
+		pps_sdp->pps_payload.rc_buf_thresh[i] =
+			dsc_cfg->rc_buf_thresh[i];
+
+	/* PPS 58 - 87 */
+	/*
+	 * For DSC sink programming the RC Range parameter fields
+	 * are as follows: Min_qp[15:11], max_qp[10:6], offset[5:0]
+	 */
+	for (i = 0; i < DSC_NUM_BUF_RANGES; i++) {
+		pps_sdp->pps_payload.rc_range_parameters[i] =
+			((dsc_cfg->rc_range_params[i].range_min_qp <<
+			  DSC_PPS_RC_RANGE_MINQP_SHIFT) |
+			 (dsc_cfg->rc_range_params[i].range_max_qp <<
+			  DSC_PPS_RC_RANGE_MAXQP_SHIFT) |
+			 (dsc_cfg->rc_range_params[i].range_bpg_offset));
+		pps_sdp->pps_payload.rc_range_parameters[i] =
+			cpu_to_be16(pps_sdp->pps_payload.rc_range_parameters[i]);
+	}
+
+	/* PPS 88 */
+	pps_sdp->pps_payload.native_422_420 = dsc_cfg->native_422 |
+		dsc_cfg->native_420 << DSC_PPS_NATIVE_420_SHIFT;
+
+	/* PPS 89 */
+	pps_sdp->pps_payload.second_line_bpg_offset =
+		dsc_cfg->second_line_bpg_offset;
+
+	/* PPS 90, 91 */
+	pps_sdp->pps_payload.nsl_bpg_offset =
+		cpu_to_be16(dsc_cfg->nsl_bpg_offset);
+
+	/* PPS 92, 93 */
+	pps_sdp->pps_payload.second_line_offset_adj =
+		cpu_to_be16(dsc_cfg->second_line_offset_adj);
+
+	/* PPS 94 - 127 are O */
+}
+EXPORT_SYMBOL(drm_dsc_pps_infoframe_pack);

include/drm/drm_dsc.h

@@ -24,6 +24,23 @@
 #define DSC_RC_TGT_OFFSET_HI_CONST	    3
 #define DSC_RC_TGT_OFFSET_LO_CONST	    3
 
+/* DSC PPS constants and macros */
+#define DSC_PPS_VERSION_MAJOR_SHIFT		4
+#define DSC_PPS_BPC_SHIFT			4
+#define DSC_PPS_MSB_SHIFT			8
+#define DSC_PPS_LSB_MASK			(0xFF << 0)
+#define DSC_PPS_BPP_HIGH_MASK			(0x3 << 8)
+#define DSC_PPS_VBR_EN_SHIFT			2
+#define DSC_PPS_SIMPLE422_SHIFT			3
+#define DSC_PPS_CONVERT_RGB_SHIFT		4
+#define DSC_PPS_BLOCK_PRED_EN_SHIFT		5
+#define DSC_PPS_INIT_XMIT_DELAY_HIGH_MASK	(0x3 << 8)
+#define DSC_PPS_SCALE_DEC_INT_HIGH_MASK		(0xF << 8)
+#define DSC_PPS_RC_TGT_OFFSET_HI_SHIFT		4
+#define DSC_PPS_RC_RANGE_MINQP_SHIFT		11
+#define DSC_PPS_RC_RANGE_MAXQP_SHIFT		6
+#define DSC_PPS_NATIVE_420_SHIFT		1
+
 /* Configuration for a single Rate Control model range */
 struct drm_dsc_rc_range_parameters {
 	/* Min Quantization Parameters allowed for this range */
@@ -458,4 +475,8 @@ struct drm_dsc_pps_infoframe {
 	struct drm_dsc_picture_parameter_set pps_payload;
 } __packed;
 
+void drm_dsc_dp_pps_header_init(struct drm_dsc_pps_infoframe *pps_sdp);
+void drm_dsc_pps_infoframe_pack(struct drm_dsc_pps_infoframe *pps_sdp,
+				const struct drm_dsc_config *dsc_cfg);
+
 #endif /* _DRM_DSC_H_ */