This patch adds appropiate kernel documentation for DRM DP helpers used for enabling Display Stream compression functionality in drm_dp_helper.h and drm_dp_helper.c as well as for the DSC spec related structure definitions and helpers in drm_dsc.c and drm_dsc.h Also add links between the functions and structures in the documentation.
v2: * Add inline comments for longer structs (Daniel Vetter) * Split the summary and description (Daniel Vetter)
Suggested-by: Daniel Vetter daniel.vetter@intel.com Suggested-by: Sean Paul sean@poorly.run Cc: Daniel Vetter daniel.vetter@intel.com Cc: Sean Paul sean@poorly.run Signed-off-by: Manasi Navare manasi.d.navare@intel.com --- drivers/gpu/drm/drm_dp_helper.c | 47 ++++++- drivers/gpu/drm/drm_dsc.c | 30 ++++- include/drm/drm_dp_helper.h | 15 ++- include/drm/drm_dsc.h | 226 ++++++++++++++++++++++++-------- 4 files changed, 252 insertions(+), 66 deletions(-)
diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c index 54120b6319e7..54a6414c5d96 100644 --- a/drivers/gpu/drm/drm_dp_helper.c +++ b/drivers/gpu/drm/drm_dp_helper.c @@ -1360,7 +1360,20 @@ int drm_dp_read_desc(struct drm_dp_aux *aux, struct drm_dp_desc *desc, EXPORT_SYMBOL(drm_dp_read_desc);
/** - * DRM DP Helpers for DSC + * drm_dp_dsc_sink_max_slice_count() - Get the max slice count + * supported by the DSC sink. + * @dsc_dpcd: DSC capabilities from DPCD + * @is_edp: true if its eDP, false for DP + * + * Read the slice capabilities DPCD register from DSC sink to get + * the maximum slice count supported. This is used to populate + * the DSC parameters in the &struct drm_dsc_config by the driver. + * Driver creates an infoframe using these parameters to populate + * &struct drm_dsc_pps_infoframe. These are sent to the sink using DSC + * infoframe using the helper function drm_dsc_pps_infoframe_pack() + * + * Returns: + * Maximum slice count supported by DSC sink or 0 its invalid */ u8 drm_dp_dsc_sink_max_slice_count(const u8 dsc_dpcd[DP_DSC_RECEIVER_CAP_SIZE], bool is_edp) @@ -1405,6 +1418,21 @@ u8 drm_dp_dsc_sink_max_slice_count(const u8 dsc_dpcd[DP_DSC_RECEIVER_CAP_SIZE], } EXPORT_SYMBOL(drm_dp_dsc_sink_max_slice_count);
+/** + * drm_dp_dsc_sink_line_buf_depth() - Get the line buffer depth in bits + * @dsc_dpcd: DSC capabilities from DPCD + * + * Read the DSC DPCD register to parse the line buffer depth in bits which is + * number of bits of precision within the decoder line buffer supported by + * the DSC sink. This is used to populate the DSC parameters in the + * &struct drm_dsc_config by the driver. + * Driver creates an infoframe using these parameters to populate + * &struct drm_dsc_pps_infoframe. These are sent to the sink using DSC + * infoframe using the helper function drm_dsc_pps_infoframe_pack() + * + * Returns: + * Line buffer depth supported by DSC panel or 0 its invalid + */ u8 drm_dp_dsc_sink_line_buf_depth(const u8 dsc_dpcd[DP_DSC_RECEIVER_CAP_SIZE]) { u8 line_buf_depth = dsc_dpcd[DP_DSC_LINE_BUF_BIT_DEPTH - DP_DSC_SUPPORT]; @@ -1434,6 +1462,23 @@ u8 drm_dp_dsc_sink_line_buf_depth(const u8 dsc_dpcd[DP_DSC_RECEIVER_CAP_SIZE]) } EXPORT_SYMBOL(drm_dp_dsc_sink_line_buf_depth);
+/** + * drm_dp_dsc_sink_supported_input_bpcs() - Get all the input bits per component + * values supported by the DSC sink. + * @dsc_dpcd: DSC capabilities from DPCD + * @dsc_bpc: An array to be filled by this helper with supported + * input bpcs. + * + * Read the DSC DPCD from the sink device to parse the supported bits per + * component values. This is used to populate the DSC parameters + * in the &struct drm_dsc_config by the driver. + * Driver creates an infoframe using these parameters to populate + * &struct drm_dsc_pps_infoframe. These are sent to the sink using DSC + * infoframe using the helper function drm_dsc_pps_infoframe_pack() + * + * Returns: + * Number of input BPC values parsed from the DPCD + */ int drm_dp_dsc_sink_supported_input_bpcs(const u8 dsc_dpcd[DP_DSC_RECEIVER_CAP_SIZE], u8 dsc_bpc[3]) { diff --git a/drivers/gpu/drm/drm_dsc.c b/drivers/gpu/drm/drm_dsc.c index bc2b23adb072..bce99f95c1a3 100644 --- a/drivers/gpu/drm/drm_dsc.c +++ b/drivers/gpu/drm/drm_dsc.c @@ -17,6 +17,12 @@ /** * DOC: dsc helpers * + * VESA specification for DP 1.4 adds a new feature called Display Stream + * Compression (DSC) used to compress the pixel bits before sending it on + * DP/eDP/MIPI DSI interface. DSC is required to be enabled so that the existing + * display interfaces can support high resolutions at higher frames rates uisng + * the maximum available link capacity of these interfaces. + * * 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. @@ -26,6 +32,13 @@ * 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 + * as defined in &struct drm_dsc_pps_infoframe + * + * DP 1.4 spec defines the secondary data packet for sending the + * picture parameter infoframes from the source to the sink. + * This function populates the pps header defined in + * &struct drm_dsc_pps_infoframe as per the header bytes defined + * in &struct dp_sdp_header. */ void drm_dsc_dp_pps_header_init(struct drm_dsc_pps_infoframe *pps_sdp) { @@ -38,15 +51,20 @@ 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 + * Secondary data packet for DSC Picture Parameter Set. This is defined + * by &struct drm_dsc_pps_infoframe * @dsc_cfg: - * DSC Configuration data filled by driver + * DSC Configuration data filled by driver as defined by + * &struct drm_dsc_config + * + * DSC source device sends a secondary data packet filled with all the + * picture parameter set (PPS) information required by the sink to decode + * the compressed frame. Driver 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. */ void drm_dsc_pps_infoframe_pack(struct drm_dsc_pps_infoframe *pps_sdp, const struct drm_dsc_config *dsc_cfg) diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h index 5db7fb8c8b50..2711cdfa0c13 100644 --- a/include/drm/drm_dp_helper.h +++ b/include/drm/drm_dp_helper.h @@ -1052,11 +1052,18 @@ int drm_dp_bw_code_to_link_rate(u8 link_bw); #define DP_SDP_VSC_EXT_CEA 0x21 /* DP 1.4 */ /* 0x80+ CEA-861 infoframe types */
+/** + * struct dp_sdp_header - DP secondary data packet header + * @HB0: Secondary Data Packet ID + * @HB1: Secondary Data Packet Type + * @HB2: Secondary Data Packet Specific header, Byte 0 + * @HB3: Secondary Data packet Specific header, Byte 1 + */ struct dp_sdp_header { - u8 HB0; /* Secondary Data Packet ID */ - u8 HB1; /* Secondary Data Packet Type */ - u8 HB2; /* Secondary Data Packet Specific header, Byte 0 */ - u8 HB3; /* Secondary Data packet Specific header, Byte 1 */ + u8 HB0; + u8 HB1; + u8 HB2; + u8 HB3; } __packed;
#define EDP_SDP_HEADER_REVISION_MASK 0x1F diff --git a/include/drm/drm_dsc.h b/include/drm/drm_dsc.h index d03f1b83421a..8c6a18079086 100644 --- a/include/drm/drm_dsc.h +++ b/include/drm/drm_dsc.h @@ -44,111 +44,224 @@ #define DSC_1_2_MAX_LINEBUF_DEPTH_VAL 0 #define DSC_1_1_MAX_LINEBUF_DEPTH_BITS 13
-/* Configuration for a single Rate Control model range */ +/** + * struct drm_dsc_rc_range_parameters - DSC Rate Control range parameters + * + * This defines different rate control parameters used by the DSC engine + * to compress the frame. + */ struct drm_dsc_rc_range_parameters { - /* Min Quantization Parameters allowed for this range */ + /** + * @range_min_qp: Min Quantization Parameters allowed for this range + */ u8 range_min_qp; - /* Max Quantization Parameters allowed for this range */ + /** + * @range_max_qp: Max Quantization Parameters allowed for this range + */ u8 range_max_qp; - /* Bits/group offset to apply to target for this group */ + /** + * @range_bpg_offset: Bits/group offset to apply to target for this + * group + */ u8 range_bpg_offset; };
+/** + * struct drm_dsc_config - Parameters required to configure DSC + * + * Driver populates this structure with all the parameters required + * to configure the display stream compression on the source. + */ struct drm_dsc_config { - /* Bits / component for previous reconstructed line buffer */ + /** + * @line_buf_depth: Bits / component for previous reconstructed line + * buffer + */ u8 line_buf_depth; - /* Bits per component to code (must be 8, 10, or 12) */ + /** + * @bits_per_component: Bits per component to code (8/10/12) + */ u8 bits_per_component; - /* - * Flag indicating to do RGB - YCoCg conversion - * and back (should be 1 for RGB input) + /** + * @convert_rgb: Flag to indicate if RGB - YCoCg conversion is needed + * True if RGB input, False if YCoCg input */ bool convert_rgb; + /** + * @slice_count: Number fo slices per line used by the DSC encoder + */ u8 slice_count; - /* Slice Width */ + /** + * @slice_width: Width of each slice in pixels + */ u16 slice_width; - /* Slice Height */ + /** + * @slice_height: Slice height in pixels + */ u16 slice_height; - /* - * 4:2:2 enable mode (from PPS, 4:2:2 conversion happens - * outside of DSC encode/decode algorithm) + /** + * @enable422: True for 4_2_2 sampling, false for 4_4_4 sampling */ bool enable422; - /* Picture Width */ + /** + * @pic_width: Width of the input display frame in pixels + */ u16 pic_width; - /* Picture Height */ + /** + * @pic_height: Vertical height of the input display frame + */ u16 pic_height; - /* Offset to bits/group used by RC to determine QP adjustment */ + /** + * @rc_tgt_offset_high: Offset to bits/group used by RC to determine QP + * adjustment + */ u8 rc_tgt_offset_high; - /* Offset to bits/group used by RC to determine QP adjustment */ + /** + * @rc_tgt_offset_low: Offset to bits/group used by RC to determine QP + * adjustment + */ u8 rc_tgt_offset_low; - /* Bits/pixel target << 4 (ie., 4 fractional bits) */ + /** + * @bits_per_pixel: Target bits per pixel with 4 fractional bits. + * bits_per_pixel << 4 + */ u16 bits_per_pixel; - /* - * Factor to determine if an edge is present based - * on the bits produced + /** + * @rc_edge_factor: Factor to determine if an edge is present based on the + * bits produced */ u8 rc_edge_factor; - /* Slow down incrementing once the range reaches this value */ + /** + * @rc_quant_incr_limit1: Slow down incrementing once the range reaches this + * value + */ u8 rc_quant_incr_limit1; - /* Slow down incrementing once the range reaches this value */ + /** + * @rc_quant_incr_limit0: Slow down incrementing once the range reaches this + * value + */ u8 rc_quant_incr_limit0; - /* Number of pixels to delay the initial transmission */ + /** + * @initial_xmit_delay: Number of pixels to delay the initial transmission + */ u16 initial_xmit_delay; - /* Number of pixels to delay the VLD on the decoder,not including SSM */ + /** + * @initial_dec_delay: Initial decoder delay, number of pixel times that the + * decoer accumulates data in its rate buffer before + * starting to decode and output pixels. + */ u16 initial_dec_delay; - /* Block prediction enable */ + /** + * @block_pred_enable: True if block prediction is used to code any groups + * within the picture. + * False if BP not used + */ bool block_pred_enable; - /* Bits/group offset to use for first line of the slice */ + /** + * @first_line_bpg_offset: Number of additional bits allocated for each group on + * the first line of slice. + */ u8 first_line_bpg_offset; - /* Value to use for RC model offset at slice start */ + /** + * @initial_offset: Value to use for RC model offset at slice start + */ u16 initial_offset; - /* Thresholds defining each of the buffer ranges */ + /** + * @rc_buf_thresh: Thresholds defining each of the buffer ranges + */ u16 rc_buf_thresh[DSC_NUM_BUF_RANGES - 1]; - /* Parameters for each of the RC ranges */ + /** + * @rc_range_params: Parameters for each of the RC ranges defined in + * &struct drm_dsc_rc_range_parameters + */ struct drm_dsc_rc_range_parameters rc_range_params[DSC_NUM_BUF_RANGES]; - /* Total size of RC model */ + /** + * @rc_model_size: Total size of RC model + */ u16 rc_model_size; - /* Minimum QP where flatness information is sent */ + /** + * @flatness_min_qp: Minimum QP where flatness information is sent + */ u8 flatness_min_qp; - /* Maximum QP where flatness information is sent */ + /** + * @flatness_max_qp: Maximum QP where flatness information is sent + */ u8 flatness_max_qp; - /* Initial value for scale factor */ + /** + * @initial_scale_value: Initial value for the scale factor + */ u8 initial_scale_value; - /* Decrement scale factor every scale_decrement_interval groups */ + /** + * @scale_decrement_interval: Specifies number of group times between + * decrementing the scale factor at beginning + * of a slice. + */ u16 scale_decrement_interval; - /* Increment scale factor every scale_increment_interval groups */ + /** + * @scale_increment_interval: Number of group times between incrementing + * the scale factor value used at the beginning + * of a slice. + */ u16 scale_increment_interval; - /* Non-first line BPG offset to use */ + /** + * @nfl_bpg_offset: Non first line BPG offset to be used + */ u16 nfl_bpg_offset; - /* BPG offset used to enforce slice bit */ + /** + * @slice_bpg_offset: BPG offset used to enforce slice bit + */ u16 slice_bpg_offset; - /* Final RC linear transformation offset value */ + /** + * @final_offset: Final RC linear transformation offset value + */ u16 final_offset; - /* Enable on-off VBR (ie., disable stuffing bits) */ + /** + * @vbr_enable: True if VBR mode is enabled, false if disabled + */ bool vbr_enable; - /* Mux word size (in bits) for SSM mode */ + /** + * @mux_word_size: Mux word size (in bits) for SSM mode + */ u8 mux_word_size; - /* - * The (max) size in bytes of the "chunks" that are - * used in slice multiplexing + /** + * @slice_chunk_size: The (max) size in bytes of the "chunks" that are + * used in slice multiplexing. */ u16 slice_chunk_size; - /* Rate Control buffer siz in bits */ + /** + * @rc_bits: Rate control buffer size in bits + */ u16 rc_bits; - /* DSC Minor Version */ + /** + * @dsc_version_minor: DSC minor version + */ u8 dsc_version_minor; - /* DSC Major version */ + /** + * @dsc_version_major: DSC major version + */ u8 dsc_version_major; - /* Native 4:2:2 support */ + /** + * @native_422: True if Native 4:2:2 supported, else false + */ bool native_422; - /* Native 4:2:0 support */ + /** + * @native_420: True if Native 4:2:0 supported else false. + */ bool native_420; - /* Additional bits/grp for seconnd line of slice for native 4:2:0 */ + /** + * @second_line_bpg_offset: Additional bits/grp for seconnd line of slice for + * native 4:2:0 + */ u8 second_line_bpg_offset; - /* Num of bits deallocated for each grp that is not in second line of slice */ + /** + * @nsl_bpg_offset: Num of bits deallocated for each grp that is not in second + * line of slice + */ u16 nsl_bpg_offset; - /* Offset adj fr second line in Native 4:2:0 mode */ + /** + * @second_line_offset_adj: Offset adjustment for second line in Native 4:2:0 + * mode + */ u16 second_line_offset_adj; };
@@ -468,10 +581,13 @@ struct drm_dsc_picture_parameter_set { * This structure represents the DSC PPS infoframe required to send the Picture * Parameter Set metadata required before enabling VESA Display Stream * Compression. This is based on the DP Secondary Data Packet structure and - * comprises of SDP Header as defined in drm_dp_helper.h and PPS payload. + * comprises of SDP Header as defined &struct struct dp_sdp_header in drm_dp_helper.h + * and PPS payload defined in &struct drm_dsc_picture_parameter_set. * - * @pps_header: Header for PPS as per DP SDP header format + * @pps_header: Header for PPS as per DP SDP header format of type + * &struct dp_sdp_header * @pps_payload: PPS payload fields as per DSC specification Table 4-1 + * as represented in &struct drm_dsc_picture_parameter_set */ struct drm_dsc_pps_infoframe { struct dp_sdp_header pps_header;