Commit 05bad235 authored by Manasi Navare's avatar Manasi Navare

drm/dsc: Add kernel documentation for DRM DP DSC helpers

This patch adds appropriate 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.

v3:
* Fix the checkpatch warnings (Sean Paul)
v2:
* Add inline comments for longer structs (Daniel Vetter)
* Split the summary and description (Daniel Vetter)
Suggested-by: default avatarDaniel Vetter <daniel.vetter@intel.com>
Suggested-by: default avatarSean Paul <sean@poorly.run>
Cc: Daniel Vetter <daniel.vetter@intel.com>
Cc: Sean Paul <sean@poorly.run>
Signed-off-by: default avatarManasi Navare <manasi.d.navare@intel.com>
Acked-by: default avatarSean Paul <sean@poorly.run>
Reviewed-by: default avatarDaniel Vetter <daniel.vetter@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190206213148.21390-1-manasi.d.navare@intel.com
parent 05f8bc82
......@@ -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])
{
......
......@@ -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)
......
......@@ -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
......
......@@ -44,111 +44,231 @@
#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 per 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 decoder
* 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 +588,13 @@ 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;
......
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