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drm/vkms: Add documentation

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Add documentation around vkms_output and its initialization.
Add some documentation on pixel conversion functions.
Update of outdated comments for pixel_write functions.

Reviewed-by: José Expósito <jose.exposito89@gmail.com>
Signed-off-by: Louis Chauvet <louis.chauvet@bootlin.com>
Signed-off-by: Maíra Canal <mcanal@igalia.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240905-google-clarifications-v4-1-e43c1f2e3d87@bootlin.com
This commit is contained in:
Louis Chauvet
2024-09-05 15:27:06 +02:00
committed by Maíra Canal
parent 80fd814e93
commit 6e5eb6dcb3
4 changed files with 161 additions and 23 deletions
Download Patch File Download Diff File Expand all files Collapse all files

7
drivers/gpu/drm/vkms/vkms_composer.c
View File

@@ -189,6 +189,13 @@ static void blend(struct vkms_writeback_job *wb,
size_t crtc_y_limit = crtc_state->base.crtc->mode.vdisplay;
/*
* The planes are composed line-by-line to avoid heavy memory usage. It is a necessary
* complexity to avoid poor blending performance.
*
* The function vkms_compose_row() is used to read a line, pixel-by-pixel, into the staging
* buffer.
*/
for (size_t y = 0; y < crtc_y_limit; y++) {
fill_background(&background_color, output_buffer);

101
drivers/gpu/drm/vkms/vkms_drv.h
View File

@@ -25,6 +25,17 @@
#define VKMS_LUT_SIZE 256
/**
* struct vkms_frame_info - Structure to store the state of a frame
*
* @fb: backing drm framebuffer
* @src: source rectangle of this frame in the source framebuffer, stored in 16.16 fixed-point form
* @dst: destination rectangle in the crtc buffer, stored in whole pixel units
* @map: see @drm_shadow_plane_state.data
* @rotation: rotation applied to the source.
*
* @src and @dst should have the same size modulo the rotation.
*/
struct vkms_frame_info {
struct drm_framebuffer *fb;
struct drm_rect src, dst;
@@ -52,9 +63,11 @@ struct vkms_writeback_job {
};
/**
* vkms_plane_state - Driver specific plane state
* struct vkms_plane_state - Driver specific plane state
* @base: base plane state
* @frame_info: data required for composing computation
* @pixel_read: function to read a pixel in this plane. The creator of a struct vkms_plane_state
* must ensure that this pointer is valid
*/
struct vkms_plane_state {
struct drm_shadow_plane_state base;
@@ -73,29 +86,56 @@ struct vkms_color_lut {
};
/**
* vkms_crtc_state - Driver specific CRTC state
* struct vkms_crtc_state - Driver specific CRTC state
*
* @base: base CRTC state
* @composer_work: work struct to compose and add CRC entries
* @n_frame_start: start frame number for computed CRC
* @n_frame_end: end frame number for computed CRC
*
* @num_active_planes: Number of active planes
* @active_planes: List containing all the active planes (counted by
* @num_active_planes). They should be stored in z-order.
* @active_writeback: Current active writeback job
* @gamma_lut: Look up table for gamma used in this CRTC
* @crc_pending: Protected by @vkms_output.composer_lock, true when the frame CRC is not computed
* yet. Used by vblank to detect if the composer is too slow.
* @wb_pending: Protected by @vkms_output.composer_lock, true when a writeback frame is requested.
* @frame_start: Protected by @vkms_output.composer_lock, saves the frame number before the start
* of the composition process.
* @frame_end: Protected by @vkms_output.composer_lock, saves the last requested frame number.
* This is used to generate enough CRC entries when the composition worker is too slow.
*/
struct vkms_crtc_state {
struct drm_crtc_state base;
struct work_struct composer_work;
int num_active_planes;
/* stack of active planes for crc computation, should be in z order */
struct vkms_plane_state **active_planes;
struct vkms_writeback_job *active_writeback;
struct vkms_color_lut gamma_lut;
/* below four are protected by vkms_output.composer_lock */
bool crc_pending;
bool wb_pending;
u64 frame_start;
u64 frame_end;
};
/**
* struct vkms_output - Internal representation of all output components in VKMS
*
* @crtc: Base CRTC in DRM
* @encoder: DRM encoder used for this output
* @connector: DRM connector used for this output
* @wb_connecter: DRM writeback connector used for this output
* @vblank_hrtimer: Timer used to trigger the vblank
* @period_ns: vblank period, in nanoseconds, used to configure @vblank_hrtimer and to compute
* vblank timestamps
* @composer_workq: Ordered workqueue for @composer_state.composer_work.
* @lock: Lock used to protect concurrent access to the composer
* @composer_enabled: Protected by @lock, true when the VKMS composer is active (crc needed or
* writeback)
* @composer_state: Protected by @lock, current state of this VKMS output
* @composer_lock: Lock used internally to protect @composer_state members
*/
struct vkms_output {
struct drm_crtc crtc;
struct drm_encoder encoder;
@@ -103,28 +143,38 @@ struct vkms_output {
struct drm_writeback_connector wb_connector;
struct hrtimer vblank_hrtimer;
ktime_t period_ns;
/* ordered wq for composer_work */
struct workqueue_struct *composer_workq;
/* protects concurrent access to composer */
spinlock_t lock;
/* protected by @lock */
bool composer_enabled;
struct vkms_crtc_state *composer_state;
spinlock_t composer_lock;
};
struct vkms_device;
/**
* struct vkms_config - General configuration for VKMS driver
*
* @writeback: If true, a writeback buffer can be attached to the CRTC
* @cursor: If true, a cursor plane is created in the VKMS device
* @overlay: If true, NUM_OVERLAY_PLANES will be created for the VKMS device
* @dev: Used to store the current VKMS device. Only set when the device is instantiated.
*/
struct vkms_config {
bool writeback;
bool cursor;
bool overlay;
/* only set when instantiated */
struct vkms_device *dev;
};
/**
* struct vkms_device - Description of a VKMS device
*
* @drm - Base device in DRM
* @platform - Associated platform device
* @output - Configuration and sub-components of the VKMS device
* @config: Configuration used in this VKMS device
*/
struct vkms_device {
struct drm_device drm;
struct platform_device *platform;
@@ -132,6 +182,10 @@ struct vkms_device {
const struct vkms_config *config;
};
/*
* The following helpers are used to convert a member of a struct into its parent.
*/
#define drm_crtc_to_vkms_output(target) \
container_of(target, struct vkms_output, crtc)
@@ -144,12 +198,33 @@ struct vkms_device {
#define to_vkms_plane_state(target)\
container_of(target, struct vkms_plane_state, base.base)
/* CRTC */
/**
* vkms_crtc_init() - Initialize a CRTC for VKMS
* @dev: DRM device associated with the VKMS buffer
* @crtc: uninitialized CRTC device
* @primary: primary plane to attach to the CRTC
* @cursor: plane to attach to the CRTC
*/
int vkms_crtc_init(struct drm_device *dev, struct drm_crtc *crtc,
struct drm_plane *primary, struct drm_plane *cursor);
/**
* vkms_output_init() - Initialize all sub-components needed for a VKMS device.
*
* @vkmsdev: VKMS device to initialize
* @index: CRTC which can be attached to the planes. The caller must ensure that
* @index is positive and less or equals to 31.
*/
int vkms_output_init(struct vkms_device *vkmsdev, int index);
/**
* vkms_plane_init() - Initialize a plane
*
* @vkmsdev: VKMS device containing the plane
* @type: type of plane to initialize
* @index: CRTC which can be attached to the plane. The caller must ensure that
* @index is positive and less or equals to 31.
*/
struct vkms_plane *vkms_plane_init(struct vkms_device *vkmsdev,
enum drm_plane_type type, int index);

62
drivers/gpu/drm/vkms/vkms_formats.c
View File

@@ -9,24 +9,40 @@
#include "vkms_formats.h"
/**
* pixel_offset() - Get the offset of the pixel at coordinates x/y in the first plane
*
* @frame_info: Buffer metadata
* @x: The x coordinate of the wanted pixel in the buffer
* @y: The y coordinate of the wanted pixel in the buffer
*
* The caller must ensure that the framebuffer associated with this request uses a pixel format
* where block_h == block_w == 1.
* If this requirement is not fulfilled, the resulting offset can point to an other pixel or
* outside of the buffer.
*/
static size_t pixel_offset(const struct vkms_frame_info *frame_info, int x, int y)
{
return frame_info->offset + (y * frame_info->pitch)
+ (x * frame_info->cpp);
}
/*
* packed_pixels_addr - Get the pointer to pixel of a given pair of coordinates
/**
* packed_pixels_addr() - Get the pointer to the block containing the pixel at the given
* coordinates
*
* @frame_info: Buffer metadata
* @x: The x(width) coordinate of the 2D buffer
* @y: The y(Heigth) coordinate of the 2D buffer
* @x: The x (width) coordinate inside the plane
* @y: The y (height) coordinate inside the plane
*
* Takes the information stored in the frame_info, a pair of coordinates, and
* returns the address of the first color channel.
* This function assumes the channels are packed together, i.e. a color channel
* comes immediately after another in the memory. And therefore, this function
* doesn't work for YUV with chroma subsampling (e.g. YUV420 and NV21).
*
* The caller must ensure that the framebuffer associated with this request uses a pixel format
* where block_h == block_w == 1, otherwise the returned pointer can be outside the buffer.
*/
static void *packed_pixels_addr(const struct vkms_frame_info *frame_info,
int x, int y)
@@ -51,6 +67,13 @@ static int get_x_position(const struct vkms_frame_info *frame_info, int limit, i
return x;
}
/*
* The following functions take pixel data from the buffer and convert them to the format
* ARGB16161616 in @out_pixel.
*
* They are used in the vkms_compose_row() function to handle multiple formats.
*/
static void ARGB8888_to_argb_u16(u8 *src_pixels, struct pixel_argb_u16 *out_pixel)
{
/*
@@ -143,12 +166,11 @@ void vkms_compose_row(struct line_buffer *stage_buffer, struct vkms_plane_state
}
/*
* The following functions take an line of argb_u16 pixels from the
* src_buffer, convert them to a specific format, and store them in the
* destination.
* The following functions take one &struct pixel_argb_u16 and convert it to a specific format.
* The result is stored in @dst_pixels.
*
* They are used in the `compose_active_planes` to convert and store a line
* from the src_buffer to the writeback buffer.
* They are used in vkms_writeback_row() to convert and store a pixel from the src_buffer to
* the writeback buffer.
*/
static void argb_u16_to_ARGB8888(u8 *dst_pixels, struct pixel_argb_u16 *in_pixel)
{
@@ -214,6 +236,14 @@ static void argb_u16_to_RGB565(u8 *dst_pixels, struct pixel_argb_u16 *in_pixel)
*pixels = cpu_to_le16(r << 11 | g << 5 | b);
}
/**
* vkms_writeback_row() - Generic loop for all supported writeback format. It is executed just
* after the blending to write a line in the writeback buffer.
*
* @wb: Job where to insert the final image
* @src_buffer: Line to write
* @y: Row to write in the writeback buffer
*/
void vkms_writeback_row(struct vkms_writeback_job *wb,
const struct line_buffer *src_buffer, int y)
{
@@ -227,6 +257,13 @@ void vkms_writeback_row(struct vkms_writeback_job *wb,
wb->pixel_write(dst_pixels, &in_pixels[x]);
}
/**
* get_pixel_conversion_function() - Retrieve the correct read_pixel function for a specific
* format. The returned pointer is NULL for unsupported pixel formats. The caller must ensure that
* the pointer is valid before using it in a vkms_plane_state.
*
* @format: DRM_FORMAT_* value for which to obtain a conversion function (see [drm_fourcc.h])
*/
void *get_pixel_conversion_function(u32 format)
{
switch (format) {
@@ -245,6 +282,13 @@ void *get_pixel_conversion_function(u32 format)
}
}
/**
* get_pixel_write_function() - Retrieve the correct write_pixel function for a specific format.
* The returned pointer is NULL for unsupported pixel formats. The caller must ensure that the
* pointer is valid before using it in a vkms_writeback_job.
*
* @format: DRM_FORMAT_* value for which to obtain a conversion function (see [drm_fourcc.h])
*/
void *get_pixel_write_function(u32 format)
{
switch (format) {

14
drivers/gpu/drm/vkms/vkms_output.c
View File

@@ -21,6 +21,7 @@ static int vkms_conn_get_modes(struct drm_connector *connector)
{
int count;
/* Use the default modes list from DRM */
count = drm_add_modes_noedid(connector, XRES_MAX, YRES_MAX);
drm_set_preferred_mode(connector, XRES_DEF, YRES_DEF);
@@ -58,6 +59,12 @@ int vkms_output_init(struct vkms_device *vkmsdev, int index)
int writeback;
unsigned int n;
/*
* Initialize used plane. One primary plane is required to perform the composition.
*
* The overlay and cursor planes are not mandatory, but can be used to perform complex
* composition.
*/
primary = vkms_plane_init(vkmsdev, DRM_PLANE_TYPE_PRIMARY, index);
if (IS_ERR(primary))
return PTR_ERR(primary);
@@ -76,6 +83,7 @@ int vkms_output_init(struct vkms_device *vkmsdev, int index)
return PTR_ERR(cursor);
}
/* [1]: Allocation of a CRTC, its index will be BIT(0) = 1 */
ret = vkms_crtc_init(dev, crtc, &primary->base, &cursor->base);
if (ret)
return ret;
@@ -95,7 +103,11 @@ int vkms_output_init(struct vkms_device *vkmsdev, int index)
DRM_ERROR("Failed to init encoder\n");
goto err_encoder;
}
encoder->possible_crtcs = 1;
/*
* This is a hardcoded value to select crtc for the encoder.
* BIT(0) here designate the first registered CRTC, the one allocated in [1]
*/
encoder->possible_crtcs = BIT(0);
ret = drm_connector_attach_encoder(connector, encoder);
if (ret) {