Add documentation around vkms_output and its initialization. Add some documentation on pixel conversion functions. Update of outdated comments for pixel_write functions. Signed-off-by: Louis Chauvet <louis.chauvet@xxxxxxxxxxx> --- This series does not introduce functionnal changes, only some documentation and renaming to clarify the code. --- Changes in v3: - Merged https://lore.kernel.org/all/20240802-yuv-v9-3-08a706669e16@xxxxxxxxxxx/ as it also add documentation - Apply José's comments, sorry - Replace =1 by =BIT(0) for possible_crtc value - Link to v2: https://lore.kernel.org/r/20240826-google-clarifications-v2-1-2574655b0b91@xxxxxxxxxxx Changes in v2: - Dropped already applied patches - Dropped useless patch as its content is deleted later - Remove dependency on previous series - Apply Maíra's comments - Link to v1: https://lore.kernel.org/r/20240814-google-clarifications-v1-0-3ee76d7d0c28@xxxxxxxxxxx --- drivers/gpu/drm/vkms/vkms_composer.c | 7 +++ drivers/gpu/drm/vkms/vkms_drv.h | 101 ++++++++++++++++++++++++++++++----- drivers/gpu/drm/vkms/vkms_formats.c | 62 +++++++++++++++++---- drivers/gpu/drm/vkms/vkms_output.c | 14 ++++- 4 files changed, 161 insertions(+), 23 deletions(-) diff --git a/drivers/gpu/drm/vkms/vkms_composer.c b/drivers/gpu/drm/vkms/vkms_composer.c index e7441b227b3c..57a5769fc994 100644 --- a/drivers/gpu/drm/vkms/vkms_composer.c +++ b/drivers/gpu/drm/vkms/vkms_composer.c @@ -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); diff --git a/drivers/gpu/drm/vkms/vkms_drv.h b/drivers/gpu/drm/vkms/vkms_drv.h index 5e46ea5b96dc..12a11976f2fc 100644 --- a/drivers/gpu/drm/vkms/vkms_drv.h +++ b/drivers/gpu/drm/vkms/vkms_drv.h @@ -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 + * @possible_crtc_index: CRTC which can be attached to the plane. The caller must ensure that + * possible_crtc_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); diff --git a/drivers/gpu/drm/vkms/vkms_formats.c b/drivers/gpu/drm/vkms/vkms_formats.c index 040b7f113a3b..e8a5cc235ebb 100644 --- a/drivers/gpu/drm/vkms/vkms_formats.c +++ b/drivers/gpu/drm/vkms/vkms_formats.c @@ -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) { diff --git a/drivers/gpu/drm/vkms/vkms_output.c b/drivers/gpu/drm/vkms/vkms_output.c index 5ce70dd946aa..56801e914208 100644 --- a/drivers/gpu/drm/vkms/vkms_output.c +++ b/drivers/gpu/drm/vkms/vkms_output.c @@ -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 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. + * 1 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) { --- base-commit: 84addde447fd9d713e101437db0d4924855eff4f change-id: 20240520-google-clarifications-dede8dcbe38a Best regards, -- Louis Chauvet <louis.chauvet@xxxxxxxxxxx>
