---
This series does not introduce functionnal changes, only some
documentation and renaming to clarify the code.
---
Changes in v4:
- Applied comments from José
- Link to v3: https://lore.kernel.org/r/20240829-google-clarifications-v3-1-f6604e2f6297@xxxxxxxxxxx
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..672fe191e239 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
+ * @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);
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..0a5a185aa0b0 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 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) {
---
base-commit: 84addde447fd9d713e101437db0d4924855eff4f
change-id: 20240520-google-clarifications-dede8dcbe38a
Best regards,
