// SPDX-License-Identifier: GPL-2.0+
#include <linux/crc32.h>
#include <drm/drm_atomic.h>
#include <drm/drm_atomic_helper.h>
#include <drm/drm_blend.h>
#include <drm/drm_fourcc.h>
#include <drm/drm_fixed.h>
#include <drm/drm_gem_framebuffer_helper.h>
#include <drm/drm_vblank.h>
#include <linux/minmax.h>
#include "vkms_drv.h"
static u16 pre_mul_blend_channel(u16 src, u16 dst, u16 alpha)
{
u32 new_color;
new_color = (src * 0xffff + dst * (0xffff - alpha));
return DIV_ROUND_CLOSEST(new_color, 0xffff);
}
/**
* pre_mul_alpha_blend - alpha blending equation
* @stage_buffer: The line with the pixels from src_plane
* @output_buffer: A line buffer that receives all the blends output
* @x_start: The start offset
* @pixel_count: The number of pixels to blend
*
* The pixels [@x_start;@x_start+@pixel_count) in stage_buffer are blended at
* [@x_start;@x_start+@pixel_count) in output_buffer.
*
* The current DRM assumption is that pixel color values have been already
* pre-multiplied with the alpha channel values. See more
* drm_plane_create_blend_mode_property(). Also, this formula assumes a
* completely opaque background.
*/
static void pre_mul_alpha_blend(const struct line_buffer *stage_buffer,
struct line_buffer *output_buffer, int x_start, int pixel_count)
{
struct pixel_argb_u16 *out = &output_buffer->pixels[x_start];
const struct pixel_argb_u16 *in = &stage_buffer->pixels[x_start];
for (int i = 0; i < pixel_count; i++) {
out[i].a = (u16)0xffff;
out[i].r = pre_mul_blend_channel(in[i].r, out[i].r, in[i].a);
out[i].g = pre_mul_blend_channel(in[i].g, out[i].g, in[i].a);
out[i].b = pre_mul_blend_channel(in[i].b, out[i].b, in[i].a);
}
}
static void fill_background(const struct pixel_argb_u16 *background_color,
struct line_buffer *output_buffer)
{
for (size_t i = 0; i < output_buffer->n_pixels; i++)
output_buffer->pixels[i] = *background_color;
}
// lerp(a, b, t) = a + (b - a) * t
static u16 lerp_u16(u16 a, u16 b, s64 t)
{
s64 a_fp = drm_int2fixp(a);
s64 b_fp = drm_int2fixp(b);
s64 delta = drm_fixp_mul(b_fp - a_fp, t);
return drm_fixp2int_round(a_fp + delta);
}
static s64 get_lut_index(const struct vkms_color_lut *lut, u16 channel_value)
{
s64 color_channel_fp = drm_int2fixp(channel_value);
return drm_fixp_mul(color_channel_fp, lut->channel_value2index_ratio);
}
/*
* This enum is related to the positions of the variables inside
* `struct drm_color_lut`, so the order of both needs to be the same.
*/
enum lut_channel {
LUT_RED = 0,
LUT_GREEN,
LUT_BLUE,
LUT_RESERVED
};
static u16 apply_lut_to_channel_value(const struct vkms_color_lut *lut, u16 channel_value,
enum lut_channel channel)
{
s64 lut_index = get_lut_index(lut, channel_value);
u16 *floor_lut_value, *ceil_lut_value;
u16 floor_channel_value, ceil_channel_value;
/*
* This checks if `struct drm_color_lut` has any gap added by the compiler
* between the struct fields.
*/
static_assert(sizeof(struct drm_color_lut) == sizeof(__u16) * 4);
floor_lut_value = (__u16 *)&lut->base[drm_fixp2int(lut_index)];
if (drm_fixp2int(lut_index) == (lut->lut_length - 1))
/* We're at the end of the LUT array, use same value for ceil and floor */
ceil_lut_value = floor_lut_value;
else
ceil_lut_value = (__u16 *)&lut->base[drm_fixp2int_ceil(lut_index)];
floor_channel_value = floor_lut_value[channel];
ceil_channel_value = ceil_lut_value[channel];
return lerp_u16(floor_channel_value, ceil_channel_value,
lut_index & DRM_FIXED_DECIMAL_MASK);
}
static void apply_lut(const struct vkms_crtc_state *crtc_state, struct line_buffer *output_buffer)
{
if (!crtc_state->gamma_lut.base)
return;
if (!crtc_state->gamma_lut.lut_length)
return;
for (size_t x = 0; x < output_buffer->n_pixels; x++) {
struct pixel_argb_u16 *pixel = &output_buffer->pixels[x];
pixel->r = apply_lut_to_channel_value(&crtc_state->gamma_lut, pixel->r, LUT_RED);
pixel->g = apply_lut_to_channel_value(&crtc_state->gamma_lut, pixel->g, LUT_GREEN);
pixel->b = apply_lut_to_channel_value(&crtc_state->gamma_lut, pixel->b, LUT_BLUE);
}
}
/**
* direction_for_rotation() - Get the correct reading direction for a given rotation
*
* @rotation: Rotation to analyze. It correspond the field @frame_info.rotation.
*
* This function will use the @rotation setting of a source plane to compute the reading
* direction in this plane which correspond to a "left to right writing" in the CRTC.
* For example, if the buffer is reflected on X axis, the pixel must be read from right to left
* to be written from left to right on the CRTC.
*/
static enum pixel_read_direction direction_for_rotation(unsigned int rotation)
{
struct drm_rect tmp_a, tmp_b;
int x, y;
/*
* Points A and B are depicted as zero-size rectangles on the CRTC.
* The CRTC writing direction is from A to B. The plane reading direction
* is discovered by inverse-transforming A and B.
* The reading direction is computed by rotating the vector AB (top-left to top-right) in a
* 1x1 square.
*/
tmp_a = DRM_RECT_INIT(0, 0, 0, 0);
tmp_b = DRM_RECT_INIT(1, 0, 0, 0);
drm_rect_rotate_inv(&tmp_a, 1, 1, rotation);
drm_rect_rotate_inv(&tmp_b, 1, 1, rotation);
x = tmp_b.x1 - tmp_a.x1;
y = tmp_b.y1 - tmp_a.y1;
if (x == 1 && y == 0)
return READ_LEFT_TO_RIGHT;
else if (x == -1 && y == 0)
return READ_RIGHT_TO_LEFT;
else if (y == 1 && x == 0)
return READ_TOP_TO_BOTTOM;
else if (y == -1 && x == 0)
return READ_BOTTOM_TO_TOP;
WARN_ONCE(true, "The inverse of the rotation gives an incorrect direction.");
return READ_LEFT_TO_RIGHT;
}
/**
* clamp_line_coordinates() - Compute and clamp the coordinate to read and write during the blend
* process.
*
* @direction: direction of the reading
* @current_plane: current plane blended
* @src_line: source line of the reading. Only the top-left coordinate is used. This rectangle
* must be rotated and have a shape of 1*pixel_count if @direction is vertical and a shape of
* pixel_count*1 if @direction is horizontal.
* @src_x_start: x start coordinate for the line reading
* @src_y_start: y start coordinate for the line reading
* @dst_x_start: x coordinate to blend the read line
* @pixel_count: number of pixels to blend
*
* This function is mainly a safety net to avoid reading outside the source buffer. As the
* userspace should never ask to read outside the source plane, all the cases covered here should
* be dead code.
*/
static void clamp_line_coordinates(enum pixel_read_direction direction,
const struct vkms_plane_state *current_plane,
const struct drm_rect *src_line, int *src_x_start,
int *src_y_start, int *dst_x_start, int *pixel_count)
{
/* By default the start points are correct */
*src_x_start = src_line->x1;
*src_y_start = src_line->y1;
*dst_x_start = current_plane->frame_info->dst.x1;
/* Get the correct number of pixel to blend, it depends of the direction */
switch (direction) {
case READ_LEFT_TO_RIGHT:
case READ_RIGHT_TO_LEFT:
*pixel_count = drm_rect_width(src_line);
break;
case READ_BOTTOM_TO_TOP:
case READ_TOP_TO_BOTTOM:
*pixel_count = drm_rect_height(src_line);
break;
}
/*
* Clamp the coordinates to avoid reading outside the buffer
*
* This is mainly a security check to avoid reading outside the buffer, the userspace
* should never request to read outside the source buffer.
*/
switch (direction) {
case READ_LEFT_TO_RIGHT:
case READ_RIGHT_TO_LEFT:
if (*src_x_start < 0) {
*pixel_count += *src_x_start;
*dst_x_start -= *src_x_start;
*src_x_start = 0;
}
if (*src_x_start + *pixel_count > current_plane->frame_info->fb->width)
*pixel_count = max(0, (int)current_plane->frame_info->fb->width -
*src_x_start);
break;
case READ_BOTTOM_TO_TOP:
case READ_TOP_TO_BOTTOM:
if (*src_y_start < 0) {
*pixel_count += *src_y_start;
*dst_x_start -= *src_y_start;
*src_y_start = 0;
}
if (*src_y_start + *pixel_count > current_plane->frame_info->fb->height)
*pixel_count = max(0, (int)current_plane->frame_info->fb->height -
*src_y_start);
break;
}
}
/**
* blend_line() - Blend a line from a plane to the output buffer
*
* @current_plane: current plane to work on
* @y: line to write in the output buffer
* @crtc_x_limit: width of the output buffer
* @stage_buffer: temporary buffer to convert the pixel line from the source buffer
* @output_buffer: buffer to blend the read line into.
*/
static void blend_line(struct vkms_plane_state *current_plane, int y,
int crtc_x_limit, struct line_buffer *stage_buffer,
struct line_buffer *output_buffer)
{
int src_x_start, src_y_start, dst_x_start, pixel_count;
struct drm_rect dst_line, tmp_src, src_line;
/* Avoid rendering useless lines */
if (y < current_plane->frame_info->dst.y1 ||
y >= current_plane->frame_info->dst.y2)
return;
/*
* dst_line is the line to copy. The initial coordinates are inside the
* destination framebuffer, and then drm_rect_* helpers are used to
* compute the correct position into the source framebuffer.
*/
dst_line = DRM_RECT_INIT(current_plane->frame_info->dst.x1, y,
drm_rect_width(¤t_plane->frame_info->dst),
1);
drm_rect_fp_to_int(&tmp_src, ¤t_plane->frame_info->src);
/*
* [1]: Clamping src_line to the crtc_x_limit to avoid writing outside of
* the destination buffer
*/
dst_line.x1 = max_t(int, dst_line.x1, 0);
dst_line.x2 = min_t(int, dst_line.x2, crtc_x_limit);
/* The destination is completely outside of the crtc. */
if (dst_line.x2 <= dst_line.x1)
return;
src_line = dst_line;
/*
* Transform the coordinate x/y from the crtc to coordinates into
* coordinates for the src buffer.
*
* - Cancel the offset of the dst buffer.
* - Invert the rotation. This assumes that
* dst = drm_rect_rotate(src, rotation) (dst and src have the
* same size, but can be rotated).
* - Apply the offset of the source rectangle to the coordinate.
*/
drm_rect_translate(&src_line, -current_plane->frame_info->dst.x1,
-current_plane->frame_info->dst.y1);
drm_rect_rotate_inv(&src_line, drm_rect_width(&tmp_src),
drm_rect_height(&tmp_src),
current_plane->frame_info->rotation);
drm_rect_translate(&src_line, tmp_src.x1, tmp_src.y1);
/* Get the correct reading direction in the source buffer. */
enum pixel_read_direction direction =
direction_for_rotation(current_plane->frame_info->rotation);
/* [2]: Compute and clamp the number of pixel to read */
clamp_line_coordinates(direction, current_plane, &src_line, &src_x_start, &src_y_start,
&dst_x_start, &pixel_count);
if (pixel_count <= 0) {
/* Nothing to read, so avoid multiple function calls */
return;
}
/*
* Modify the starting point to take in account the rotation
*
* src_line is the top-left corner, so when reading READ_RIGHT_TO_LEFT or
* READ_BOTTOM_TO_TOP, it must be changed to the top-right/bottom-left
* corner.
*/
if (direction == READ_RIGHT_TO_LEFT) {
// src_x_start is now the right point
src_x_start += pixel_count - 1;
} else if (direction == READ_BOTTOM_TO_TOP) {
// src_y_start is now the bottom point
src_y_start += pixel_count - 1;
}
/*
* Perform the conversion and the blending
*
* Here we know that the read line (x_start, y_start, pixel_count) is
* inside the source buffer [2] and we don't write outside the stage
* buffer [1].
*/
current_plane->pixel_read_line(current_plane, src_x_start, src_y_start, direction,
pixel_count, &stage_buffer->pixels[dst_x_start]);
pre_mul_alpha_blend(stage_buffer, output_buffer,
dst_x_start, pixel_count);
}
/**
* blend - blend the pixels from all planes and compute crc
* @wb: The writeback frame buffer metadata
* @crtc_state: The crtc state
* @crc32: The crc output of the final frame
* @output_buffer: A buffer of a row that will receive the result of the blend(s)
* @stage_buffer: The line with the pixels from plane being blend to the output
* @row_size: The size, in bytes, of a single row
*
* This function blends the pixels (Using the `pre_mul_alpha_blend`)
* from all planes, calculates the crc32 of the output from the former step,
* and, if necessary, convert and store the output to the writeback buffer.
*/
static void blend(struct vkms_writeback_job *wb,
struct vkms_crtc_state *crtc_state,
u32 *crc32, struct line_buffer *stage_buffer,
struct line_buffer *output_buffer, size_t row_size)
{
struct vkms_plane_state **plane = crtc_state->active_planes;
u32 n_active_planes = crtc_state->num_active_planes;
const struct pixel_argb_u16 background_color = { .a = 0xffff };
int crtc_y_limit = crtc_state->base.mode.vdisplay;
int crtc_x_limit = crtc_state->base.mode.hdisplay;
/*
* The planes are composed line-by-line to avoid heavy memory usage. It is a necessary
* complexity to avoid poor blending performance.
*
* The function pixel_read_line callback is used to read a line, using an efficient
* algorithm for a specific format, into the staging buffer.
*/
for (int y = 0; y < crtc_y_limit; y++) {
fill_background(&background_color, output_buffer);
/* The active planes are composed associatively in z-order. */
for (size_t i = 0; i < n_active_planes; i++) {
blend_line(plane[i], y, crtc_x_limit, stage_buffer, output_buffer);
}
apply_lut(crtc_state, output_buffer);
*crc32 = crc32_le(*crc32, (void *)output_buffer->pixels, row_size);
if (wb)
vkms_writeback_row(wb, output_buffer, y);
}
}
static int check_format_funcs(struct vkms_crtc_state *crtc_state,
struct vkms_writeback_job *active_wb)
{
struct vkms_plane_state **planes = crtc_state->active_planes;
u32 n_active_planes = crtc_state->num_active_planes;
for (size_t i = 0; i < n_active_planes; i++)
if (!planes[i]->pixel_read_line)
return -1;
if (active_wb && !active_wb->pixel_write)
return -1;
return 0;
}
static int check_iosys_map(struct vkms_crtc_state *crtc_state)
{
struct vkms_plane_state **plane_state = crtc_state->active_planes;
u32 n_active_planes = crtc_state->num_active_planes;
for (size_t i = 0; i < n_active_planes; i++)
if (iosys_map_is_null(&plane_state[i]->frame_info->map[0]))
return -1;
return 0;
}
static int compose_active_planes(struct vkms_writeback_job *active_wb,
struct vkms_crtc_state *crtc_state,
u32 *crc32)
{
size_t line_width, pixel_size = sizeof(struct pixel_argb_u16);
struct line_buffer output_buffer, stage_buffer;
int ret = 0;
/*
* This check exists so we can call `crc32_le` for the entire line
* instead doing it for each channel of each pixel in case
* `struct `pixel_argb_u16` had any gap added by the compiler
* between the struct fields.
*/
static_assert(sizeof(struct pixel_argb_u16) == 8);
if (WARN_ON(check_iosys_map(crtc_state)))
return -EINVAL;
if (WARN_ON(check_format_funcs(crtc_state, active_wb)))
return -EINVAL;
line_width = crtc_state->base.mode.hdisplay;
stage_buffer.n_pixels = line_width;
output_buffer.n_pixels = line_width;
stage_buffer.pixels = kvmalloc(line_width * pixel_size, GFP_KERNEL);
if (!stage_buffer.pixels) {
DRM_ERROR("Cannot allocate memory for the output line buffer");
return -ENOMEM;
}
output_buffer.pixels = kvmalloc(line_width * pixel_size, GFP_KERNEL);
if (!output_buffer.pixels) {
DRM_ERROR("Cannot allocate memory for intermediate line buffer");
ret = -ENOMEM;
goto free_stage_buffer;
}
blend(active_wb, crtc_state, crc32, &stage_buffer,
&output_buffer, line_width * pixel_size);
kvfree(output_buffer.pixels);
free_stage_buffer:
kvfree(stage_buffer.pixels);
return ret;
}
/**
* vkms_composer_worker - ordered work_struct to compute CRC
*
* @work: work_struct
*
* Work handler for composing and computing CRCs. work_struct scheduled in
* an ordered workqueue that's periodically scheduled to run by
* vkms_vblank_simulate() and flushed at vkms_atomic_commit_tail().
*/
void vkms_composer_worker(struct work_struct *work)
{
struct vkms_crtc_state *crtc_state = container_of(work,
struct vkms_crtc_state,
composer_work);
struct drm_crtc *crtc = crtc_state->base.crtc;
struct vkms_writeback_job *active_wb = crtc_state->active_writeback;
struct vkms_output *out = drm_crtc_to_vkms_output(crtc);
bool crc_pending, wb_pending;
u64 frame_start, frame_end;
u32 crc32 = 0;
int ret;
spin_lock_irq(&out->composer_lock);
frame_start = crtc_state->frame_start;
frame_end = crtc_state->frame_end;
crc_pending = crtc_state->crc_pending;
wb_pending = crtc_state->wb_pending;
crtc_state->frame_start = 0;
crtc_state->frame_end = 0;
crtc_state->crc_pending = false;
if (crtc->state->gamma_lut) {
s64 max_lut_index_fp;
s64 u16_max_fp = drm_int2fixp(0xffff);
crtc_state->gamma_lut.base = (struct drm_color_lut *)crtc->state->gamma_lut->data;
crtc_state->gamma_lut.lut_length =
crtc->state->gamma_lut->length / sizeof(struct drm_color_lut);
max_lut_index_fp = drm_int2fixp(crtc_state->gamma_lut.lut_length - 1);
crtc_state->gamma_lut.channel_value2index_ratio = drm_fixp_div(max_lut_index_fp,
u16_max_fp);
} else {
crtc_state->gamma_lut.base = NULL;
}
spin_unlock_irq(&out->composer_lock);
/*
* We raced with the vblank hrtimer and previous work already computed
* the crc, nothing to do.
*/
if (!crc_pending)
return;
if (wb_pending)
ret = compose_active_planes(active_wb, crtc_state, &crc32);
else
ret = compose_active_planes(NULL, crtc_state, &crc32);
if (ret)
return;
if (wb_pending) {
drm_writeback_signal_completion(&out->wb_connector, 0);
spin_lock_irq(&out->composer_lock);
crtc_state->wb_pending = false;
spin_unlock_irq(&out->composer_lock);
}
/*
* The worker can fall behind the vblank hrtimer, make sure we catch up.
*/
while (frame_start <= frame_end)
drm_crtc_add_crc_entry(crtc, true, frame_start++, &crc32);
}
static const char *const pipe_crc_sources[] = { "auto" };
const char *const *vkms_get_crc_sources(struct drm_crtc *crtc,
size_t *count)
{
*count = ARRAY_SIZE(pipe_crc_sources);
return pipe_crc_sources;
}
static int vkms_crc_parse_source(const char *src_name, bool *enabled)
{
int ret = 0;
if (!src_name) {
*enabled = false;
} else if (strcmp(src_name, "auto") == 0) {
*enabled = true;
} else {
*enabled = false;
ret = -EINVAL;
}
return ret;
}
int vkms_verify_crc_source(struct drm_crtc *crtc, const char *src_name,
size_t *values_cnt)
{
bool enabled;
if (vkms_crc_parse_source(src_name, &enabled) < 0) {
DRM_DEBUG_DRIVER("unknown source %s\n", src_name);
return -EINVAL;
}
*values_cnt = 1;
return 0;
}
void vkms_set_composer(struct vkms_output *out, bool enabled)
{
bool old_enabled;
if (enabled)
drm_crtc_vblank_get(&out->crtc);
spin_lock_irq(&out->lock);
old_enabled = out->composer_enabled;
out->composer_enabled = enabled;
spin_unlock_irq(&out->lock);
if (old_enabled)
drm_crtc_vblank_put(&out->crtc);
}
int vkms_set_crc_source(struct drm_crtc *crtc, const char *src_name)
{
struct vkms_output *out = drm_crtc_to_vkms_output(crtc);
bool enabled = false;
int ret = 0;
ret = vkms_crc_parse_source(src_name, &enabled);
vkms_set_composer(out, enabled);
return ret;
}