drivers/gpu/drm/vkms/vkms_composer.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2
   3 #include <linux/crc32.h>
   4
   5 #include <drm/drm_atomic.h>
   6 #include <drm/drm_atomic_helper.h>
   7 #include <drm/drm_blend.h>
   8 #include <drm/drm_fourcc.h>
   9 #include <drm/drm_fixed.h>
  10 #include <drm/drm_gem_framebuffer_helper.h>
  11 #include <drm/drm_vblank.h>
  12 #include <linux/minmax.h>
  13
  14 #include "vkms_drv.h"
  15
  16 static u16 pre_mul_blend_channel(u16 src, u16 dst, u16 alpha)
  17 {
  18         u32 new_color;
  19
  20         new_color = (src * 0xffff + dst * (0xffff - alpha));
  21
  22         return DIV_ROUND_CLOSEST(new_color, 0xffff);
  23 }
  24
  25 /**
  26  * pre_mul_alpha_blend - alpha blending equation
  27  * @frame_info: Source framebuffer's metadata
  28  * @stage_buffer: The line with the pixels from src_plane
  29  * @output_buffer: A line buffer that receives all the blends output
  30  *
  31  * Using the information from the `frame_info`, this blends only the
  32  * necessary pixels from the `stage_buffer` to the `output_buffer`
  33  * using premultiplied blend formula.
  34  *
  35  * The current DRM assumption is that pixel color values have been already
  36  * pre-multiplied with the alpha channel values. See more
  37  * drm_plane_create_blend_mode_property(). Also, this formula assumes a
  38  * completely opaque background.
  39  */
  40 static void pre_mul_alpha_blend(struct vkms_frame_info *frame_info,
  41                                 struct line_buffer *stage_buffer,
  42                                 struct line_buffer *output_buffer)
  43 {
  44         int x_dst = frame_info->dst.x1;
  45         struct pixel_argb_u16 *out = output_buffer->pixels + x_dst;
  46         struct pixel_argb_u16 *in = stage_buffer->pixels;
  47         int x_limit = min_t(size_t, drm_rect_width(&frame_info->dst),
  48                             stage_buffer->n_pixels);
  49
  50         for (int x = 0; x < x_limit; x++) {
  51                 out[x].a = (u16)0xffff;
  52                 out[x].r = pre_mul_blend_channel(in[x].r, out[x].r, in[x].a);
  53                 out[x].g = pre_mul_blend_channel(in[x].g, out[x].g, in[x].a);
  54                 out[x].b = pre_mul_blend_channel(in[x].b, out[x].b, in[x].a);
  55         }
  56 }
  57
  58 static int get_y_pos(struct vkms_frame_info *frame_info, int y)
  59 {
  60         if (frame_info->rotation & DRM_MODE_REFLECT_Y)
  61                 return drm_rect_height(&frame_info->rotated) - y - 1;
  62
  63         switch (frame_info->rotation & DRM_MODE_ROTATE_MASK) {
  64         case DRM_MODE_ROTATE_90:
  65                 return frame_info->rotated.x2 - y - 1;
  66         case DRM_MODE_ROTATE_270:
  67                 return y + frame_info->rotated.x1;
  68         default:
  69                 return y;
  70         }
  71 }
  72
  73 static bool check_limit(struct vkms_frame_info *frame_info, int pos)
  74 {
  75         if (drm_rotation_90_or_270(frame_info->rotation)) {
  76                 if (pos >= 0 && pos < drm_rect_width(&frame_info->rotated))
  77                         return true;
  78         } else {
  79                 if (pos >= frame_info->rotated.y1 && pos < frame_info->rotated.y2)
  80                         return true;
  81         }
  82
  83         return false;
  84 }
  85
  86 static void fill_background(const struct pixel_argb_u16 *background_color,
  87                             struct line_buffer *output_buffer)
  88 {
  89         for (size_t i = 0; i < output_buffer->n_pixels; i++)
  90                 output_buffer->pixels[i] = *background_color;
  91 }
  92
  93 // lerp(a, b, t) = a + (b - a) * t
  94 static u16 lerp_u16(u16 a, u16 b, s64 t)
  95 {
  96         s64 a_fp = drm_int2fixp(a);
  97         s64 b_fp = drm_int2fixp(b);
  98
  99         s64 delta = drm_fixp_mul(b_fp - a_fp,  t);
 100
 101         return drm_fixp2int(a_fp + delta);
 102 }
 103
 104 static s64 get_lut_index(const struct vkms_color_lut *lut, u16 channel_value)
 105 {
 106         s64 color_channel_fp = drm_int2fixp(channel_value);
 107
 108         return drm_fixp_mul(color_channel_fp, lut->channel_value2index_ratio);
 109 }
 110
 111 /*
 112  * This enum is related to the positions of the variables inside
 113  * `struct drm_color_lut`, so the order of both needs to be the same.
 114  */
 115 enum lut_channel {
 116         LUT_RED = 0,
 117         LUT_GREEN,
 118         LUT_BLUE,
 119         LUT_RESERVED
 120 };
 121
 122 static u16 apply_lut_to_channel_value(const struct vkms_color_lut *lut, u16 channel_value,
 123                                       enum lut_channel channel)
 124 {
 125         s64 lut_index = get_lut_index(lut, channel_value);
 126
 127         /*
 128          * This checks if `struct drm_color_lut` has any gap added by the compiler
 129          * between the struct fields.
 130          */
 131         static_assert(sizeof(struct drm_color_lut) == sizeof(__u16) * 4);
 132
 133         u16 *floor_lut_value = (__u16 *)&lut->base[drm_fixp2int(lut_index)];
 134         u16 *ceil_lut_value = (__u16 *)&lut->base[drm_fixp2int_ceil(lut_index)];
 135
 136         u16 floor_channel_value = floor_lut_value[channel];
 137         u16 ceil_channel_value = ceil_lut_value[channel];
 138
 139         return lerp_u16(floor_channel_value, ceil_channel_value,
 140                         lut_index & DRM_FIXED_DECIMAL_MASK);
 141 }
 142
 143 static void apply_lut(const struct vkms_crtc_state *crtc_state, struct line_buffer *output_buffer)
 144 {
 145         if (!crtc_state->gamma_lut.base)
 146                 return;
 147
 148         if (!crtc_state->gamma_lut.lut_length)
 149                 return;
 150
 151         for (size_t x = 0; x < output_buffer->n_pixels; x++) {
 152                 struct pixel_argb_u16 *pixel = &output_buffer->pixels[x];
 153
 154                 pixel->r = apply_lut_to_channel_value(&crtc_state->gamma_lut, pixel->r, LUT_RED);
 155                 pixel->g = apply_lut_to_channel_value(&crtc_state->gamma_lut, pixel->g, LUT_GREEN);
 156                 pixel->b = apply_lut_to_channel_value(&crtc_state->gamma_lut, pixel->b, LUT_BLUE);
 157         }
 158 }
 159
 160 /**
 161  * blend - blend the pixels from all planes and compute crc
 162  * @wb: The writeback frame buffer metadata
 163  * @crtc_state: The crtc state
 164  * @crc32: The crc output of the final frame
 165  * @output_buffer: A buffer of a row that will receive the result of the blend(s)
 166  * @stage_buffer: The line with the pixels from plane being blend to the output
 167  * @row_size: The size, in bytes, of a single row
 168  *
 169  * This function blends the pixels (Using the `pre_mul_alpha_blend`)
 170  * from all planes, calculates the crc32 of the output from the former step,
 171  * and, if necessary, convert and store the output to the writeback buffer.
 172  */
 173 static void blend(struct vkms_writeback_job *wb,
 174                   struct vkms_crtc_state *crtc_state,
 175                   u32 *crc32, struct line_buffer *stage_buffer,
 176                   struct line_buffer *output_buffer, size_t row_size)
 177 {
 178         struct vkms_plane_state **plane = crtc_state->active_planes;
 179         u32 n_active_planes = crtc_state->num_active_planes;
 180         int y_pos;
 181
 182         const struct pixel_argb_u16 background_color = { .a = 0xffff };
 183
 184         size_t crtc_y_limit = crtc_state->base.crtc->mode.vdisplay;
 185
 186         for (size_t y = 0; y < crtc_y_limit; y++) {
 187                 fill_background(&background_color, output_buffer);
 188
 189                 /* The active planes are composed associatively in z-order. */
 190                 for (size_t i = 0; i < n_active_planes; i++) {
 191                         y_pos = get_y_pos(plane[i]->frame_info, y);
 192
 193                         if (!check_limit(plane[i]->frame_info, y_pos))
 194                                 continue;
 195
 196                         vkms_compose_row(stage_buffer, plane[i], y_pos);
 197                         pre_mul_alpha_blend(plane[i]->frame_info, stage_buffer,
 198                                             output_buffer);
 199                 }
 200
 201                 apply_lut(crtc_state, output_buffer);
 202
 203                 *crc32 = crc32_le(*crc32, (void *)output_buffer->pixels, row_size);
 204
 205                 if (wb)
 206                         vkms_writeback_row(wb, output_buffer, y_pos);
 207         }
 208 }
 209
 210 static int check_format_funcs(struct vkms_crtc_state *crtc_state,
 211                               struct vkms_writeback_job *active_wb)
 212 {
 213         struct vkms_plane_state **planes = crtc_state->active_planes;
 214         u32 n_active_planes = crtc_state->num_active_planes;
 215
 216         for (size_t i = 0; i < n_active_planes; i++)
 217                 if (!planes[i]->pixel_read)
 218                         return -1;
 219
 220         if (active_wb && !active_wb->pixel_write)
 221                 return -1;
 222
 223         return 0;
 224 }
 225
 226 static int check_iosys_map(struct vkms_crtc_state *crtc_state)
 227 {
 228         struct vkms_plane_state **plane_state = crtc_state->active_planes;
 229         u32 n_active_planes = crtc_state->num_active_planes;
 230
 231         for (size_t i = 0; i < n_active_planes; i++)
 232                 if (iosys_map_is_null(&plane_state[i]->frame_info->map[0]))
 233                         return -1;
 234
 235         return 0;
 236 }
 237
 238 static int compose_active_planes(struct vkms_writeback_job *active_wb,
 239                                  struct vkms_crtc_state *crtc_state,
 240                                  u32 *crc32)
 241 {
 242         size_t line_width, pixel_size = sizeof(struct pixel_argb_u16);
 243         struct line_buffer output_buffer, stage_buffer;
 244         int ret = 0;
 245
 246         /*
 247          * This check exists so we can call `crc32_le` for the entire line
 248          * instead doing it for each channel of each pixel in case
 249          * `struct `pixel_argb_u16` had any gap added by the compiler
 250          * between the struct fields.
 251          */
 252         static_assert(sizeof(struct pixel_argb_u16) == 8);
 253
 254         if (WARN_ON(check_iosys_map(crtc_state)))
 255                 return -EINVAL;
 256
 257         if (WARN_ON(check_format_funcs(crtc_state, active_wb)))
 258                 return -EINVAL;
 259
 260         line_width = crtc_state->base.crtc->mode.hdisplay;
 261         stage_buffer.n_pixels = line_width;
 262         output_buffer.n_pixels = line_width;
 263
 264         stage_buffer.pixels = kvmalloc(line_width * pixel_size, GFP_KERNEL);
 265         if (!stage_buffer.pixels) {
 266                 DRM_ERROR("Cannot allocate memory for the output line buffer");
 267                 return -ENOMEM;
 268         }
 269
 270         output_buffer.pixels = kvmalloc(line_width * pixel_size, GFP_KERNEL);
 271         if (!output_buffer.pixels) {
 272                 DRM_ERROR("Cannot allocate memory for intermediate line buffer");
 273                 ret = -ENOMEM;
 274                 goto free_stage_buffer;
 275         }
 276
 277         blend(active_wb, crtc_state, crc32, &stage_buffer,
 278               &output_buffer, line_width * pixel_size);
 279
 280         kvfree(output_buffer.pixels);
 281 free_stage_buffer:
 282         kvfree(stage_buffer.pixels);
 283
 284         return ret;
 285 }
 286
 287 /**
 288  * vkms_composer_worker - ordered work_struct to compute CRC
 289  *
 290  * @work: work_struct
 291  *
 292  * Work handler for composing and computing CRCs. work_struct scheduled in
 293  * an ordered workqueue that's periodically scheduled to run by
 294  * vkms_vblank_simulate() and flushed at vkms_atomic_commit_tail().
 295  */
 296 void vkms_composer_worker(struct work_struct *work)
 297 {
 298         struct vkms_crtc_state *crtc_state = container_of(work,
 299                                                 struct vkms_crtc_state,
 300                                                 composer_work);
 301         struct drm_crtc *crtc = crtc_state->base.crtc;
 302         struct vkms_writeback_job *active_wb = crtc_state->active_writeback;
 303         struct vkms_output *out = drm_crtc_to_vkms_output(crtc);
 304         bool crc_pending, wb_pending;
 305         u64 frame_start, frame_end;
 306         u32 crc32 = 0;
 307         int ret;
 308
 309         spin_lock_irq(&out->composer_lock);
 310         frame_start = crtc_state->frame_start;
 311         frame_end = crtc_state->frame_end;
 312         crc_pending = crtc_state->crc_pending;
 313         wb_pending = crtc_state->wb_pending;
 314         crtc_state->frame_start = 0;
 315         crtc_state->frame_end = 0;
 316         crtc_state->crc_pending = false;
 317
 318         if (crtc->state->gamma_lut) {
 319                 s64 max_lut_index_fp;
 320                 s64 u16_max_fp = drm_int2fixp(0xffff);
 321
 322                 crtc_state->gamma_lut.base = (struct drm_color_lut *)crtc->state->gamma_lut->data;
 323                 crtc_state->gamma_lut.lut_length =
 324                         crtc->state->gamma_lut->length / sizeof(struct drm_color_lut);
 325                 max_lut_index_fp = drm_int2fixp(crtc_state->gamma_lut.lut_length  - 1);
 326                 crtc_state->gamma_lut.channel_value2index_ratio = drm_fixp_div(max_lut_index_fp,
 327                                                                                u16_max_fp);
 328
 329         } else {
 330                 crtc_state->gamma_lut.base = NULL;
 331         }
 332
 333         spin_unlock_irq(&out->composer_lock);
 334
 335         /*
 336          * We raced with the vblank hrtimer and previous work already computed
 337          * the crc, nothing to do.
 338          */
 339         if (!crc_pending)
 340                 return;
 341
 342         if (wb_pending)
 343                 ret = compose_active_planes(active_wb, crtc_state, &crc32);
 344         else
 345                 ret = compose_active_planes(NULL, crtc_state, &crc32);
 346
 347         if (ret)
 348                 return;
 349
 350         if (wb_pending) {
 351                 drm_writeback_signal_completion(&out->wb_connector, 0);
 352                 spin_lock_irq(&out->composer_lock);
 353                 crtc_state->wb_pending = false;
 354                 spin_unlock_irq(&out->composer_lock);
 355         }
 356
 357         /*
 358          * The worker can fall behind the vblank hrtimer, make sure we catch up.
 359          */
 360         while (frame_start <= frame_end)
 361                 drm_crtc_add_crc_entry(crtc, true, frame_start++, &crc32);
 362 }
 363
 364 static const char * const pipe_crc_sources[] = {"auto"};
 365
 366 const char *const *vkms_get_crc_sources(struct drm_crtc *crtc,
 367                                         size_t *count)
 368 {
 369         *count = ARRAY_SIZE(pipe_crc_sources);
 370         return pipe_crc_sources;
 371 }
 372
 373 static int vkms_crc_parse_source(const char *src_name, bool *enabled)
 374 {
 375         int ret = 0;
 376
 377         if (!src_name) {
 378                 *enabled = false;
 379         } else if (strcmp(src_name, "auto") == 0) {
 380                 *enabled = true;
 381         } else {
 382                 *enabled = false;
 383                 ret = -EINVAL;
 384         }
 385
 386         return ret;
 387 }
 388
 389 int vkms_verify_crc_source(struct drm_crtc *crtc, const char *src_name,
 390                            size_t *values_cnt)
 391 {
 392         bool enabled;
 393
 394         if (vkms_crc_parse_source(src_name, &enabled) < 0) {
 395                 DRM_DEBUG_DRIVER("unknown source %s\n", src_name);
 396                 return -EINVAL;
 397         }
 398
 399         *values_cnt = 1;
 400
 401         return 0;
 402 }
 403
 404 void vkms_set_composer(struct vkms_output *out, bool enabled)
 405 {
 406         bool old_enabled;
 407
 408         if (enabled)
 409                 drm_crtc_vblank_get(&out->crtc);
 410
 411         spin_lock_irq(&out->lock);
 412         old_enabled = out->composer_enabled;
 413         out->composer_enabled = enabled;
 414         spin_unlock_irq(&out->lock);
 415
 416         if (old_enabled)
 417                 drm_crtc_vblank_put(&out->crtc);
 418 }
 419
 420 int vkms_set_crc_source(struct drm_crtc *crtc, const char *src_name)
 421 {
 422         struct vkms_output *out = drm_crtc_to_vkms_output(crtc);
 423         bool enabled = false;
 424         int ret = 0;
 425
 426         ret = vkms_crc_parse_source(src_name, &enabled);
 427
 428         vkms_set_composer(out, enabled);
 429
 430         return ret;
 431 }