src/gallium/drivers/panfrost/pan_blending.c

   1 /*
   2  * © Copyright 2018 Alyssa Rosenzweig
   3  *
   4  * Permission is hereby granted, free of charge, to any person obtaining a
   5  * copy of this software and associated documentation files (the "Software"),
   6  * to deal in the Software without restriction, including without limitation
   7  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
   8  * and/or sell copies of the Software, and to permit persons to whom the
   9  * Software is furnished to do so, subject to the following conditions:
  10  *
  11  * The above copyright notice and this permission notice (including the next
  12  * paragraph) shall be included in all copies or substantial portions of the
  13  * Software.
  14  *
  15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  16  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  18  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  19  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  20  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  21  * SOFTWARE.
  22  *
  23  */
  24
  25 #include <stdio.h>
  26 #include "pan_blending.h"
  27 #include "pan_context.h"
  28 #include "gallium/auxiliary/util/u_blend.h"
  29
  30 /*
  31  * Implements fixed-function blending on Midgard.
  32  *
  33  * Midgard splits blending into a fixed-function fast path and a programmable
  34  * slow path. The fixed function blending architecture is based on "dominant"
  35  * blend factors. Blending is encoded separately (but identically) between RGB
  36  * and alpha functions.
  37  *
  38  * Essentially, for a given blending operation, there is a single dominant
  39  * factor. The following dominant factors are possible:
  40  *
  41  *      - zero
  42  *      - source color
  43  *      - destination color
  44  *      - source alpha
  45  *      - destination alpha
  46  *      - constant float
  47  *
  48  * Further, a dominant factor's arithmetic compliment could be used. For
  49  * instance, to encode GL_ONE_MINUS_SOURCE_ALPHA, the dominant factor would be
  50  * MALI_DOMINANT_SRC_ALPHA with the complement_dominant bit set.
  51  *
  52  * A single constant float can be passed to the fixed-function hardware,
  53  * allowing CONSTANT_ALPHA support. Further, if all components of the constant
  54  * glBlendColor are identical, CONSTANT_COLOR can be implemented with the
  55  * constant float mode. If the components differ, programmable blending is
  56  * required.
  57  *
  58  * The nondominant factor can be either:
  59  *
  60  *      - the same as the dominant factor (MALI_BLEND_NON_MIRROR)
  61  *      - zero (MALI_BLEND_NON_ZERO)
  62  *
  63  * Exactly one of the blend operation's source or destination can be used as
  64  * the dominant factor; this is selected by the
  65  * MALI_BLEND_DOM_SOURCE/DESTINATION flag.
  66  *
  67  * By default, all blending follows the standard OpenGL addition equation:
  68  *
  69  *      out = source_value * source_factor + destination_value * destination_factor
  70  *
  71  * By setting the negate_source or negate_dest bits, other blend functions can
  72  * be created. For instance, for SUBTRACT mode, set the "negate destination"
  73  * flag, and similarly for REVERSE_SUBTRACT with "negate source".
  74  *
  75  * Finally, there is a "clip modifier" controlling the final blending
  76  * behaviour, allowing for the following modes:
  77  *
  78  *      - normal
  79  *      - force source factor to one (MALI_BLEND_MODE_SOURCE_ONE)
  80  *      - force destination factor to one (MALI_BLEND_MODE_DEST_ONE)
  81  *
  82  * The clipping flags can be used to encode blend modes where the nondominant
  83  * factor is ONE.
  84  *
  85  * As an example putting it all together, to encode the following blend state:
  86  *
  87  *      glBlendEquation(GL_FUNC_REVERSE_SUBTRACT);
  88  *      glBlendFunc(GL_ONE_MINUS_SRC_ALPHA, GL_ONE);
  89  *
  90  * We need the following configuration:
  91  *
  92  *      - negate source (for REVERSE_SUBTRACT)
  93  *      - dominant factor "source alpha"
  94  *              - complement dominant
  95  *              - source dominant
  96  *      - force destination to ONE
  97  *
  98  * The following routines implement this fixed function blending encoding
  99  */
 100
 101 /* Helper to find the uncomplemented Gallium blend factor corresponding to a
 102  * complemented Gallium blend factor */
 103
 104 static int
 105 complement_factor(int factor)
 106 {
 107         switch (factor) {
 108         case PIPE_BLENDFACTOR_INV_SRC_COLOR:
 109                 return PIPE_BLENDFACTOR_SRC_COLOR;
 110
 111         case PIPE_BLENDFACTOR_INV_SRC_ALPHA:
 112                 return PIPE_BLENDFACTOR_SRC_ALPHA;
 113
 114         case PIPE_BLENDFACTOR_INV_DST_ALPHA:
 115                 return PIPE_BLENDFACTOR_DST_ALPHA;
 116
 117         case PIPE_BLENDFACTOR_INV_DST_COLOR:
 118                 return PIPE_BLENDFACTOR_DST_COLOR;
 119
 120         case PIPE_BLENDFACTOR_INV_CONST_COLOR:
 121                 return PIPE_BLENDFACTOR_CONST_COLOR;
 122
 123         case PIPE_BLENDFACTOR_INV_CONST_ALPHA:
 124                 return PIPE_BLENDFACTOR_CONST_ALPHA;
 125
 126         default:
 127                 return -1;
 128         }
 129 }
 130
 131 /* Helper to strip the complement from any Gallium blend factor */
 132
 133 static int
 134 uncomplement_factor(int factor)
 135 {
 136         int complement = complement_factor(factor);
 137         return (complement == -1) ? factor : complement;
 138 }
 139
 140
 141 /* Attempt to find the dominant factor given a particular factor, complementing
 142  * as necessary */
 143
 144 static bool
 145 panfrost_make_dominant_factor(unsigned src_factor, enum mali_dominant_factor *factor)
 146 {
 147         switch (src_factor) {
 148         case PIPE_BLENDFACTOR_SRC_COLOR:
 149         case PIPE_BLENDFACTOR_INV_SRC_COLOR:
 150                 *factor = MALI_DOMINANT_SRC_COLOR;
 151                 break;
 152
 153         case PIPE_BLENDFACTOR_SRC_ALPHA:
 154         case PIPE_BLENDFACTOR_INV_SRC_ALPHA:
 155                 *factor = MALI_DOMINANT_SRC_ALPHA;
 156                 break;
 157
 158         case PIPE_BLENDFACTOR_DST_COLOR:
 159         case PIPE_BLENDFACTOR_INV_DST_COLOR:
 160                 *factor = MALI_DOMINANT_DST_COLOR;
 161                 break;
 162
 163         case PIPE_BLENDFACTOR_DST_ALPHA:
 164         case PIPE_BLENDFACTOR_INV_DST_ALPHA:
 165                 *factor = MALI_DOMINANT_DST_ALPHA;
 166                 break;
 167
 168         case PIPE_BLENDFACTOR_ONE:
 169         case PIPE_BLENDFACTOR_ZERO:
 170                 *factor = MALI_DOMINANT_ZERO;
 171                 break;
 172
 173         case PIPE_BLENDFACTOR_CONST_ALPHA:
 174         case PIPE_BLENDFACTOR_INV_CONST_ALPHA:
 175         case PIPE_BLENDFACTOR_CONST_COLOR:
 176         case PIPE_BLENDFACTOR_INV_CONST_COLOR:
 177                 *factor = MALI_DOMINANT_CONSTANT;
 178                 break;
 179
 180         default:
 181                 /* Fancy blend modes not supported */
 182                 return false;
 183         }
 184
 185         return true;
 186 }
 187
 188 /* Check if this is a special edge case blend factor, which may require the use
 189  * of clip modifiers */
 190
 191 static bool
 192 is_edge_blendfactor(unsigned factor)
 193 {
 194         return factor == PIPE_BLENDFACTOR_ONE || factor == PIPE_BLENDFACTOR_ZERO;
 195 }
 196
 197 /* Perform the actual fixed function encoding. Encode the function with negate
 198  * bits. Check for various cases to work out the dominant/nondominant split and
 199  * accompanying flags. */
 200
 201 static bool
 202 panfrost_make_fixed_blend_part(unsigned func, unsigned src_factor, unsigned dst_factor, unsigned *out)
 203 {
 204         struct mali_blend_mode part = { 0 };
 205
 206         /* Make sure that the blend function is representible */
 207
 208         switch (func) {
 209                 case PIPE_BLEND_ADD:
 210                         break;
 211
 212                 /* TODO: Reenable subtraction modes when those fixed */
 213                 case PIPE_BLEND_SUBTRACT:
 214                 case PIPE_BLEND_REVERSE_SUBTRACT:
 215                 default:
 216                         return false;
 217         }
 218
 219         part.clip_modifier = MALI_BLEND_MOD_NORMAL;
 220
 221         /* Decide which is dominant, source or destination. If one is an edge
 222          * case, use the other as a factor. If they're the same, it doesn't
 223          * matter; we just mirror. If they're different non-edge-cases, you
 224          * need a blend shader (don't do that). */
 225
 226         if (is_edge_blendfactor(dst_factor)) {
 227                 part.dominant = MALI_BLEND_DOM_SOURCE;
 228                 part.nondominant_mode = MALI_BLEND_NON_ZERO;
 229
 230                 if (dst_factor == PIPE_BLENDFACTOR_ONE)
 231                         part.clip_modifier = MALI_BLEND_MOD_DEST_ONE;
 232         } else if (is_edge_blendfactor(src_factor)) {
 233                 part.dominant = MALI_BLEND_DOM_DESTINATION;
 234                 part.nondominant_mode = MALI_BLEND_NON_ZERO;
 235
 236                 if (src_factor == PIPE_BLENDFACTOR_ONE)
 237                         part.clip_modifier = MALI_BLEND_MOD_SOURCE_ONE;
 238         } else if (src_factor == dst_factor) {
 239                 /* XXX: Why? */
 240                 part.dominant = func == PIPE_BLEND_ADD ?
 241                         MALI_BLEND_DOM_DESTINATION : MALI_BLEND_DOM_SOURCE;
 242
 243                 part.nondominant_mode = MALI_BLEND_NON_MIRROR;
 244         } else if (src_factor == complement_factor(dst_factor)) {
 245                 /* TODO: How does this work exactly? */
 246                 part.dominant = MALI_BLEND_DOM_SOURCE;
 247                 part.nondominant_mode = MALI_BLEND_NON_MIRROR;
 248                 part.clip_modifier = MALI_BLEND_MOD_DEST_ONE;
 249
 250                 /* The complement is handled by the clip modifier, don't set a
 251                  * complement flag */
 252
 253                 dst_factor = src_factor;
 254         } else if (dst_factor == complement_factor(src_factor)) {
 255                 part.dominant = MALI_BLEND_DOM_SOURCE;
 256                 part.nondominant_mode = MALI_BLEND_NON_MIRROR;
 257                 part.clip_modifier = MALI_BLEND_MOD_SOURCE_ONE;
 258
 259                 src_factor = dst_factor;
 260         } else {
 261                 return false;
 262         }
 263
 264         unsigned in_dominant_factor =
 265                 part.dominant == MALI_BLEND_DOM_SOURCE ? src_factor : dst_factor;
 266
 267         if (part.clip_modifier == MALI_BLEND_MOD_NORMAL && in_dominant_factor == PIPE_BLENDFACTOR_ONE) {
 268                 part.clip_modifier = part.dominant == MALI_BLEND_DOM_SOURCE ? MALI_BLEND_MOD_SOURCE_ONE : MALI_BLEND_MOD_DEST_ONE;
 269                 in_dominant_factor = PIPE_BLENDFACTOR_ZERO;
 270         }
 271
 272         enum mali_dominant_factor dominant_factor;
 273
 274         if (!panfrost_make_dominant_factor(in_dominant_factor, &dominant_factor))
 275                 return false;
 276
 277         part.dominant_factor = dominant_factor;
 278         part.complement_dominant = util_blend_factor_is_inverted(in_dominant_factor);
 279
 280         /* It's not clear what this does, but fixes some ADD blending tests.
 281          * More research is needed XXX */
 282
 283         if ((part.clip_modifier == MALI_BLEND_MOD_SOURCE_ONE) && (part.dominant == MALI_BLEND_DOM_SOURCE))
 284                 part.negate_dest = true;
 285
 286         /* Write out mode */
 287         memcpy(out, &part, sizeof(part));
 288
 289         return true;
 290 }
 291
 292 /* We can upload a single constant for all of the factors. So, scan the factors
 293  * for constants used, and scan the constants for the constants used. If there
 294  * is a single unique constant, output that. If there are multiple,
 295  * fixed-function operation breaks down. */
 296
 297 static bool
 298 panfrost_make_constant(unsigned *factors, unsigned num_factors, const struct pipe_blend_color *blend_color, void *out)
 299 {
 300         /* Color components used */
 301         bool cc[4] = { false };
 302
 303         for (unsigned i = 0; i < num_factors; ++i) {
 304                 unsigned factor = uncomplement_factor(factors[i]);
 305
 306                 if (factor == PIPE_BLENDFACTOR_CONST_COLOR)
 307                         cc[0] = cc[1] = cc[2] = true;
 308                 else if (factor == PIPE_BLENDFACTOR_CONST_ALPHA)
 309                         cc[3] = true;
 310         }
 311
 312         /* Find the actual constant associated with the components used*/
 313
 314         float constant = 0.0;
 315         bool has_constant = false;
 316
 317         for (unsigned i = 0; i < 4; ++i) {
 318                 /* If the component is unused, nothing to do */
 319                 if (!cc[i]) continue;
 320
 321                 float value = blend_color->color[i];
 322
 323                 /* Either there's a second constant, in which case we fail, or
 324                  * there's no constant / a first constant, in which case we use
 325                  * that constant */
 326
 327                 if (has_constant && constant != value) {
 328                         return false;
 329                 } else {
 330                         has_constant = true;
 331                         constant = value;
 332                 }
 333         }
 334
 335         /* We have the constant -- success! */
 336
 337         memcpy(out, &constant, sizeof(float));
 338         return true;
 339 }
 340
 341 /* Create the descriptor for a fixed blend mode given the corresponding Gallium
 342  * state, if possible. Return true and write out the blend descriptor into
 343  * blend_equation. If it is not possible with the fixed function
 344  * representating, return false to handle degenerate cases with a blend shader
 345  */
 346
 347 bool
 348 panfrost_make_fixed_blend_mode(const struct pipe_rt_blend_state *blend, struct panfrost_blend_state *so, unsigned colormask, const struct pipe_blend_color *blend_color)
 349 {
 350         struct mali_blend_equation *out = &so->equation;
 351
 352         /* Gallium and Mali represent colour masks identically. XXX: Static assert for future proof */
 353         out->color_mask = colormask;
 354
 355         /* If no blending is enabled, default back on `replace` mode */
 356
 357         if (!blend->blend_enable) {
 358                 out->rgb_mode = 0x122;
 359                 out->alpha_mode = 0x122;
 360                 return true;
 361         }
 362
 363         /* We have room only for a single float32 constant between the four
 364          * components. If we need more, spill to the programmable pipeline. */
 365
 366         unsigned factors[] = {
 367                 blend->rgb_src_factor, blend->rgb_dst_factor,
 368                 blend->alpha_src_factor, blend->alpha_dst_factor,
 369         };
 370
 371         if (!panfrost_make_constant(factors, ARRAY_SIZE(factors), blend_color, &so->constant))
 372                 return false;
 373
 374         unsigned rgb_mode = 0;
 375         unsigned alpha_mode = 0;
 376
 377         if (!panfrost_make_fixed_blend_part(
 378                                 blend->rgb_func, blend->rgb_src_factor, blend->rgb_dst_factor,
 379                                 &rgb_mode))
 380                 return false;
 381
 382         if (!panfrost_make_fixed_blend_part(
 383                                 blend->alpha_func, blend->alpha_src_factor, blend->alpha_dst_factor,
 384                                 &alpha_mode))
 385                 return false;
 386
 387         out->rgb_mode = rgb_mode;
 388         out->alpha_mode = alpha_mode;
 389
 390         return true;
 391 }