2 * © Copyright 2018 Alyssa Rosenzweig
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26 #include "pan_blending.h"
27 #include "pan_context.h"
28 #include "gallium/auxiliary/util/u_blend.h"
29 #include "util/format/u_format.h"
32 * Implements fixed-function blending on Midgard.
34 * Midgard splits blending into a fixed-function fast path and a programmable
35 * slow path. The fixed function blending architecture is based on "dominant"
36 * blend factors. Blending is encoded separately (but identically) between RGB
37 * and alpha functions.
39 * Essentially, for a given blending operation, there is a single dominant
40 * factor. The following dominant factors are possible:
49 * Further, a dominant factor's arithmetic compliment could be used. For
50 * instance, to encode GL_ONE_MINUS_SOURCE_ALPHA, the dominant factor would be
51 * MALI_DOMINANT_SRC_ALPHA with the complement_dominant bit set.
53 * A single constant float can be passed to the fixed-function hardware,
54 * allowing CONSTANT_ALPHA support. Further, if all components of the constant
55 * glBlendColor are identical, CONSTANT_COLOR can be implemented with the
56 * constant float mode. If the components differ, programmable blending is
59 * The nondominant factor can be either:
61 * - the same as the dominant factor (MALI_BLEND_NON_MIRROR)
62 * - zero (MALI_BLEND_NON_ZERO)
64 * Exactly one of the blend operation's source or destination can be used as
65 * the dominant factor; this is selected by the
66 * MALI_BLEND_DOM_SOURCE/DESTINATION flag.
68 * By default, all blending follows the standard OpenGL addition equation:
70 * out = source_value * source_factor + destination_value * destination_factor
72 * By setting the negate_source or negate_dest bits, other blend functions can
73 * be created. For instance, for SUBTRACT mode, set the "negate destination"
74 * flag, and similarly for REVERSE_SUBTRACT with "negate source".
76 * Finally, there is a "clip modifier" controlling the final blending
77 * behaviour, allowing for the following modes:
80 * - force source factor to one (MALI_BLEND_MODE_SOURCE_ONE)
81 * - force destination factor to one (MALI_BLEND_MODE_DEST_ONE)
83 * The clipping flags can be used to encode blend modes where the nondominant
86 * As an example putting it all together, to encode the following blend state:
88 * glBlendEquation(GL_FUNC_REVERSE_SUBTRACT);
89 * glBlendFunc(GL_ONE_MINUS_SRC_ALPHA, GL_ONE);
91 * We need the following configuration:
93 * - negate source (for REVERSE_SUBTRACT)
94 * - dominant factor "source alpha"
95 * - complement dominant
97 * - force destination to ONE
99 * The following routines implement this fixed function blending encoding
102 /* Not all formats can be blended by fixed-function hardware */
105 panfrost_can_fixed_blend(enum pipe_format format
)
107 /* Fixed-function can handle sRGB */
108 format
= util_format_linear(format
);
110 switch (panfrost_pipe_format_table
[format
].hw
) {
112 case MALI_RGB5_A1_UNORM
:
113 case MALI_RGB10_A2_UNORM
:
114 case MALI_RGBA4_UNORM
:
117 case MALI_RGB8_UNORM
:
118 case MALI_RGBA8_UNORM
:
125 /* Helper to find the uncomplemented Gallium blend factor corresponding to a
126 * complemented Gallium blend factor */
129 complement_factor(int factor
)
132 case PIPE_BLENDFACTOR_INV_SRC_COLOR
:
133 return PIPE_BLENDFACTOR_SRC_COLOR
;
135 case PIPE_BLENDFACTOR_INV_SRC_ALPHA
:
136 return PIPE_BLENDFACTOR_SRC_ALPHA
;
138 case PIPE_BLENDFACTOR_INV_DST_ALPHA
:
139 return PIPE_BLENDFACTOR_DST_ALPHA
;
141 case PIPE_BLENDFACTOR_INV_DST_COLOR
:
142 return PIPE_BLENDFACTOR_DST_COLOR
;
144 case PIPE_BLENDFACTOR_INV_CONST_COLOR
:
145 return PIPE_BLENDFACTOR_CONST_COLOR
;
147 case PIPE_BLENDFACTOR_INV_CONST_ALPHA
:
148 return PIPE_BLENDFACTOR_CONST_ALPHA
;
155 /* Helper to strip the complement from any Gallium blend factor */
158 uncomplement_factor(int factor
)
160 int complement
= complement_factor(factor
);
161 return (complement
== -1) ? factor
: complement
;
165 /* Attempt to find the dominant factor given a particular factor, complementing
169 panfrost_make_dominant_factor(unsigned src_factor
, enum mali_dominant_factor
*factor
)
171 switch (src_factor
) {
172 case PIPE_BLENDFACTOR_SRC_COLOR
:
173 case PIPE_BLENDFACTOR_INV_SRC_COLOR
:
174 *factor
= MALI_DOMINANT_SRC_COLOR
;
177 case PIPE_BLENDFACTOR_SRC_ALPHA
:
178 case PIPE_BLENDFACTOR_INV_SRC_ALPHA
:
179 *factor
= MALI_DOMINANT_SRC_ALPHA
;
182 case PIPE_BLENDFACTOR_DST_COLOR
:
183 case PIPE_BLENDFACTOR_INV_DST_COLOR
:
184 *factor
= MALI_DOMINANT_DST_COLOR
;
187 case PIPE_BLENDFACTOR_DST_ALPHA
:
188 case PIPE_BLENDFACTOR_INV_DST_ALPHA
:
189 *factor
= MALI_DOMINANT_DST_ALPHA
;
192 case PIPE_BLENDFACTOR_ONE
:
193 case PIPE_BLENDFACTOR_ZERO
:
194 *factor
= MALI_DOMINANT_ZERO
;
197 case PIPE_BLENDFACTOR_CONST_ALPHA
:
198 case PIPE_BLENDFACTOR_INV_CONST_ALPHA
:
199 case PIPE_BLENDFACTOR_CONST_COLOR
:
200 case PIPE_BLENDFACTOR_INV_CONST_COLOR
:
201 *factor
= MALI_DOMINANT_CONSTANT
;
205 /* Fancy blend modes not supported */
212 /* Check if this is a special edge case blend factor, which may require the use
213 * of clip modifiers */
216 is_edge_blendfactor(unsigned factor
)
218 return factor
== PIPE_BLENDFACTOR_ONE
|| factor
== PIPE_BLENDFACTOR_ZERO
;
221 /* Perform the actual fixed function encoding. Encode the function with negate
222 * bits. Check for various cases to work out the dominant/nondominant split and
223 * accompanying flags. */
226 panfrost_make_fixed_blend_part(unsigned func
, unsigned src_factor
, unsigned dst_factor
, unsigned *out
)
228 struct mali_blend_mode part
= { 0 };
230 /* Make sure that the blend function is representible */
236 /* TODO: Reenable subtraction modes when those fixed */
237 case PIPE_BLEND_SUBTRACT
:
238 case PIPE_BLEND_REVERSE_SUBTRACT
:
243 part
.clip_modifier
= MALI_BLEND_MOD_NORMAL
;
245 /* Decide which is dominant, source or destination. If one is an edge
246 * case, use the other as a factor. If they're the same, it doesn't
247 * matter; we just mirror. If they're different non-edge-cases, you
248 * need a blend shader (don't do that). */
250 if (is_edge_blendfactor(dst_factor
)) {
251 part
.dominant
= MALI_BLEND_DOM_SOURCE
;
252 part
.nondominant_mode
= MALI_BLEND_NON_ZERO
;
254 if (dst_factor
== PIPE_BLENDFACTOR_ONE
)
255 part
.clip_modifier
= MALI_BLEND_MOD_DEST_ONE
;
256 } else if (is_edge_blendfactor(src_factor
)) {
257 part
.dominant
= MALI_BLEND_DOM_DESTINATION
;
258 part
.nondominant_mode
= MALI_BLEND_NON_ZERO
;
260 if (src_factor
== PIPE_BLENDFACTOR_ONE
)
261 part
.clip_modifier
= MALI_BLEND_MOD_SOURCE_ONE
;
262 } else if (src_factor
== dst_factor
) {
264 part
.dominant
= func
== PIPE_BLEND_ADD
?
265 MALI_BLEND_DOM_DESTINATION
: MALI_BLEND_DOM_SOURCE
;
267 part
.nondominant_mode
= MALI_BLEND_NON_MIRROR
;
268 } else if (src_factor
== complement_factor(dst_factor
)) {
269 /* TODO: How does this work exactly? */
270 part
.dominant
= MALI_BLEND_DOM_SOURCE
;
271 part
.nondominant_mode
= MALI_BLEND_NON_MIRROR
;
272 part
.clip_modifier
= MALI_BLEND_MOD_DEST_ONE
;
274 /* The complement is handled by the clip modifier, don't set a
277 dst_factor
= src_factor
;
278 } else if (dst_factor
== complement_factor(src_factor
)) {
279 part
.dominant
= MALI_BLEND_DOM_SOURCE
;
280 part
.nondominant_mode
= MALI_BLEND_NON_MIRROR
;
281 part
.clip_modifier
= MALI_BLEND_MOD_SOURCE_ONE
;
283 src_factor
= dst_factor
;
288 unsigned in_dominant_factor
=
289 part
.dominant
== MALI_BLEND_DOM_SOURCE
? src_factor
: dst_factor
;
291 if (part
.clip_modifier
== MALI_BLEND_MOD_NORMAL
&& in_dominant_factor
== PIPE_BLENDFACTOR_ONE
) {
292 part
.clip_modifier
= part
.dominant
== MALI_BLEND_DOM_SOURCE
? MALI_BLEND_MOD_SOURCE_ONE
: MALI_BLEND_MOD_DEST_ONE
;
293 in_dominant_factor
= PIPE_BLENDFACTOR_ZERO
;
296 enum mali_dominant_factor dominant_factor
;
298 if (!panfrost_make_dominant_factor(in_dominant_factor
, &dominant_factor
))
301 part
.dominant_factor
= dominant_factor
;
302 part
.complement_dominant
= util_blend_factor_is_inverted(in_dominant_factor
);
304 /* It's not clear what this does, but fixes some ADD blending tests.
305 * More research is needed XXX */
307 if ((part
.clip_modifier
== MALI_BLEND_MOD_SOURCE_ONE
) && (part
.dominant
== MALI_BLEND_DOM_SOURCE
))
308 part
.negate_dest
= true;
311 memcpy(out
, &part
, sizeof(part
));
316 /* We can upload a single constant for all of the factors. So, scan
317 * the factors for constants used to create a mask to check later. */
320 panfrost_constant_mask(unsigned *factors
, unsigned num_factors
)
324 for (unsigned i
= 0; i
< num_factors
; ++i
) {
325 unsigned factor
= uncomplement_factor(factors
[i
]);
327 if (factor
== PIPE_BLENDFACTOR_CONST_COLOR
)
328 mask
|= 0b0111; /* RGB */
329 else if (factor
== PIPE_BLENDFACTOR_CONST_ALPHA
)
330 mask
|= 0b1000; /* A */
336 /* Create the descriptor for a fixed blend mode given the corresponding Gallium
337 * state, if possible. Return true and write out the blend descriptor into
338 * blend_equation. If it is not possible with the fixed function
339 * representating, return false to handle degenerate cases with a blend shader
343 panfrost_make_fixed_blend_mode(
344 const struct pipe_rt_blend_state
*blend
,
345 struct mali_blend_equation
*out
,
346 unsigned *constant_mask
,
349 /* Gallium and Mali represent colour masks identically. XXX: Static
350 * assert for future proof */
352 out
->color_mask
= colormask
;
354 /* If no blending is enabled, default back on `replace` mode */
356 if (!blend
->blend_enable
) {
357 out
->rgb_mode
= 0x122;
358 out
->alpha_mode
= 0x122;
362 /* At draw-time, we'll need to analyze the blend constant, so
363 * precompute a mask for it -- even if we don't end up able to use
364 * fixed-function blending */
366 unsigned factors
[] = {
367 blend
->rgb_src_factor
, blend
->rgb_dst_factor
,
368 blend
->alpha_src_factor
, blend
->alpha_dst_factor
,
371 *constant_mask
= panfrost_constant_mask(factors
, ARRAY_SIZE(factors
));
373 /* Try to compile the actual fixed-function blend */
375 unsigned rgb_mode
= 0;
376 unsigned alpha_mode
= 0;
378 if (!panfrost_make_fixed_blend_part(
379 blend
->rgb_func
, blend
->rgb_src_factor
, blend
->rgb_dst_factor
,
383 if (!panfrost_make_fixed_blend_part(
384 blend
->alpha_func
, blend
->alpha_src_factor
, blend
->alpha_dst_factor
,
388 out
->rgb_mode
= rgb_mode
;
389 out
->alpha_mode
= alpha_mode
;