panfrost: Implement sRGB blend shaders

We use the lowering in nir_format_convert. There are native ops for this
so this is far from optimal and not remotely efficient but as with most
blend shader things right now, it's hard enough to get it working, so
let's focus on that for now. We'll make it fast later (once we have
GLES3 stable, we can start optimizing these things).

Fixes dEQP-GLES3.functional.fragment_ops.blend.fbo_srgb.*

Signed-off-by: Alyssa Rosenzweig <[email protected]>
Reviewed-by: Tomeu Vizoso <[email protected]>

2 files changed, 16 insertions, 8 deletions

diff --git a/src/gallium/drivers/panfrost/nir/nir_lower_framebuffer.c b/src/gallium/drivers/panfrost/nir/nir_lower_framebuffer.c
index ffb51c4c3a1..887b3662dc3 100644
--- a/src/gallium/drivers/panfrost/nir/nir_lower_framebuffer.c
+++ b/src/gallium/drivers/panfrost/nir/nir_lower_framebuffer.c
@@ -338,6 +338,22 @@ nir_lower_framebuffer(nir_shader *shader, enum pipe_format format,
                /* Grab the input color */
                nir_ssa_def *c_nir = nir_ssa_for_src(&b, intr->src[1], 4);
 
+               /* Apply sRGB transform */
+
+               if (format_desc->colorspace == UTIL_FORMAT_COLORSPACE_SRGB) {
+                  nir_ssa_def *rgb = nir_channels(&b, c_nir, 0x7);
+                  nir_ssa_def *trans = nir_format_linear_to_srgb(&b, rgb);
+
+                  nir_ssa_def *comp[4] = {
+                     nir_channel(&b, trans, 0),
+                     nir_channel(&b, trans, 1),
+                     nir_channel(&b, trans, 2),
+                     nir_channel(&b, c_nir, 3),
+                  };
+
+                  c_nir = nir_vec(&b, comp, 4);
+               }
+
                /* Format convert */
                nir_ssa_def *converted = nir_shader_to_native(&b, c_nir, format_desc, bits, homogenous_bits);
 
diff --git a/src/gallium/drivers/panfrost/pan_context.c b/src/gallium/drivers/panfrost/pan_context.c
index 8c911b5d001..9c51f423f86 100644
--- a/src/gallium/drivers/panfrost/pan_context.c
+++ b/src/gallium/drivers/panfrost/pan_context.c
@@ -1037,14 +1037,6 @@ panfrost_emit_for_draw(struct panfrost_context *ctx, bool with_vertex_data)
                                 SET_BIT(rts[i].flags, MALI_BLEND_SRGB, is_srgb);
                                 SET_BIT(rts[i].flags, MALI_BLEND_NO_DITHER, !ctx->blend->base.dither);
 
-                                /* TODO: sRGB in blend shaders is currently
-                                 * unimplemented. Contact me (Alyssa) if you're
-                                 * interested in working on this. We have
-                                 * native Midgard ops for helping here, but
-                                 * they're not well-understood yet. */
-
-                                assert(!(is_srgb && blend[i].is_shader));
-
                                 if (blend[i].is_shader) {
                                         rts[i].blend.shader = blend[i].shader.gpu | blend[i].shader.first_tag;
                                 } else {