[Mesa-dev] [PATCH] etnaviv: Fix point sprite issue on HALTI0

[Wladimir J. van der Laan]

A recent commit (see below) fixed flat shading but at the same time
broke the use of point sprites with multiple varyings. This resulted in
particle systems rendering wrongly.

The reason for this is that it set VARYING_COMPONENT_USE_POINTCOORD_[XY]
for all non-color varyings, causing them to be replaced with the point
coordinate when rendering points.

VARYING_COMPONENT_USE_POINTCOORD_[XY] is a misnomer, it should be
TEXCOORD. Its semantics are: texture coordinates will get replaced with
the point coordinate when rendering GL_POINTS, for other primitives
their interpolation is independent of the shading model.

So use VARYING_COMPONENT_USE_POINTCOORD_[XY] only for texture coordinates.
This causes them to be interpolated correctly while flat shading, while
generic varyings are left as-is when rendering point sprites.

Fixes: cedab87e762aa38997a07bc8a2eb624aed584afd "etnaviv: fix varying interpolation"
Signed-off-by: Wladimir J. van der Laan <laanwj at gmail.com>
---
 src/gallium/drivers/etnaviv/etnaviv_compiler.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/src/gallium/drivers/etnaviv/etnaviv_compiler.c b/src/gallium/drivers/etnaviv/etnaviv_compiler.c
index 3180646..6569979 100644
--- a/src/gallium/drivers/etnaviv/etnaviv_compiler.c
+++ b/src/gallium/drivers/etnaviv/etnaviv_compiler.c
@@ -2561,7 +2561,11 @@ etna_link_shader(struct etna_shader_link_info *info,
       const struct etna_shader_inout *fsio = &fs->infile.reg[idx];
       const struct etna_shader_inout *vsio = etna_shader_vs_lookup(vs, fsio);
       struct etna_varying *varying;
-      bool interpolate_always = fsio->semantic.Name != TGSI_SEMANTIC_COLOR;
+      /* Texture coordinates will get replaced with the point coordinate when
+       * rendering GL_POINTS, for other primitives their interpolation is
+       * independent of the shading model. */
+      bool is_texcoord = fsio->semantic.Name == TGSI_SEMANTIC_TEXCOORD ||
+                         fsio->semantic.Name == TGSI_SEMANTIC_PCOORD;
 
       assert(fsio->reg > 0 && fsio->reg <= ARRAY_SIZE(info->varyings));
 
@@ -2571,13 +2575,14 @@ etna_link_shader(struct etna_shader_link_info *info,
       varying = &info->varyings[fsio->reg - 1];
       varying->num_components = fsio->num_components;
 
-      if (!interpolate_always) /* colors affected by flat shading */
+      /* PA_ATTRIBUTES appears to be unused on HALTI0 and up */
+      if (!is_texcoord) /* colors affected by flat shading */
          varying->pa_attributes = 0x200;
       else /* texture coord or other bypasses flat shading */
          varying->pa_attributes = 0x2f1;
 
-      varying->use[0] = interpolate_always ? VARYING_COMPONENT_USE_POINTCOORD_X : VARYING_COMPONENT_USE_USED;
-      varying->use[1] = interpolate_always ? VARYING_COMPONENT_USE_POINTCOORD_Y : VARYING_COMPONENT_USE_USED;
+      varying->use[0] = is_texcoord ? VARYING_COMPONENT_USE_POINTCOORD_X : VARYING_COMPONENT_USE_USED;
+      varying->use[1] = is_texcoord ? VARYING_COMPONENT_USE_POINTCOORD_Y : VARYING_COMPONENT_USE_USED;
       varying->use[2] = VARYING_COMPONENT_USE_USED;
       varying->use[3] = VARYING_COMPONENT_USE_USED;
 
-- 
2.7.4