panfrost: Add support for decoding gl_FrontFacing

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

2 files changed, 11 insertions, 1 deletions

diff --git a/src/panfrost/include/panfrost-job.h b/src/panfrost/include/panfrost-job.h
index ffe1bf25aa4..9179ceff2ec 100644
--- a/src/panfrost/include/panfrost-job.h
+++ b/src/panfrost/include/panfrost-job.h
@@ -788,6 +788,10 @@ struct mali_payload_set_value {
  * implemented as special attributes, denoted by MALI_ATTR_IMAGE. For images,
  * let shift=extra_flags=0. Stride is set to the image format's bytes-per-pixel
  * (*NOT the row stride*). Size is set to the size of the image itself.
+ *
+ * Special internal varyings (including gl_FrontFacing) are handled vai
+ * MALI_ATTR_INTERNAL, which has all fields set to zero and uses a special
+ * elements pseudo-pointer.
  */
 
 enum mali_attr_mode {
@@ -796,9 +800,14 @@ enum mali_attr_mode {
 	MALI_ATTR_POT_DIVIDE = 2,
 	MALI_ATTR_MODULO = 3,
 	MALI_ATTR_NPOT_DIVIDE = 4,
-        MALI_ATTR_IMAGE = 5
+        MALI_ATTR_IMAGE = 5,
+        MALI_ATTR_INTERNAL = 6
 };
 
+/* Pseudo-address for gl_FrontFacing */
+
+#define MALI_VARYING_FRONT_FACING (0x20)
+
 /* This magic "pseudo-address" is used as `elements` to implement
  * gl_PointCoord. When read from a fragment shader, it generates a point
  * coordinate per the OpenGL ES 2.0 specification. Flipped coordinate spaces
diff --git a/src/panfrost/pandecode/decode.c b/src/panfrost/pandecode/decode.c
index a44c3732477..080d650fc5a 100644
--- a/src/panfrost/pandecode/decode.c
+++ b/src/panfrost/pandecode/decode.c
@@ -382,6 +382,7 @@ static char *pandecode_attr_mode(enum mali_attr_mode mode)
                 DEFINE_CASE(MODULO);
                 DEFINE_CASE(NPOT_DIVIDE);
                 DEFINE_CASE(IMAGE);
+                DEFINE_CASE(INTERNAL);
         default:
                 return "MALI_ATTR_UNUSED /* XXX: Unknown stencil op, check dump */";
         }