drm/i915: Add a comment about WIZ hashing vs. thread counts

Add a comment next to our WIZ hashing setup to remind people about the
link between WIZ hashing disable bit and PS/WM thread counts.

Suggested-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 16 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 151afe53cc7c..3e754fec58b5 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -4664,6 +4664,10 @@ static void gen6_init_clock_gating(struct drm_device *dev)
         /*
          * BSpec recoomends 8x4 when MSAA is used,
          * however in practice 16x4 seems fastest.
+         *
+         * Note that PS/WM thread counts depend on the WIZ hashing
+         * disable bit, which we don't touch here, but it's good
+         * to keep in mind (see 3DSTATE_PS and 3DSTATE_WM).
          */
         I915_WRITE(GEN6_GT_MODE,
                    GEN6_WIZ_HASHING_MASK | GEN6_WIZ_HASHING_16x4);
@@ -4847,6 +4851,10 @@ static void gen8_init_clock_gating(struct drm_device *dev)
         /*
          * BSpec recommends 8x4 when MSAA is used,
          * however in practice 16x4 seems fastest.
+         *
+         * Note that PS/WM thread counts depend on the WIZ hashing
+         * disable bit, which we don't touch here, but it's good
+         * to keep in mind (see 3DSTATE_PS and 3DSTATE_WM).
          */
         I915_WRITE(GEN7_GT_MODE,
                    GEN6_WIZ_HASHING_MASK | GEN6_WIZ_HASHING_16x4);
@@ -4883,6 +4891,10 @@ static void haswell_init_clock_gating(struct drm_device *dev)
         /*
          * BSpec recommends 8x4 when MSAA is used,
          * however in practice 16x4 seems fastest.
+         *
+         * Note that PS/WM thread counts depend on the WIZ hashing
+         * disable bit, which we don't touch here, but it's good
+         * to keep in mind (see 3DSTATE_PS and 3DSTATE_WM).
          */
         I915_WRITE(GEN7_GT_MODE,
                    GEN6_WIZ_HASHING_MASK | GEN6_WIZ_HASHING_16x4);
@@ -4971,6 +4983,10 @@ static void ivybridge_init_clock_gating(struct drm_device *dev)
         /*
          * BSpec recommends 8x4 when MSAA is used,
          * however in practice 16x4 seems fastest.
+         *
+         * Note that PS/WM thread counts depend on the WIZ hashing
+         * disable bit, which we don't touch here, but it's good
+         * to keep in mind (see 3DSTATE_PS and 3DSTATE_WM).
          */
         I915_WRITE(GEN7_GT_MODE,
                    GEN6_WIZ_HASHING_MASK | GEN6_WIZ_HASHING_16x4);