[Intel-gfx] [PATCH] drm/i915: Add a comment about WIZ hashing vs. thread counts

[ville.syrjala at linux.intel.com]

From: Ville Syrjälä <ville.syrjala at linux.intel.com>

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 at chris-wilson.co.uk>
Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
---
 drivers/gpu/drm/i915/intel_pm.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index c3a1362..a3b61ca 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -4647,6 +4647,10 @@ 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);
@@ -4830,6 +4834,10 @@ 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);
@@ -4866,6 +4874,10 @@ 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);
@@ -4954,6 +4966,10 @@ 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);
-- 
1.8.3.2