[Intel-gfx] [PATCH] drm/i915: Enable eLLC caching of display buffers for SKL+

[Ville Syrjala]

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

Since SKL the eLLC has been sitting on the far side of the system
agent, meaning the display engine can utilize it. Let's enable that.

I chose WB for the caching mode, because my numbers are indicating
that WT might actually be WB and WC might actually be UC. I'm not
100% sure that is indeed the case but at least my simple rendercopy
based benchmark didn't see any difference in performance.

Also if I configure things to do LLCeLLC+WT I still get cache dirt
on my screen, suggesting that is in fact operating in WB mode
anyway. This is also the reason I had to fix the MOCS target cache
to really say PTE rather than LLC+eLLC.

Caveat: I've not benchmarked any real workloads. IIRC Eero did
benchmark an earlier version, but that didn't have the PTE vs.
LLC+eLLC MOCS fix so it wasn't actually doing the right thing
most likely.

Cc: Eero Tamminen <eero.t.tamminen at intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
---
 drivers/gpu/drm/i915/i915_drv.h     | 3 +--
 drivers/gpu/drm/i915/i915_gem_gtt.c | 7 +++++--
 drivers/gpu/drm/i915/i915_gem_gtt.h | 2 +-
 drivers/gpu/drm/i915/intel_mocs.c   | 2 +-
 4 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 35d0782c077e..2a4f33fa2bba 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2517,8 +2517,7 @@ IS_SUBPLATFORM(const struct drm_i915_private *i915,
 #define HAS_LLC(dev_priv)	(INTEL_INFO(dev_priv)->has_llc)
 #define HAS_SNOOP(dev_priv)	(INTEL_INFO(dev_priv)->has_snoop)
 #define HAS_EDRAM(dev_priv)	((dev_priv)->edram_size_mb)
-#define HAS_WT(dev_priv)	((IS_HASWELL(dev_priv) || \
-				 IS_BROADWELL(dev_priv)) && HAS_EDRAM(dev_priv))
+#define HAS_WT(dev_priv)	HAS_EDRAM(dev_priv)
 
 #define HWS_NEEDS_PHYSICAL(dev_priv)	(INTEL_INFO(dev_priv)->hws_needs_physical)
 
diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
index 8f460cc4cc1f..038fbf52a997 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.c
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
@@ -3071,7 +3071,7 @@ static void cnl_setup_private_ppat(struct intel_ppat *ppat)
 
 	__alloc_ppat_entry(ppat, 0, GEN8_PPAT_WB | GEN8_PPAT_LLC);
 	__alloc_ppat_entry(ppat, 1, GEN8_PPAT_WC | GEN8_PPAT_LLCELLC);
-	__alloc_ppat_entry(ppat, 2, GEN8_PPAT_WT | GEN8_PPAT_LLCELLC);
+	__alloc_ppat_entry(ppat, 2, GEN8_PPAT_WB | GEN8_PPAT_ELLC_OVERRIDE);
 	__alloc_ppat_entry(ppat, 3, GEN8_PPAT_UC);
 	__alloc_ppat_entry(ppat, 4, GEN8_PPAT_WB | GEN8_PPAT_LLCELLC | GEN8_PPAT_AGE(0));
 	__alloc_ppat_entry(ppat, 5, GEN8_PPAT_WB | GEN8_PPAT_LLCELLC | GEN8_PPAT_AGE(1));
@@ -3109,7 +3109,10 @@ static void bdw_setup_private_ppat(struct intel_ppat *ppat)
 
 	__alloc_ppat_entry(ppat, 0, GEN8_PPAT_WB | GEN8_PPAT_LLC);      /* for normal objects, no eLLC */
 	__alloc_ppat_entry(ppat, 1, GEN8_PPAT_WC | GEN8_PPAT_LLCELLC);  /* for something pointing to ptes? */
-	__alloc_ppat_entry(ppat, 2, GEN8_PPAT_WT | GEN8_PPAT_LLCELLC);  /* for scanout with eLLC */
+	if (INTEL_GEN(ppat->i915) >= 9)
+		__alloc_ppat_entry(ppat, 2, GEN8_PPAT_WB | GEN8_PPAT_ELLC_OVERRIDE); /* for scanout with eLLC */
+	else
+		__alloc_ppat_entry(ppat, 2, GEN8_PPAT_WT | GEN8_PPAT_LLCELLC); /* for scanout with eLLC */
 	__alloc_ppat_entry(ppat, 3, GEN8_PPAT_UC);                      /* Uncached objects, mostly for scanout */
 	__alloc_ppat_entry(ppat, 4, GEN8_PPAT_WB | GEN8_PPAT_LLCELLC | GEN8_PPAT_AGE(0));
 	__alloc_ppat_entry(ppat, 5, GEN8_PPAT_WB | GEN8_PPAT_LLCELLC | GEN8_PPAT_AGE(1));
diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.h b/drivers/gpu/drm/i915/i915_gem_gtt.h
index f597f35b109b..47adc7268867 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.h
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.h
@@ -139,7 +139,7 @@ typedef u64 gen8_ppgtt_pml4e_t;
 #define PPAT_UNCACHED			(_PAGE_PWT | _PAGE_PCD)
 #define PPAT_CACHED_PDE			0 /* WB LLC */
 #define PPAT_CACHED			_PAGE_PAT /* WB LLCeLLC */
-#define PPAT_DISPLAY_ELLC		_PAGE_PCD /* WT eLLC */
+#define PPAT_DISPLAY_ELLC		_PAGE_PCD /* WT LLCeLLC (HSW/BDW) or WB eLLC (SKL+) */
 
 #define CHV_PPAT_SNOOP			(1<<6)
 #define GEN8_PPAT_AGE(x)		((x)<<4)
diff --git a/drivers/gpu/drm/i915/intel_mocs.c b/drivers/gpu/drm/i915/intel_mocs.c
index 274ba78500c0..d984ccff94ef 100644
--- a/drivers/gpu/drm/i915/intel_mocs.c
+++ b/drivers/gpu/drm/i915/intel_mocs.c
@@ -115,7 +115,7 @@ struct drm_i915_mocs_table {
 		   LE_1_UC | LE_TC_2_LLC_ELLC, \
 		   L3_1_UC), \
 	MOCS_ENTRY(I915_MOCS_PTE, \
-		   LE_0_PAGETABLE | LE_TC_2_LLC_ELLC | LE_LRUM(3), \
+		   LE_0_PAGETABLE | LE_TC_0_PAGETABLE | LE_LRUM(3), \
 		   L3_3_WB)
 
 static const struct drm_i915_mocs_entry skylake_mocs_table[] = {
-- 
2.21.0