[PATCH 41/56] drm/i915/bdw: Optimize PDP loads

[Ben Widawsky <benjamin.widawsky@intel.com>]

Don't do them if they're not necessary, which they're not, for the RCS,
in certain conditions.

Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
---
 drivers/gpu/drm/i915/i915_gem_gtt.c | 20 ++++++++++++++++++++
 drivers/gpu/drm/i915/i915_gem_gtt.h |  1 +
 2 files changed, 21 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
index d8bb4dc..3ea0c7d 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.c
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
@@ -438,8 +438,20 @@ static int gen8_mm_switch(struct i915_hw_ppgtt *ppgtt,
 			  struct intel_ring_buffer *ring,
 			  bool synchronous)
 {
+	struct drm_i915_private *dev_priv = ring->dev->dev_private;
 	int i, ret;
 
+	/* The RCS ring gets reloaded by the hardware context state. So we only
+	 * need to actually reload if one of the page directory pointer have
+	 * changed, or it's !RCS
+	 *
+	 * Aliasing PPGTT remains special, as we do not track it's
+	 * reloading needs.
+	 */
+	if (ppgtt != dev_priv->mm.aliasing_ppgtt &&
+	    ring->id == RCS && !ppgtt->pdp.needs_reload)
+		return 0;
+
 	for (i = GEN8_LEGACY_PDPES - 1; i >= 0; i--) {
 		struct i915_pagedir *pd = ppgtt->pdp.pagedirs[i];
 		dma_addr_t addr = pd ? pd->daddr : ppgtt->scratch_pt->daddr;
@@ -450,6 +462,9 @@ static int gen8_mm_switch(struct i915_hw_ppgtt *ppgtt,
 			return ret;
 	}
 
+
+	ppgtt->pdp.needs_reload = 0;
+
 	return 0;
 }
 
@@ -651,6 +666,7 @@ static void gen8_teardown_va_range(struct i915_address_space *vm,
 			free_pd_single(pd, vm->dev);
 			ppgtt->pdp.pagedirs[pdpe] = NULL;
 			WARN_ON(!test_and_clear_bit(pdpe, ppgtt->pdp.used_pdpes));
+			ppgtt->pdp.needs_reload = 1;
 		}
 	}
 }
@@ -901,6 +917,8 @@ static int gen8_alloc_va_range(struct i915_address_space *vm,
 		}
 
 		set_bit(pdpe, ppgtt->pdp.used_pdpes);
+		if (test_and_set_bit(pdpe, ppgtt->pdp.used_pdpes))
+			ppgtt->pdp.needs_reload = 1;
 
 		gen8_map_pagetable_range(pd, start, length, ppgtt->base.dev);
 	}
@@ -937,6 +955,8 @@ static int gen8_ppgtt_init_common(struct i915_hw_ppgtt *ppgtt, uint64_t size)
 	ppgtt->switch_mm = gen8_mm_switch;
 	ppgtt->base.insert_entries = gen8_ppgtt_insert_entries;
 
+	ppgtt->pdp.needs_reload = 1;
+
 	ppgtt->scratch_pd = alloc_pt_scratch(ppgtt->base.dev);
 	if (IS_ERR(ppgtt->scratch_pd))
 		return PTR_ERR(ppgtt->scratch_pd);
diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.h b/drivers/gpu/drm/i915/i915_gem_gtt.h
index b3d0776..dd561f3 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.h
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.h
@@ -198,6 +198,7 @@ struct i915_pagedirpo {
 	/* struct page *page; */
 	DECLARE_BITMAP(used_pdpes, GEN8_LEGACY_PDPES);
 	struct i915_pagedir *pagedirs[GEN8_LEGACY_PDPES];
+	unsigned needs_reload:1;
 };
 
 struct i915_address_space {
-- 
1.9.2