drm/i915: Split obj->cache_coherent to track r/w

Another month, another story in the cache coherency saga. This time, we
come to the realisation that i915_gem_object_is_coherent() has been
reporting whether we can read from the target without requiring a cache
invalidate; but we were using it in places for testing whether we could
write into the object without requiring a cache flush. So split the
tracking into two, one to decide before reads, one after writes.

See commit e27ab73d17ef ("drm/i915: Mark CPU cache as dirty on every
transition for CPU writes") for the previous entry in this saga.

v2: Be verbose
v3: Remove unused function (i915_gem_object_is_coherent)
v4: Fix inverted coherency check prior to execbuf (from v2)
v5: Add comment for nasty code where we are optimising on gcc's behalf.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=101109
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=101555
Testcase: igt/kms_mmap_write_crc
Testcase: igt/kms_pwrite_crc
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Dongwon Kim <dongwon.kim@intel.com>
Cc: Matt Roper <matthew.d.roper@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Tested-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Acked-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20170811111116.10373-1-chris@chris-wilson.co.uk
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>

1 files changed, 13 insertions, 12 deletions

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 000a764ee8d9..887fff281f4e 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -52,7 +52,7 @@ static bool cpu_write_needs_clflush(struct drm_i915_gem_object *obj)
 	if (obj->cache_dirty)
 		return false;
 
-	if (!obj->cache_coherent)
+	if (!(obj->cache_coherent & I915_BO_CACHE_COHERENT_FOR_WRITE))
 		return true;
 
 	return obj->pin_display;
@@ -253,7 +253,7 @@ __i915_gem_object_release_shmem(struct drm_i915_gem_object *obj,
 
 	if (needs_clflush &&
 	    (obj->base.read_domains & I915_GEM_DOMAIN_CPU) == 0 &&
-	    !obj->cache_coherent)
+	    !(obj->cache_coherent & I915_BO_CACHE_COHERENT_FOR_READ))
 		drm_clflush_sg(pages);
 
 	__start_cpu_write(obj);
@@ -800,7 +800,8 @@ int i915_gem_obj_prepare_shmem_read(struct drm_i915_gem_object *obj,
 	if (ret)
 		return ret;
 
-	if (obj->cache_coherent || !static_cpu_has(X86_FEATURE_CLFLUSH)) {
+	if (obj->cache_coherent & I915_BO_CACHE_COHERENT_FOR_READ ||
+	    !static_cpu_has(X86_FEATURE_CLFLUSH)) {
 		ret = i915_gem_object_set_to_cpu_domain(obj, false);
 		if (ret)
 			goto err_unpin;
@@ -852,7 +853,8 @@ int i915_gem_obj_prepare_shmem_write(struct drm_i915_gem_object *obj,
 	if (ret)
 		return ret;
 
-	if (obj->cache_coherent || !static_cpu_has(X86_FEATURE_CLFLUSH)) {
+	if (obj->cache_coherent & I915_BO_CACHE_COHERENT_FOR_WRITE ||
+	    !static_cpu_has(X86_FEATURE_CLFLUSH)) {
 		ret = i915_gem_object_set_to_cpu_domain(obj, true);
 		if (ret)
 			goto err_unpin;
@@ -3673,8 +3675,7 @@ restart:
 
 	list_for_each_entry(vma, &obj->vma_list, obj_link)
 		vma->node.color = cache_level;
-	obj->cache_level = cache_level;
-	obj->cache_coherent = i915_gem_object_is_coherent(obj);
+	i915_gem_object_set_cache_coherency(obj, cache_level);
 	obj->cache_dirty = true; /* Always invalidate stale cachelines */
 
 	return 0;
@@ -4279,6 +4280,7 @@ i915_gem_object_create(struct drm_i915_private *dev_priv, u64 size)
 {
 	struct drm_i915_gem_object *obj;
 	struct address_space *mapping;
+	unsigned int cache_level;
 	gfp_t mask;
 	int ret;
 
@@ -4317,7 +4319,7 @@ i915_gem_object_create(struct drm_i915_private *dev_priv, u64 size)
 	obj->base.write_domain = I915_GEM_DOMAIN_CPU;
 	obj->base.read_domains = I915_GEM_DOMAIN_CPU;
 
-	if (HAS_LLC(dev_priv)) {
+	if (HAS_LLC(dev_priv))
 		/* On some devices, we can have the GPU use the LLC (the CPU
 		 * cache) for about a 10% performance improvement
 		 * compared to uncached.  Graphics requests other than
@@ -4330,12 +4332,11 @@ i915_gem_object_create(struct drm_i915_private *dev_priv, u64 size)
 		 * However, we maintain the display planes as UC, and so
 		 * need to rebind when first used as such.
 		 */
-		obj->cache_level = I915_CACHE_LLC;
-	} else
-		obj->cache_level = I915_CACHE_NONE;
+		cache_level = I915_CACHE_LLC;
+	else
+		cache_level = I915_CACHE_NONE;
 
-	obj->cache_coherent = i915_gem_object_is_coherent(obj);
-	obj->cache_dirty = !obj->cache_coherent;
+	i915_gem_object_set_cache_coherency(obj, cache_level);
 
 	trace_i915_gem_object_create(obj);