[PATCH 1/2] drm/i915: Simplify flush_cpu_write_domain

Daniel Vetter
2015-01-21T13:53:59Z

We can push down the decision whether to force flushing into the
implementation since in all places that matter obj->pin_display is
accurate already. The only place where the optimization really matters
is the sw_finish_ioctl, and that already checks for obj->pin_display
on its own.

I suspect that this was simply an artifact of how

commit 2c22569bba8af6c2976d5f9479fe54a53a39966b
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date: Fri Aug 9 12:26:45 2013 +0100

drm/i915: Update rules for writing through the LLC with the cpu

evolved - only v2 added the pin_display tracking.

Note that we still retain the gist of this logic from the above commit
with the explicit force argument for the low-level clflush function.

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
---
drivers/gpu/drm/i915/i915_gem.c | 14 ++++++--------
1 file changed, 6 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index f486555fb4a8..783d1040bf83 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -39,8 +39,7 @@
#include <linux/dma-buf.h>

static void i915_gem_object_flush_gtt_write_domain(struct drm_i915_gem_object *obj);
-static void i915_gem_object_flush_cpu_write_domain(struct drm_i915_gem_object *obj,
- bool force);
+static void i915_gem_object_flush_cpu_write_domain(struct drm_i915_gem_object *obj);
static __must_check int
i915_gem_object_wait_rendering(struct drm_i915_gem_object *obj,
bool readonly);
@@ -1516,7 +1515,7 @@ i915_gem_sw_finish_ioctl(struct drm_device *dev, void *data,

/* Pinned buffers may be scanout, so flush the cache */
if (obj->pin_display)
- i915_gem_object_flush_cpu_write_domain(obj, true);
+ i915_gem_object_flush_cpu_write_domain(obj);

drm_gem_object_unreference(&obj->base);
unlock:
@@ -3680,15 +3679,14 @@ i915_gem_object_flush_gtt_write_domain(struct drm_i915_gem_object *obj)

/** Flushes the CPU write domain for the object if it's dirty. */
static void
-i915_gem_object_flush_cpu_write_domain(struct drm_i915_gem_object *obj,
- bool force)
+i915_gem_object_flush_cpu_write_domain(struct drm_i915_gem_object *obj)
{
uint32_t old_write_domain;

if (obj->base.write_domain != I915_GEM_DOMAIN_CPU)
return;

- if (i915_gem_clflush_object(obj, force))
+ if (i915_gem_clflush_object(obj, obj->pin_display))
i915_gem_chipset_flush(obj->base.dev);

old_write_domain = obj->base.write_domain;
@@ -3735,7 +3733,7 @@ i915_gem_object_set_to_gtt_domain(struct drm_i915_gem_object *obj, bool write)
if (ret)
return ret;

- i915_gem_object_flush_cpu_write_domain(obj, false);
+ i915_gem_object_flush_cpu_write_domain(obj);

/* Serialise direct access to this object with the barriers for
* coherent writes from the GPU, by effectively invalidating the
@@ -3981,7 +3979,7 @@ i915_gem_object_pin_to_display_plane(struct drm_i915_gem_object *obj,
if (ret)
goto err_unpin_display;

- i915_gem_object_flush_cpu_write_domain(obj, true);
+ i915_gem_object_flush_cpu_write_domain(obj);

old_write_domain = obj->base.write_domain;
old_read_domains = obj->base.read_domains;
--
2.1.4