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drm/i915: Remove locking for get_tiling 

Since we are not concerned with userspace racing itself with set-tiling
(the order is indeterminant even if we take a lock), then we can safely
read back the single obj->tiling_mode and do the static lookup of
swizzle mode without having to take a lock.

get-tiling is reasonably frequent due to the back-channel passing around
of tiling parameters in DRI2/DRI3.

v2: Make tiling_mode a full unsigned int so that we can trivially use it
with READ_ONCE(). Separating it out into manual control over the flags
field was too noisy for a simple patch. Note that we could use the lower
bits of obj->stride for the tiling mode.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1470388464-28458-16-git-send-email-chris@chris-wilson.co.uk
This commit is contained in:
Chris Wilson 2016-08-05 10:14:21 +01:00
parent e883d73503
commit 9ad3676148
2 changed files with 11 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
drivers/gpu/drm/i915/i915_drv.h
View File

@ -2182,10 +2182,6 @@ struct drm_i915_gem_object {
*/
unsigned int madv:2;
/**
* Current tiling mode for the object.
*/
unsigned int tiling_mode:2;
/**
* Whether the tiling parameters for the currently associated fence
* register have changed. Note that for the purposes of tracking
@ -2218,6 +2214,14 @@ struct drm_i915_gem_object {
atomic_t frontbuffer_bits;
/**
* Current tiling mode for the object.
*/
unsigned int tiling_mode;
/** Current tiling stride for the object, if it's tiled. */
uint32_t stride;
unsigned int has_wc_mmap;
/** Count of VMA actually bound by this object */
unsigned int bind_count;
@ -2245,9 +2249,6 @@ struct drm_i915_gem_object {
struct i915_gem_active last_write;
struct i915_gem_active last_fence;
/** Current tiling stride for the object, if it's tiled. */
uint32_t stride;
/** References from framebuffers, locks out tiling changes. */
unsigned long framebuffer_references;

10
drivers/gpu/drm/i915/i915_gem_tiling.c
View File

@ -303,10 +303,8 @@ i915_gem_get_tiling(struct drm_device *dev, void *data,
if (!obj)
return -ENOENT;
mutex_lock(&dev->struct_mutex);
args->tiling_mode = obj->tiling_mode;
switch (obj->tiling_mode) {
args->tiling_mode = READ_ONCE(obj->tiling_mode);
switch (args->tiling_mode) {
case I915_TILING_X:
args->swizzle_mode = dev_priv->mm.bit_6_swizzle_x;
break;
@ -330,8 +328,6 @@ i915_gem_get_tiling(struct drm_device *dev, void *data,
if (args->swizzle_mode == I915_BIT_6_SWIZZLE_9_10_17)
args->swizzle_mode = I915_BIT_6_SWIZZLE_9_10;
i915_gem_object_put(obj);
mutex_unlock(&dev->struct_mutex);
i915_gem_object_put_unlocked(obj);
return 0;
}