From 9ad3676148511d6af72be6f3638e361fd86e1f7b Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Fri, 5 Aug 2016 10:14:21 +0100 Subject: [PATCH] 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 Reviewed-by: Joonas Lahtinen Link: http://patchwork.freedesktop.org/patch/msgid/1470388464-28458-16-git-send-email-chris@chris-wilson.co.uk --- drivers/gpu/drm/i915/i915_drv.h | 15 ++++++++------- drivers/gpu/drm/i915/i915_gem_tiling.c | 10 +++------- 2 files changed, 11 insertions(+), 14 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h index 31a614fe9ed7..f18d8761305c 100644 --- a/drivers/gpu/drm/i915/i915_drv.h +++ b/drivers/gpu/drm/i915/i915_drv.h @@ -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; diff --git a/drivers/gpu/drm/i915/i915_gem_tiling.c b/drivers/gpu/drm/i915/i915_gem_tiling.c index b7f9875f69b4..c0e01333bddf 100644 --- a/drivers/gpu/drm/i915/i915_gem_tiling.c +++ b/drivers/gpu/drm/i915/i915_gem_tiling.c @@ -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; } -- GitLab