Re: [PATCH 2/2] drm/i915: Remove open-coded callers of flush_cpu_write_domain

Ville Syrjälä
2015-01-21T14:12:11Z

On Wed, Jan 21, 2015 at 02:53:49PM +0100, Daniel Vetter wrote:
> Both places check the cpu domain and through some indirection
> obj->pin_display and whether cpu access is coherent. And then flush
> both cpu caches and the chipset cache. Which is what
> flush_cpu_write_domain does.
>
> Only difference is that on top we get a tracepoint, frontbuffer
> tracking and and domain tracking updates. Which doesn't matter since
> both paths are slowpaths.
>
> So lets go with more shared code for clearer idioms.
>
> 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 | 15 ++++-----------
> 1 file changed, 4 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index 783d1040bf83..b48c39230b80 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -1019,11 +1019,8 @@ out:
> * cachelines in-line while writing and the object moved
> * out of the cpu write domain while we've dropped the lock.
> */
> - if (!needs_clflush_after &&
> - obj->base.write_domain != I915_GEM_DOMAIN_CPU) {
> - if (i915_gem_clflush_object(obj, obj->pin_display))
> - i915_gem_chipset_flush(dev);
> - }
> + if (!needs_clflush_after)
> + i915_gem_object_flush_cpu_write_domain(obj);

Nack. You've just inverted the write domain check.

> }
>
> if (needs_clflush_after)
> @@ -3825,12 +3822,8 @@ int i915_gem_object_set_cache_level(struct drm_i915_gem_object *obj,
> vma->node.color = cache_level;
> obj->cache_level = cache_level;
>
> - if (obj->cache_dirty &&
> - obj->base.write_domain != I915_GEM_DOMAIN_CPU &&
> - cpu_write_needs_clflush(obj)) {
> - if (i915_gem_clflush_object(obj, true))
> - i915_gem_chipset_flush(obj->base.dev);
> - }
> + if (obj->cache_dirty)
> + i915_gem_object_flush_cpu_write_domain(obj);
>
> return 0;
> }
> --
> 2.1.4

--
Ville Syrjälä
Intel OTC