On Wed, 21 Mar 2012 17:19:13 -0700, Ben Widawsky <ben at bwidawsk.net> wrote:
> In theory this will have performance and power improvements. Performance
> because we don't need to stall when the scanout BO is busy, and power
> because we don't have to stall when the BO is busy ie. we can get the
> work done sooner and put the CPU to sleep (and one less interrupt
> required).
>
> Signed-off-by: Ben Widawsky <ben at bwidawsk.net>
> ---
> drivers/gpu/drm/i915/i915_gem.c | 8 +++-----
> 1 file changed, 3 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index ce2fee5..96ad162 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -3041,9 +3041,7 @@ int i915_gem_object_set_cache_level(struct drm_i915_gem_object *obj,
> * any flushes to be pipelined (for pageflips).
> *
> * For the display plane, we want to be in the GTT but out of any write
> - * domains. So in many ways this looks like set_to_gtt_domain() apart from the
> - * ability to pipeline the waits, pinning and any additional subtleties
> - * that may differentiate the display plane from ordinary buffers.
> + * domains. So in many ways this looks like set_to_gtt_domain().
...apart from the whole pinning and pipelining. It looks less like
set-to-gtt-domain over time.
Not an improvement. I'll be the first to admit that it is not a great
comment, but at least it does try to capture why we don't just treat the
display plane as GTT. A better comment would explain our concept of
display plane and pipelining.
> */
> int
> i915_gem_object_pin_to_display_plane(struct drm_i915_gem_object *obj,
> @@ -3058,8 +3056,8 @@ i915_gem_object_pin_to_display_plane(struct drm_i915_gem_object *obj,
> return ret;
>
> if (pipelined != obj->ring) {
> - ret = i915_gem_object_wait_rendering(obj);
> - if (ret == -ERESTARTSYS)
> + ret = i915_gem_object_sync(obj, pipelined);
> + if (ret)
> return ret;
> }
This looks eerily familiar.
-Chris
--
Chris Wilson, Intel Open Source Technology Centre
