Massive power regression going 3.4->3.5

[James Bottomley]

On Tue, 2012-07-31 at 20:24 +0100, Chris Wilson wrote:
> On Tue, 31 Jul 2012 11:14:17 +0100, Chris Wilson <chris at chris-wilson.co.uk> wrote:
> > On Tue, 31 Jul 2012 10:57:10 +0100, James Bottomley <James.Bottomley at HansenPartnership.com> wrote:
> > > > When did you inspect the debug files? One effect I can imagine is that
> > > > if your system was previously stuck at RPn and never upclocking the GPU
> > > > when X starts. The question would then be what is preventing the GPU
> > > > from reaching its lowest power state again.
> > > 
> > > After I logged into an xfce4 session and powertop showed idle had been
> > > reached.
> 
> That you are using xfce4 makes the use of semaphores for pageflips as
> being the root cause even more suspect. Pageflips are only used for a
> fullscreen DRI client caalling SwapBuffers, to my knowledge xfce4 does
> not use DRI at all - its compositing manager is XRender based if you
> happen to be using it.
> 
> Please can you try the small patch to disable the use of semaphores for
> pageflips and see if the regression remains (which I judge it will...):
> 
> diff --git a/drivers/gpu/drm/i915/i915_gem.c
> b/drivers/gpu/drm/i915/i915_gem.c
> index 5c4657a..f301f2f 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -3067,7 +3067,7 @@ i915_gem_object_pin_to_display_plane(struct drm_i915_gem_o
>                 return ret;
>  
>         if (pipelined != obj->ring) {
> -               ret = i915_gem_object_sync(obj, pipelined);
> +               ret = i915_gem_object_wait_rendering(obj);
>                 if (ret)
>                         return ret;
>         }

Your patch doesn't apply ... I think because in v3.5 this line is
displaced by about 200 lines in the file.

patching file drivers/gpu/drm/i915/i915_gem.c
Hunk #1 FAILED at 3067.
1 out of 1 hunk FAILED -- saving rejects to file
drivers/gpu/drm/i915/i915_gem.c.rej

I got the attached to apply and it doesn't really improve the idle power
much (12.5W).

James

---

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 288d7b8..2f3f279 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2869,7 +2869,7 @@ i915_gem_object_pin_to_display_plane(struct drm_i915_gem_object *obj,
 		return ret;
 
 	if (pipelined != obj->ring) {
-		ret = i915_gem_object_sync(obj, pipelined);
+		ret = i915_gem_object_wait_rendering(obj);
 		if (ret)
 			return ret;
 	}