Re: [PATCH 1/2] drm/i915: reorganize the unclaimed register detection code

Daniel Vetter
2014-08-26T13:33:44Z

On Tue, Aug 26, 2014 at 10:29:23AM -0300, Paulo Zanoni wrote:
> 2014-08-26 10:18 GMT-03:00 Chris Wilson <chris@chris-wilson.co.uk>:
> > On Tue, Aug 26, 2014 at 10:04:22AM -0300, Paulo Zanoni wrote:
> >> Of course, we can also implement the one-shot thing on top of the
> >> above, but it won't really help us reducing the amount of reads on the
> >> "happy case" where we never got the error before.
> >
> > Actually I am tempted to dynamically patch the mmio vfuncs to avoid even
> > the forcewake spinlock when we already hold it. So there won't be any
> > such logic except when enabled by the user.
>
> Should I expect a patch from you, or should I go and write the patch
> based on what we already discussed?

Imo this is crazy - we have no control over what the compiler does and
when exactly it loads vtable entries, so patching them at runtime would be
an interesting excercise at best.

Adding a special version of I915_READ/WRITE for the irq hotpath makes
sense, but only if we can actually show a benefit in benchmarks.
-Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch