[Intel-gfx] [PATCH 05/11] drm/i915: Added debugfs support for PSR Status

[Chris Wilson]

On Mon, Jul 15, 2013 at 05:13:27PM -0300, Rodrigo Vivi wrote:
> On Mon, Jul 15, 2013 at 11:03 AM, Chris Wilson <chris at chris-wilson.co.uk> wrote:
> >> +             seq_puts(m, "PSR not supported on this platform\n");
> >> +             return 0;
> >> +     }
> >> +
> >> +     psrctl = I915_READ(EDP_PSR_CTL);
> >
> > Missing locking.
> 
> what lock? that psr exit is on debug_ctl

I wanted to serialise the read of EDP_PSR_CTL against the write after a
modeset. It should not be strictly necessary in this debug context.

(However, we now have very strict rules that imply concurrent access to
registers (within the same cacheline, even) is verboten.)
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre