From mboxrd@z Thu Jan  1 00:00:00 1970
From: Chris Wilson <chris@chris-wilson.co.uk>
Subject: Re: [PATCH 05/11] drm/i915: Added debugfs support for
 PSR Status
Date: Mon, 15 Jul 2013 23:18:09 +0100
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To: Rodrigo Vivi <rodrigo.vivi@gmail.com>
Cc: intel-gfx <intel-gfx@lists.freedesktop.org>, Paulo Zanoni <paulo.r.zanoni@intel.com>
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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@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