[Intel-gfx] [PATCH 04/37] drm/i915: rework locking for intel_dpio|sbi_read|write

[Daniel Vetter]

On Wed, Dec 12, 2012 at 12:54:47PM -0800, Jesse Barnes wrote:
> On Wed, 12 Dec 2012 14:06:44 +0100
> Daniel Vetter <daniel.vetter at ffwll.ch> wrote:
> 
> > Spinning for up to 200 us with interrupts locked out is not good. So
> > let's just spin (and even that seems to be excessive).
> > 
> > And we don't call these functions from interrupt context, so this is
> > not required. Besides that doing anything in interrupt contexts which
> > might take a few hundred us is a no-go. So just convert the entire
> > thing to a mutex. Also move the mutex-grabbing out of the read/write
> > functions (add a WARN_ON(!is_locked)) instead) since all callers are
> > nicely grouped together.
> > 
> > Finally the real motivation for this change: Dont grab the modeset
> > mutex in the dpio debugfs file, we don't need that consistency. And
> > correctness of the dpio interface is ensured with the dpio_lock.
> > 
> > Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch>
> 
> Looks fine, I guess you could convert the wait_for_atomic_us to the
> non-atomic variant now that you have a mutex.  Either way:

I like that _us purely to document the correct timeout ...

> Reviewed-by: Jesse Barnes <jbarnes at virtuousgeek.org>

Queued for -next, thanks for the review.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch