Re: [PATCH] drm/i915: Wait up to 3ms for the pcu to ack the cdclk change request on SKL

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Thu, Jul 14, 2016 at 04:39:00PM +0200, Daniel Vetter wrote:
> On Wed, Jul 13, 2016 at 04:32:03PM +0300, ville.syrjala@linux.intel.com wrote:
> > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > 
> > Bspec tells us to keep bashing the PCU for up to 3ms when trying to
> > inform it about an upcoming change in the cdclk frequency. Currently
> > we only keep at it for 15*10usec (+ whatever delays gets added by
> > the sandybridge_pcode_read() itself). Let's change the limit to 3ms.
> > 
> > I decided to keep 10 usec delay per iteration for now, even though
> > the spec doesn't really tell us to do that.
> > 
> > Cc: David Weinehall <david.weinehall@intel.com>
> > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> Needs
> 
> Cc: stable@vger.kernel.org
> 
> and probably also a Fixes: line?

Fixes: 5d96d8afcfbb ("drm/i915/skl: Deinit/init the display at suspend/resume")

and pushed to dinq. Thanks for the review/testing.

> -Daniel
> 
> > ---
> >  drivers/gpu/drm/i915/intel_display.c | 10 +---------
> >  1 file changed, 1 insertion(+), 9 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> > index be3b2cab2640..90f26f0e2571 100644
> > --- a/drivers/gpu/drm/i915/intel_display.c
> > +++ b/drivers/gpu/drm/i915/intel_display.c
> > @@ -5691,15 +5691,7 @@ static bool skl_cdclk_pcu_ready(struct drm_i915_private *dev_priv)
> >  
> >  static bool skl_cdclk_wait_for_pcu_ready(struct drm_i915_private *dev_priv)
> >  {
> > -	unsigned int i;
> > -
> > -	for (i = 0; i < 15; i++) {
> > -		if (skl_cdclk_pcu_ready(dev_priv))
> > -			return true;
> > -		udelay(10);
> > -	}
> > -
> > -	return false;
> > +	return _wait_for(skl_cdclk_pcu_ready(dev_priv), 3000, 10) == 0;
> >  }
> >  
> >  static void skl_set_cdclk(struct drm_i915_private *dev_priv, int cdclk, int vco)
> > -- 
> > 2.7.4
> > 
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx@lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/intel-gfx
> 
> -- 
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch

-- 
Ville Syrjälä
Intel OTC
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