Re: [PATCH 2/2] drm/i915: Fix GT wake FIFO free entries for VLV

[Daniel Vetter <daniel@ffwll.ch>]

On Wed, Nov 27, 2013 at 09:04:38AM -0800, Jesse Barnes wrote:
> On Thu, 14 Nov 2013 02:00:00 +0200
> ville.syrjala@linux.intel.com wrote:
> 
> > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > 
> > On VLV the GTFIFOCTL register has other bits besides the number of free
> > entries in the GT wake FIFO. Apply a mask when we read th register to
> > make sure we don't misinterpret the number of free FIFO entries.
> > 
> > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > ---
> >  drivers/gpu/drm/i915/i915_reg.h     | 3 ++-
> >  drivers/gpu/drm/i915/intel_uncore.c | 6 +++---
> >  2 files changed, 5 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> > index e8f47de..e243105 100644
> > --- a/drivers/gpu/drm/i915/i915_reg.h
> > +++ b/drivers/gpu/drm/i915/i915_reg.h
> > @@ -4860,7 +4860,8 @@
> >  #define    GT_FIFO_IAWRERR			(1<<1)
> >  #define    GT_FIFO_IARDERR			(1<<0)
> >  
> > -#define  GT_FIFO_FREE_ENTRIES			0x120008
> > +#define  GTFIFOCTL				0x120008
> > +#define    GT_FIFO_FREE_ENTRIES_MASK		0x7f
> >  #define    GT_FIFO_NUM_RESERVED_ENTRIES		20
> >  
> >  #define  HSW_IDICR				0x9008
> > diff --git a/drivers/gpu/drm/i915/intel_uncore.c b/drivers/gpu/drm/i915/intel_uncore.c
> > index a9849ab..71902c4 100644
> > --- a/drivers/gpu/drm/i915/intel_uncore.c
> > +++ b/drivers/gpu/drm/i915/intel_uncore.c
> > @@ -148,10 +148,10 @@ static int __gen6_gt_wait_for_fifo(struct drm_i915_private *dev_priv)
> >  
> >  	if (dev_priv->uncore.fifo_count < GT_FIFO_NUM_RESERVED_ENTRIES) {
> >  		int loop = 500;
> > -		u32 fifo = __raw_i915_read32(dev_priv, GT_FIFO_FREE_ENTRIES);
> > +		u32 fifo = __raw_i915_read32(dev_priv, GTFIFOCTL) & GT_FIFO_FREE_ENTRIES_MASK;
> >  		while (fifo <= GT_FIFO_NUM_RESERVED_ENTRIES && loop--) {
> >  			udelay(10);
> > -			fifo = __raw_i915_read32(dev_priv, GT_FIFO_FREE_ENTRIES);
> > +			fifo = __raw_i915_read32(dev_priv, GTFIFOCTL) & GT_FIFO_FREE_ENTRIES_MASK;
> >  		}
> >  		if (WARN_ON(loop < 0 && fifo <= GT_FIFO_NUM_RESERVED_ENTRIES))
> >  			++ret;
> > @@ -806,7 +806,7 @@ static int gen6_do_reset(struct drm_device *dev)
> >  		dev_priv->uncore.funcs.force_wake_put(dev_priv);
> >  
> >  	/* Restore fifo count */
> > -	dev_priv->uncore.fifo_count = __raw_i915_read32(dev_priv, GT_FIFO_FREE_ENTRIES);
> > +	dev_priv->uncore.fifo_count = __raw_i915_read32(dev_priv, GTFIFOCTL) & GT_FIFO_FREE_ENTRIES_MASK;
> >  
> >  	spin_unlock_irqrestore(&dev_priv->uncore.lock, irqflags);
> >  	return ret;
> 
> I don't see this reg on HSW, but it looks like our HSW code uses this
> routine?
> 
> Assuming the spec is just broken today... at least I see it for other
> gens.
> 
> Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>

Both merged with a little note about this one here. We can back it out
again ;-)

Thanks, Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch