Re: [PATCH 4/7] drm/i915: Disable SF pipelined attribute fetch for SNB

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

On Sat, Feb 08, 2014 at 06:28:03PM +0100, Daniel Vetter wrote:
> On Fri, Feb 07, 2014 at 12:14:47PM -0800, Kenneth Graunke wrote:
> > On 02/04/2014 11:59 AM, ville.syrjala@linux.intel.com wrote:
> > > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > > 
> > > According to Bspec we need to disable SF pipelined attribute fetch
> > > whenever SF outputs exceed 16 and normal clip mode is used. A quick
> > > glance at Mesa suggests that these conditions could happen. So let's
> > > just always set the magic bit.
> > > 
> > > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > > ---
> > >  drivers/gpu/drm/i915/i915_reg.h | 3 ++-
> > >  drivers/gpu/drm/i915/intel_pm.c | 8 ++++++++
> > >  2 files changed, 10 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> > > index 7aa2cf5..0334507 100644
> > > --- a/drivers/gpu/drm/i915/i915_reg.h
> > > +++ b/drivers/gpu/drm/i915/i915_reg.h
> > > @@ -790,7 +790,8 @@
> > >  #define _3D_CHICKEN3	0x02090
> > >  #define  _3D_CHICKEN_SF_DISABLE_OBJEND_CULL		(1 << 10)
> > >  #define  _3D_CHICKEN3_SF_DISABLE_FASTCLIP_CULL		(1 << 5)
> > > -#define  _3D_CHICKEN_SDE_LIMIT_FIFO_POLY_DEPTH(x)	((x)<<1)
> > > +#define  _3D_CHICKEN_SDE_LIMIT_FIFO_POLY_DEPTH(x)	((x)<<1) /* gen8+ */
> > > +#define  _3D_CHICKEN3_SF_DISABLE_PIPELINED_ATTR_FETCH	(1 << 1) /* gen6 */
> > >  
> > >  #define MI_MODE		0x0209c
> > >  # define VS_TIMER_DISPATCH				(1 << 6)
> > > diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> > > index 6a09281..7247084 100644
> > > --- a/drivers/gpu/drm/i915/intel_pm.c
> > > +++ b/drivers/gpu/drm/i915/intel_pm.c
> > > @@ -4683,6 +4683,14 @@ static void gen6_init_clock_gating(struct drm_device *dev)
> > >  		   _MASKED_BIT_ENABLE(_3D_CHICKEN3_SF_DISABLE_FASTCLIP_CULL));
> > >  
> > >  	/*
> > > +	 * Bspec says:
> > > +	 * "This bit must be set if 3DSTATE_CLIP clip mode is set to normal and
> > > +	 * 3DSTATE_SF number of SF output attributes is more than 16."
> > > +	 */
> > > +	I915_WRITE(_3D_CHICKEN3,
> > > +		   _MASKED_BIT_ENABLE(_3D_CHICKEN3_SF_DISABLE_PIPELINED_ATTR_FETCH));
> > > +
> > > +	/*
> > >  	 * According to the spec the following bits should be
> > >  	 * set in order to enable memory self-refresh and fbc:
> > >  	 * The bit21 and bit22 of 0x42000
> > > 
> > 
> > I'm almost positive Mesa will hit this case.  Nice catch!
> > 
> > Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
> 
> Queued for -next, thanks for the patch. Any chance that this would apply
> to one of our leftover snb gpu hang issues?

Unfortunately BSpec doesn't say what might happen if we don't set the
bit, nor did I find anything relevant in the w/a database.

-- 
Ville Syrjälä
Intel OTC