Re: [PATCH v2] drm/i915: Fix PIPE_CONTROL DW/QW write through global GTT on IVB+

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

On Tue, Feb 19, 2013 at 03:59:16PM -0800, Ben Widawsky wrote:
> On Thu, Feb 14, 2013 at 02:46:44PM -0800, Ben Widawsky wrote:
> > On Thu, Feb 14, 2013 at 09:53:51PM +0200, ville.syrjala@linux.intel.com wrote:
> > > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > > 
> > > The bit controlling whether PIPE_CONTROL DW/QW write targets
> > > the global GTT or PPGTT moved moved from DW 2 bit 2 to
> > > DW 1 bit 24 on IVB.
> > > 
> > > I verified on IVB that the fix is in fact effective. Without the fix
> > > none of the scratch writes actually landed in the pipe control page.
> > > With the fix the writes show up correctly.
> > > 
> > > v2: move PIPE_CONTROL_GLOBAL_GTT_IVB setup to where other flags are set
> > > 
> > > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > Reviewed-by: Ben Widawsky <ben@bwidawsk.net>
> > [snip]
> 
> Reading the bspec again... do we want to set bit 21?

I don't think we want to do that. The scratch address we're using here
is a proper GTT address, not an index into the HWS page.

I have no idea why we're not using the HSW page here as well. I couldn't
dig out any reason from the commit logs either. Anyone?

-- 
Ville Syrjälä
Intel OTC