Re: [PATCH] drm/i915: fix sanitize_enable_ppgtt for full PPGTT

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

On Wed, Jun 25, 2014 at 03:45:33PM -0700, Jesse Barnes wrote:
> Apparently trinary logic is hard.  We were falling through all the forced
> cases and simply enabling aliasing PPGTT or not based on hardware,
> rather than full PPGTT if available.
> 
> References: https://bugs.freedesktop.org/show_bug.cgi?id=80083
> Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
> ---
>  drivers/gpu/drm/i915/i915_gem_gtt.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
> index a4153ee..86521a7 100644
> --- a/drivers/gpu/drm/i915/i915_gem_gtt.c
> +++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
> @@ -69,7 +69,13 @@ static int sanitize_enable_ppgtt(struct drm_device *dev, int enable_ppgtt)
>  		return 0;
>  	}
>  
> -	return HAS_ALIASING_PPGTT(dev) ? 1 : 0;
> +	/* Fall through to auto-detect */
> +	if (HAS_PPGTT(dev))
> +		return 2;
> +	else if (HAS_ALIASING_PPGTT(dev))
> +		return 1;
> +
> +	return 0;

I don't get it. This would just enable full ppgtt by default. But full
ppgtt is still a bit broken so I don't think we want this.

The dmesg in the bug shows that ppgtt was forced off by the PCI revision
check, so that part seems to have worked. Looks like the tests doesn't
expect the batches to be accepted by the kernel, but the cmd parser is
bypassed when ppgtt is disabled, so the test fails.

-- 
Ville Syrjälä
Intel OTC