Re: [PATCH 2/7] drm/i915: Resolving the memory region conflict for Stolen area

[Jesse Barnes <jbarnes@virtuousgeek.org>]

On Thu, 27 Feb 2014 11:01:08 +0200
Jani Nikula <jani.nikula@linux.intel.com> wrote:

> On Thu, 27 Feb 2014, Jani Nikula <jani.nikula@linux.intel.com> wrote:
> > On Wed, 26 Feb 2014, Jesse Barnes <jbarnes@virtuousgeek.org> wrote:
> >> On Mon, 13 Jan 2014 16:25:21 +0530
> >> akash.goel@intel.com wrote:
> >>
> >>> From: Akash Goel <akash.goel@intel.com>
> >>> 
> >>> There is a conflict seen when requesting the kernel to reserve
> >>> the physical space used for the stolen area. This is because
> >>> some BIOS are wrapping the stolen area in the root PCI bus, but have
> >>> an off-by-one error. As a workaround we retry the reservation with an
> >>> offset of 1 instead of 0.
> >>> 
> >>> v2: updated commit message & the comment in source file (Daniel)
> >>> 
> >>> Signed-off-by: Akash Goel <akash.goel@intel.com>
> >>> ---
> >>>  drivers/gpu/drm/i915/i915_gem_stolen.c | 20 +++++++++++++++++---
> >>>  1 file changed, 17 insertions(+), 3 deletions(-)
> >>> 
> >>> diff --git a/drivers/gpu/drm/i915/i915_gem_stolen.c b/drivers/gpu/drm/i915/i915_gem_stolen.c
> >>> index 1a24e84..114a806 100644
> >>> --- a/drivers/gpu/drm/i915/i915_gem_stolen.c
> >>> +++ b/drivers/gpu/drm/i915/i915_gem_stolen.c
> >>> @@ -82,9 +82,23 @@ static unsigned long i915_stolen_to_physical(struct drm_device *dev)
> >>>  	r = devm_request_mem_region(dev->dev, base, dev_priv->gtt.stolen_size,
> >>>  				    "Graphics Stolen Memory");
> >>>  	if (r == NULL) {
> >>> -		DRM_ERROR("conflict detected with stolen region: [0x%08x - 0x%08x]\n",
> >>> -			  base, base + (uint32_t)dev_priv->gtt.stolen_size);
> >>> -		base = 0;
> >>> +		/*
> >>> +		 * One more attempt but this time requesting region from
> >>> +		 * base + 1, as we have seen that this resolves the region
> >>> +		 * conflict with the PCI Bus.
> >>> +		 * This is a BIOS w/a: Some BIOS wrap stolen in the root
> >>> +		 * PCI bus, but have an off-by-one error. Hence retry the
> >>> +		 * reservation starting from 1 instead of 0.
> >>> +		 */
> >>> +		r = devm_request_mem_region(dev->dev, base + 1,
> >>> +					    dev_priv->gtt.stolen_size - 1,
> >>> +					    "Graphics Stolen Memory");
> >>> +		if (r == NULL) {
> >>> +			DRM_ERROR("conflict detected with stolen region:"\
> >>> +				  "[0x%08x - 0x%08x]\n",
> >>> +				  base, base + (uint32_t)dev_priv->gtt.stolen_size);
> >>> +			base = 0;
> >>> +		}
> >>>  	}
> >>>  
> >>>  	return base;
> >>
> >> Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
> >> Tested-by: Arjan van de Ven <arjan@linux.intel.com>
> >
> > Pushed to -fixes, thanks for the patch, review, and testing.
> 
> Oh, forgot to add that I fixed the DRM_ERROR string split up that
> checkpatch complained about while applying.

Note I think we should do this at the x86 quirk level as well since
otherwise the kernel may put MMIO space on top of our stolen range.

-- 
Jesse Barnes, Intel Open Source Technology Center