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

[Jesse Barnes <jbarnes@virtuousgeek.org>]

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>

Thanks,
-- 
Jesse Barnes, Intel Open Source Technology Center