[Intel-gfx] [PATCH] drm/agp/i915: trim stolen space to 32M

[Simon Farnsworth]

On Wednesday 7 July 2010, Jesse Barnes <jbarnes at virtuousgeek.org> wrote:
> Some BIOSes will claim a large chunk of stolen space.  Unless we
> reclaim it, our aperture for remapping buffer objects will be
> constrained.  So clamp the stolen space to 32M and ignore the rest.
> 
I'm not sure that this changelog fits the patch - if I'm understanding the code 
correctly, you're clamping to 16M, not 32M.

Apart from that, the code looks sensible.

> diff --git a/drivers/char/agp/intel-gtt.c b/drivers/char/agp/intel-gtt.c
> index f97122a..54ed0e1 100644
> --- a/drivers/char/agp/intel-gtt.c
> +++ b/drivers/char/agp/intel-gtt.c
> @@ -25,6 +25,10 @@
>  #define USE_PCI_DMA_API 1
>  #endif
> 
> +/* Max amount of stolen space, anything above will be returned to Linux */
> +int intel_max_stolen = 16 * 1024 * 1024;

This is 16M, not 32M

> +EXPORT_SYMBOL(intel_max_stolen);
> +
>  static const struct aper_size_info_fixed intel_i810_sizes[] =
>  {
>  	{64, 16384, 4},
> @@ -710,7 +714,12 @@ static void intel_i830_init_gtt_entries(void)
>  			break;
>  		}
>  	}
> -	if (gtt_entries > 0) {
> +	if (!local && gtt_entries > intel_max_stolen) {
> +		dev_info(&agp_bridge->dev->dev,
> +			 "detected %dK stolen memory, trimming to %dK\n",
> +			 gtt_entries / KB(1), intel_max_stolen / KB(1));
> +		gtt_entries = intel_max_stolen / KB(4);

This appears to limit to intel_max_stolen bytes, not intel_max_stolen * 2 
bytes.

> +	} else if (gtt_entries > 0) {
>  		dev_info(&agp_bridge->dev->dev, "detected %dK %s memory\n",
>  		       gtt_entries / KB(1), local ? "local" : "stolen");
>  		gtt_entries /= KB(4);
> diff --git a/drivers/gpu/drm/i915/i915_dma.c
> b/drivers/gpu/drm/i915/i915_dma.c index e2dd903..69e25ab 100644
> --- a/drivers/gpu/drm/i915/i915_dma.c
> +++ b/drivers/gpu/drm/i915/i915_dma.c
> @@ -40,6 +40,8 @@
>  #include <linux/vga_switcheroo.h>
>  #include <linux/slab.h>
> 
> +extern int intel_max_stolen; /* from AGP driver */
> +
>  /**
>   * Sets up the hardware status page for devices that need a physical
> address * in the register.
> @@ -2105,6 +2107,12 @@ int i915_driver_load(struct drm_device *dev,
> unsigned long flags) if (ret)
>  		goto out_iomapfree;
> 
> +	if (prealloc_size > intel_max_stolen) {
> +		DRM_INFO("detected %dM stolen memory, trimming to %dM\n",
> +			 prealloc_size >> 20, intel_max_stolen >> 20);
> +		prealloc_size = intel_max_stolen;

And again here, you appear to limit to intel_max_stolen, not to twice that.

> +	}
> +
>  	dev_priv->wq = create_singlethread_workqueue("i915");
>  	if (dev_priv->wq == NULL) {
>  		DRM_ERROR("Failed to create our workqueue.\n");
-- 
Simon Farnsworth
Software Engineer
ONELAN Limited
http://www.onelan.com/