Re: [PATCH v2 5/6] drm/i915: Don't clobber the GTT when it's within stolen memory

[Jani Nikula <jani.nikula@linux.intel.com>]

On Thu, 05 Jun 2014, ville.syrjala@linux.intel.com wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
>
> On most gen2-4 platforms the GTT can be (or maybe always is?)
> inside the stolen memory region. If that's the case, reduce the
> size of the stolen memory appropriately to make make sure we
> don't clobber the GTT.
>
> v2: Deal with gen4 36 bit physical address

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=80151

> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/i915_gem_stolen.c | 44 ++++++++++++++++++++++++++++++++++
>  drivers/gpu/drm/i915/i915_reg.h        |  3 +++
>  2 files changed, 47 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem_stolen.c b/drivers/gpu/drm/i915/i915_gem_stolen.c
> index 62ef55b..7465ab0 100644
> --- a/drivers/gpu/drm/i915/i915_gem_stolen.c
> +++ b/drivers/gpu/drm/i915/i915_gem_stolen.c
> @@ -74,6 +74,50 @@ static unsigned long i915_stolen_to_physical(struct drm_device *dev)
>  	if (base == 0)
>  		return 0;
>  
> +	/* make sure we don't clobber the GTT if it's within stolen memory */
> +	if (INTEL_INFO(dev)->gen <= 4 && !IS_G33(dev) && !IS_G4X(dev)) {
> +		struct {
> +			u32 start, end;
> +		} stolen[2] = {
> +			{ .start = base, .end = base + dev_priv->gtt.stolen_size, },
> +			{ .start = base, .end = base + dev_priv->gtt.stolen_size, },
> +		};
> +		u64 gtt_start, gtt_end;
> +
> +		gtt_start = I915_READ(PGTBL_CTL);
> +		if (IS_GEN4(dev))
> +			gtt_start = (gtt_start & PGTBL_ADDRESS_LO_MASK) |
> +				(gtt_start & PGTBL_ADDRESS_HI_MASK) << 28;
> +		else
> +			gtt_start &= PGTBL_ADDRESS_LO_MASK;
> +		gtt_end = gtt_start + gtt_total_entries(dev_priv->gtt) * 4;
> +
> +		if (gtt_start >= stolen[0].start && gtt_start < stolen[0].end)
> +			stolen[0].end = gtt_start;
> +		if (gtt_end > stolen[1].start && gtt_end <= stolen[1].end)
> +			stolen[1].start = gtt_end;
> +
> +		/* pick the larger of the two chunks */
> +		if (stolen[0].end - stolen[0].start >
> +		    stolen[1].end - stolen[1].start) {
> +			base = stolen[0].start;
> +			dev_priv->gtt.stolen_size = stolen[0].end - stolen[0].start;
> +		} else {
> +			base = stolen[1].start;
> +			dev_priv->gtt.stolen_size = stolen[1].end - stolen[1].start;
> +		}
> +
> +		if (stolen[0].start != stolen[1].start ||
> +		    stolen[0].end != stolen[1].end) {
> +			DRM_DEBUG_KMS("GTT within stolen memory at 0x%llx-0x%llx\n",
> +				      (unsigned long long) gtt_start,
> +				      (unsigned long long) gtt_end - 1);
> +			DRM_DEBUG_KMS("Stolen memory adjusted to 0x%x-0x%x\n",
> +				      base, base + (u32) dev_priv->gtt.stolen_size - 1);
> +		}
> +	}
> +
> +
>  	/* Verify that nothing else uses this physical address. Stolen
>  	 * memory should be reserved by the BIOS and hidden from the
>  	 * kernel. So if the region is already marked as busy, something
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index 247be2a..619924b 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -978,6 +978,9 @@ enum punit_power_well {
>  /*
>   * Instruction and interrupt control regs
>   */
> +#define PGTBL_CTL	0x02020
> +#define   PGTBL_ADDRESS_LO_MASK	0xfffff000 /* bits [31:12] */
> +#define   PGTBL_ADDRESS_HI_MASK	0x000000f0 /* bits [35:32] (gen4) */
>  #define PGTBL_ER	0x02024
>  #define RENDER_RING_BASE	0x02000
>  #define BSD_RING_BASE		0x04000
> -- 
> 1.8.5.5
>
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-- 
Jani Nikula, Intel Open Source Technology Center
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