diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c index 22ad9c3881214363741887391b284ef6d886768d..f48d8454f0efb0b7b82d59a4a5792fb066cbc05b 100644 --- a/drivers/gpu/drm/i915/i915_gem_gtt.c +++ b/drivers/gpu/drm/i915/i915_gem_gtt.c @@ -2253,7 +2253,17 @@ static int ggtt_probe_common(struct drm_device *dev, gtt_phys_addr = pci_resource_start(dev->pdev, 0) + (pci_resource_len(dev->pdev, 0) / 2); - dev_priv->gtt.gsm = ioremap_wc(gtt_phys_addr, gtt_size); + /* + * On BXT writes larger than 64 bit to the GTT pagetable range will be + * dropped. For WC mappings in general we have 64 byte burst writes + * when the WC buffer is flushed, so we can't use it, but have to + * resort to an uncached mapping. The WC issue is easily caught by the + * readback check when writing GTT PTE entries. + */ + if (IS_BROXTON(dev)) + dev_priv->gtt.gsm = ioremap_nocache(gtt_phys_addr, gtt_size); + else + dev_priv->gtt.gsm = ioremap_wc(gtt_phys_addr, gtt_size); if (!dev_priv->gtt.gsm) { DRM_ERROR("Failed to map the gtt page table\n"); return -ENOMEM;