[Intel-gfx] [PATCH v2] drm/i915: DMA map DSM [stolen memory]

[Chris Wilson]

Pass the physical address of our BIOS reserved stolen memory to the dma
mapper so we convert it into a proper dma_addr_t and track access with
the iommu.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/gem/i915_gem_stolen.c | 29 +++++++++++++++++++++-
 drivers/gpu/drm/i915/i915_drv.h            |  5 ++++
 2 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_stolen.c b/drivers/gpu/drm/i915/gem/i915_gem_stolen.c
index 0be5e8683337..376b9ecd405a 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_stolen.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_stolen.c
@@ -162,6 +162,12 @@ static void i915_gem_cleanup_stolen(struct drm_i915_private *i915)
 	if (!drm_mm_initialized(&i915->mm.stolen))
 		return;
 
+	if (i915->dsm_dma != i915->dsm.start)
+		dma_unmap_resource(i915->drm.dev,
+				   i915->dsm_dma, resource_size(&i915->dsm),
+				   DMA_BIDIRECTIONAL,
+				   DMA_ATTR_NO_WARN);
+
 	drm_mm_takedown(&i915->mm.stolen);
 }
 
@@ -372,6 +378,18 @@ static void icl_get_stolen_reserved(struct drm_i915_private *i915,
 	}
 }
 
+static dma_addr_t remap_stolen(struct drm_i915_private *i915)
+{
+	if (pfn_valid(PHYS_PFN(i915->dsm.start)))
+		return (dma_addr_t)i915->dsm.start;
+
+	return dma_map_resource(i915->drm.dev,
+				i915->dsm.start, resource_size(&i915->dsm),
+				DMA_BIDIRECTIONAL,
+				DMA_ATTR_NO_KERNEL_MAPPING |
+				DMA_ATTR_SKIP_CPU_SYNC);
+}
+
 static int i915_gem_init_stolen(struct drm_i915_private *i915)
 {
 	struct intel_uncore *uncore = &i915->uncore;
@@ -489,6 +507,14 @@ static int i915_gem_init_stolen(struct drm_i915_private *i915)
 	i915->stolen_usable_size =
 		resource_size(&i915->dsm) - reserved_total;
 
+	i915->dsm_dma = remap_stolen(i915);
+	if (dma_mapping_error(i915->drm.dev, i915->dsm_dma)) {
+		drm_err(&i915->drm,
+			"Failed to map stolen memory %pR for use with DMA\n",
+			&i915->dsm);
+		return 0; /* bail; continue to load the driver without stolen */
+	}
+
 	/* Basic memrange allocator for stolen space. */
 	drm_mm_init(&i915->mm.stolen, 0, i915->stolen_usable_size);
 
@@ -504,6 +530,7 @@ i915_pages_create_for_stolen(struct drm_device *dev,
 	struct scatterlist *sg;
 
 	GEM_BUG_ON(range_overflows(offset, size, resource_size(&i915->dsm)));
+	GEM_BUG_ON(dma_mapping_error(dev->dev, i915->dsm_dma));
 
 	/* We hide that we have no struct page backing our stolen object
 	 * by wrapping the contiguous physical allocation with a fake
@@ -523,7 +550,7 @@ i915_pages_create_for_stolen(struct drm_device *dev,
 	sg->offset = 0;
 	sg->length = size;
 
-	sg_dma_address(sg) = (dma_addr_t)i915->dsm.start + offset;
+	sg_dma_address(sg) = i915->dsm_dma + offset;
 	sg_dma_len(sg) = size;
 
 	return st;
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 9c2672c56cc1..44972eda7fb8 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -836,6 +836,11 @@ struct drm_i915_private {
 	 */
 	struct resource dsm_reserved;
 
+	/**
+	 * dma-mapping of the Data Stolen Memory.
+	 */
+	dma_addr_t dsm_dma;
+
 	/*
 	 * Stolen memory is segmented in hardware with different portions
 	 * offlimits to certain functions.
-- 
2.20.1