[PATCH 1/2] ACPI/IORT: add iort_get_memory_address_limit function

[PATCH 1/2] ACPI/IORT: add iort_get_memory_address_limit function

[Nate Watterson]

The memory_address_limit field present in IORT named component nodes
describes the effective number of address bits that a device can use
when accessing memory. Because this information has value when creating
or validating device dma_masks, the aforementioned accessor function is
introduced.

Signed-off-by: Nate Watterson <nwatters@codeaurora.org>
---
 drivers/acpi/arm64/iort.c | 25 +++++++++++++++++++++++++
 include/linux/acpi_iort.h |  3 +++
 2 files changed, 28 insertions(+)

diff --git a/drivers/acpi/arm64/iort.c b/drivers/acpi/arm64/iort.c
index e0d2e6e..cd5d5f4 100644
--- a/drivers/acpi/arm64/iort.c
+++ b/drivers/acpi/arm64/iort.c
@@ -569,6 +569,31 @@ void iort_set_dma_mask(struct device *dev)
 }
 
 /**
+ * iort_get_memory_address_limit - If a named component node exists in the IORT
+ *                                 for a device, get the number of address bits
+ *                                 that the device can effectively use when
+ *                                 accessing memory.
+ *
+ * @dev: The device
+ *
+ * Returns: ENOENT when no corresponding named component node found for dev
+ *          Named component memory_address_limit field otherwise
+ */
+int iort_get_memory_address_limit(struct device *dev)
+{
+	struct acpi_iort_node *node;
+	struct acpi_iort_named_component *ncomp;
+
+	node = iort_scan_node(ACPI_IORT_NODE_NAMED_COMPONENT,
+			      iort_match_node_callback, dev);
+	if (!node)
+		return -ENOENT;
+
+	ncomp = (struct acpi_iort_named_component *)node->node_data;
+	return ncomp->memory_address_limit;
+}
+
+/**
  * iort_iommu_configure - Set-up IOMMU configuration for a device.
  *
  * @dev: device to configure
diff --git a/include/linux/acpi_iort.h b/include/linux/acpi_iort.h
index 77e0809..677b9c4 100644
--- a/include/linux/acpi_iort.h
+++ b/include/linux/acpi_iort.h
@@ -36,6 +36,7 @@
 struct irq_domain *iort_get_device_domain(struct device *dev, u32 req_id);
 /* IOMMU interface */
 void iort_set_dma_mask(struct device *dev);
+int iort_get_memory_address_limit(struct device *dev);
 const struct iommu_ops *iort_iommu_configure(struct device *dev);
 #else
 static inline void acpi_iort_init(void) { }
@@ -47,6 +48,8 @@ static inline struct irq_domain *iort_get_device_domain(struct device *dev,
 { return NULL; }
 /* IOMMU interface */
 static inline void iort_set_dma_mask(struct device *dev) { }
+static inline int iort_get_memory_address_limit(struct device *dev)
+{ return -ENOENT; }
 static inline
 const struct iommu_ops *iort_iommu_configure(struct device *dev)
 { return NULL; }
-- 
Qualcomm Datacenter Technologies, Inc. on behalf of Qualcomm Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux
Foundation Collaborative Project.

[PATCH 2/2] arm64/dma-mapping: validate dma_masks against IORT defined limits

[Nate Watterson]

Some drivers set the dma_mask of client devices based solely on values
read from capability registers which may not account for platform
specific bus address width limitations. Fortunately, the ACPI IORT table
provides a way to report the effective number of address bits a device
can use to access memory. This information, when present, is used to
supplement the checks already being done in dma_supported() to avoid
setting overly generous dma_masks.

Signed-off-by: Nate Watterson <nwatters@codeaurora.org>
---
 arch/arm64/mm/dma-mapping.c | 20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c
index e040827..467fd23 100644
--- a/arch/arm64/mm/dma-mapping.c
+++ b/arch/arm64/mm/dma-mapping.c
@@ -19,6 +19,7 @@
 
 #include <linux/gfp.h>
 #include <linux/acpi.h>
+#include <linux/acpi_iort.h>
 #include <linux/bootmem.h>
 #include <linux/cache.h>
 #include <linux/export.h>
@@ -347,6 +348,12 @@ static int __swiotlb_get_sgtable(struct device *dev, struct sg_table *sgt,
 
 static int __swiotlb_dma_supported(struct device *hwdev, u64 mask)
 {
+	int dma_limit;
+
+	dma_limit = iort_get_memory_address_limit(hwdev);
+	if (dma_limit >= 0 && DMA_BIT_MASK(dma_limit) < mask)
+		return 0;
+
 	if (swiotlb)
 		return swiotlb_dma_supported(hwdev, mask);
 	return 1;
@@ -784,6 +791,17 @@ static void __iommu_unmap_sg_attrs(struct device *dev,
 	iommu_dma_unmap_sg(dev, sgl, nelems, dir, attrs);
 }
 
+static int __iommu_dma_supported(struct device *hwdev, u64 mask)
+{
+	int dma_limit;
+
+	dma_limit = iort_get_memory_address_limit(hwdev);
+	if (dma_limit >= 0 && DMA_BIT_MASK(dma_limit) < mask)
+		return 0;
+
+	return iommu_dma_supported(hwdev, mask);
+}
+
 static struct dma_map_ops iommu_dma_ops = {
 	.alloc = __iommu_alloc_attrs,
 	.free = __iommu_free_attrs,
@@ -799,7 +817,7 @@ static void __iommu_unmap_sg_attrs(struct device *dev,
 	.sync_sg_for_device = __iommu_sync_sg_for_device,
 	.map_resource = iommu_dma_map_resource,
 	.unmap_resource = iommu_dma_unmap_resource,
-	.dma_supported = iommu_dma_supported,
+	.dma_supported = __iommu_dma_supported,
 	.mapping_error = iommu_dma_mapping_error,
 };
 
-- 
Qualcomm Datacenter Technologies, Inc. on behalf of Qualcomm Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux
Foundation Collaborative Project.