[PATCH v6 2/3] iommu/dma: Add a helper function to reserve HW MSI address regions for IOMMU drivers

[Shameer Kolothum]

IOMMU drivers can use this to implement their .get_resv_regions callback
for HW MSI specific reservations(e.g. ARM GICv3 ITS MSI region).

Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi at huawei.com>
---
 drivers/iommu/dma-iommu.c | 19 +++++++++++++++++++
 include/linux/dma-iommu.h |  7 +++++++
 2 files changed, 26 insertions(+)

diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index 9d1cebe..952ecdd 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -19,6 +19,7 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+#include <linux/acpi_iort.h>
 #include <linux/device.h>
 #include <linux/dma-iommu.h>
 #include <linux/gfp.h>
@@ -198,6 +199,24 @@ void iommu_dma_get_resv_regions(struct device *dev, struct list_head *list)
 }
 EXPORT_SYMBOL(iommu_dma_get_resv_regions);
 
+/**
+ * iommu_dma_get_msi_resv_regions - Reserved region driver helper
+ * @dev: Device from iommu_get_resv_regions()
+ * @list: Reserved region list from iommu_get_resv_regions()
+ *
+ * IOMMU drivers can use this to implement their .get_resv_regions
+ * callback for HW MSI specific reservations. For now, this only
+ * covers ITS MSI region reservation using ACPI IORT helper function.
+ */
+int iommu_dma_get_msi_resv_regions(struct device *dev, struct list_head *list)
+{
+	if (!is_of_node(dev->iommu_fwspec->iommu_fwnode))
+		return iort_iommu_its_get_resv_regions(dev, list);
+
+	return -ENODEV;
+}
+EXPORT_SYMBOL(iommu_dma_get_msi_resv_regions);
+
 static int cookie_init_hw_msi_region(struct iommu_dma_cookie *cookie,
 		phys_addr_t start, phys_addr_t end)
 {
diff --git a/include/linux/dma-iommu.h b/include/linux/dma-iommu.h
index 92f2083..6062ef0 100644
--- a/include/linux/dma-iommu.h
+++ b/include/linux/dma-iommu.h
@@ -74,6 +74,8 @@ void iommu_dma_unmap_resource(struct device *dev, dma_addr_t handle,
 void iommu_dma_map_msi_msg(int irq, struct msi_msg *msg);
 void iommu_dma_get_resv_regions(struct device *dev, struct list_head *list);
 
+int iommu_dma_get_msi_resv_regions(struct device *dev, struct list_head *list);
+
 #else
 
 struct iommu_domain;
@@ -107,6 +109,11 @@ static inline void iommu_dma_get_resv_regions(struct device *dev, struct list_he
 {
 }
 
+static inline int iommu_dma_get_msi_resv_regions(struct device *dev, struct list_head *list)
+{
+	return -ENODEV;
+}
+
 #endif	/* CONFIG_IOMMU_DMA */
 #endif	/* __KERNEL__ */
 #endif	/* __DMA_IOMMU_H */
-- 
1.9.1