-----Original Message-----
From: Will Deacon [mailto:will.deacon at arm.com]
Sent: Friday, July 14, 2017 8:33 PM
To: Shameerali Kolothum Thodi
Cc: lorenzo.pieralisi at arm.com; marc.zyngier at arm.com;
sudeep.holla at arm.com; robin.murphy at arm.com; hanjun.guo at linaro.org;
Gabriele Paoloni; John Garry; Linuxarm; linux-acpi at vger.kernel.org;
iommu at lists.linux-foundation.org; Wangzhou (B); Guohanjun (Hanjun Guo);
linux-arm-kernel at lists.infradead.org; devel at acpica.org
Subject: Re: [PATCH v3 2/2] iommu/arm-smmu-v3:Enable ACPI based
HiSilicon erratum 161010801

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-	list_add_tail(&region->list, head);
+	if ((smmu->options & ARM_SMMU_OPT_RESV_HW_MSI)) {
+
+		if (!is_of_node(smmu->dev->fwnode))
+			resv = iort_iommu_its_get_resv_regions(dev, head);

How does this work when we're not using ACPI? Shouldn't of vs ACPI
be abstracted from the driver?

At present ARM_SMMU_OPT_RESV_HW_MSI is only set for ACPI and  DT
support for this is a low priority for us at the moment. Is the
suggestion is to have a common function outside the smmu driver for
_iommu_its_get_resv_regions() ? I am not sure what is the best way here.

Right, something like that. The driver shouldn't need to care whether or not
it's using ACPI or DT when setting these options.

Below is what I have in mind for the common function for msi reserve.
But just wondering invoking iort_ functions from iommu code 
is acceptable or not . Could you please take a look and let me know.

Many thanks,
Shameer

--- 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);