[PATCH v9 2/4] iommu/dma: Add a helper function to reserve HW MSI address regions for IOMMU drivers

-----Original Message-----
From: Lorenzo Pieralisi [mailto:lorenzo.pieralisi at arm.com]
Sent: Friday, November 03, 2017 11:35 AM
To: Shameerali Kolothum Thodi <redacted>
Cc: Robin Murphy <robin.murphy@arm.com>; Will Deacon
[off-list ref]; Gabriele Paoloni [off-list ref];
marc.zyngier at arm.com; linux-pci at vger.kernel.org; joro at 8bytes.org; John
Garry [off-list ref]; Guohanjun (Hanjun Guo)
[off-list ref]; Linuxarm [off-list ref]; linux-
acpi at vger.kernel.org; iommu at lists.linux-foundation.org; Wangzhou (B)
[off-list ref]; sudeep.holla at arm.com; bhelgaas at google.com;
linux-arm-kernel at lists.infradead.org; devel at acpica.org
Subject: Re: [PATCH v9 2/4] iommu/dma: Add a helper function to reserve HW
MSI address regions for IOMMU drivers

On Thu, Oct 26, 2017 at 10:11:58AM +0000, Shameerali Kolothum Thodi wrote:

[..]

quoted

As we still don?t have a clear resolution on how to invoke the
iort_iommu_msi_get_resv_regions(), I have gone back and attempted to
move the smmu model check inside the iort code. This means the
function will selectively apply HW MSI reservation based on the
platform and also the function can be invoked from the

iommu_dma_get_resv_regions() directly.

quoted

Could you please take a look at the below snippet and let me know your

feedback.

quoted

Hope we can make some progress on this series.

Thanks,
Shameer

-->8--

diff --git a/drivers/acpi/arm64/iort.c b/drivers/acpi/arm64/iort.c
index 876c0e1..a27233d 100644
--- a/drivers/acpi/arm64/iort.c
+++ b/drivers/acpi/arm64/iort.c

@@ -619,6 +619,39 @@ static int __maybe_unused __get_pci_rid(struct

pci_dev *pdev, u16 alias,

quoted

 	return 0;
 }

+static bool __maybe_unused iort_hw_msi_resv_enable(struct device *dev,
+					struct acpi_iort_node *node)
+{
+	struct acpi_iort_node *iommu = NULL;
+	int i;
+
+	if (dev_is_pci(dev)) {
+		u32 rid;
+
+		pci_for_each_dma_alias(to_pci_dev(dev), __get_pci_rid, &rid);
+		iommu = iort_node_map_id(node, rid, NULL,

IORT_IOMMU_TYPE);

quoted

+	} else {
+		for (i = 0; i < node->mapping_count; i++) {
+			iommu = iort_node_map_platform_id(node, NULL,
+							IORT_IOMMU_TYPE,

i);

quoted

+			if (iommu)
+				break;
+		}
+	}

You do not need (and I do not want this code) to do the mapping again.

You have the fwnode (ie dev->iommu_fwspec) corresponding to the IOMMU,
you can retrieve the SMMU IORT node by a simple look-up and carry out the
check below.

Ok. Understood. I will rework this part then.

It would be simpler to set an option in the SMMUv3 driver but then you go back
to square one with DT/ACPI SMMUv3 driver awareness so, if, with the change
above this can make the generic approach work (ie Robin is happy with it) I am
fine with this IORT update as well.

Thanks Lorenzo. I will rebase on top of rc1 and prepare v10 with these changes
and sent it out.

Shameer