[PATCH v1 4/6] pci/arm: Use iommu_add_dt_pci_device() instead of arch hook

[Stewart Hildebrand <stewart.hildebrand@xxxxxxx>]

From: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>

On Arm we need to parse DT PCI-IOMMU specifier and provide it to
the driver (for describing the relationship between PCI devices
and IOMMUs) before adding a device to it.

Also clarify the check of the return value as iommu_add_pci_device
can return >0 if a device doesn't need to be protected by the IOMMU
and print a warning if iommu_add_pci_device failed.

Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
Signed-off-by: Stewart Hildebrand <stewart.hildebrand@xxxxxxx>
---
downstream->v1:
* rebase
* add __maybe_unused attribute to const struct domain_iommu *hd;
* Rename: s/iommu_add_pci_device/iommu_add_dt_pci_device/
* guard iommu_add_dt_pci_device call with CONFIG_HAS_DEVICE_TREE instead of
  CONFIG_ARM

(cherry picked from commit 2b9d26badab8b24b5a80d028c4499a5022817213 from
 the downstream branch poc/pci-passthrough from
 https://gitlab.com/xen-project/people/bmarquis/xen-arm-poc.git)
---
 xen/drivers/passthrough/pci.c | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/xen/drivers/passthrough/pci.c b/xen/drivers/passthrough/pci.c
index b42acb8d7c09..ed5a6ede7847 100644
--- a/xen/drivers/passthrough/pci.c
+++ b/xen/drivers/passthrough/pci.c
@@ -1305,7 +1305,7 @@ __initcall(setup_dump_pcidevs);
 
 static int iommu_add_device(struct pci_dev *pdev)
 {
-    const struct domain_iommu *hd;
+    const struct domain_iommu *hd __maybe_unused;
     int rc;
     unsigned int devfn = pdev->devfn;
 
@@ -1318,17 +1318,30 @@ static int iommu_add_device(struct pci_dev *pdev)
     if ( !is_iommu_enabled(pdev->domain) )
         return 0;
 
+#ifdef CONFIG_HAS_DEVICE_TREE
+    rc = iommu_add_dt_pci_device(devfn, pdev);
+#else
     rc = iommu_call(hd->platform_ops, add_device, devfn, pci_to_dev(pdev));
-    if ( rc || !pdev->phantom_stride )
+#endif
+    if ( rc < 0 || !pdev->phantom_stride )
+    {
+        if ( rc < 0 )
+            printk(XENLOG_WARNING "IOMMU: add %pp failed (%d)\n",
+                   &pdev->sbdf, rc);
         return rc;
+    }
 
     for ( ; ; )
     {
         devfn += pdev->phantom_stride;
         if ( PCI_SLOT(devfn) != PCI_SLOT(pdev->devfn) )
             return 0;
+#ifdef CONFIG_HAS_DEVICE_TREE
+        rc = iommu_add_dt_pci_device(devfn, pdev);
+#else
         rc = iommu_call(hd->platform_ops, add_device, devfn, pci_to_dev(pdev));
-        if ( rc )
+#endif
+        if ( rc < 0 )
             printk(XENLOG_WARNING "IOMMU: add %pp failed (%d)\n",
                    &PCI_SBDF(pdev->seg, pdev->bus, devfn), rc);
     }
-- 
2.40.1