[PATCH 1/3] xhci: also avoid the XHCI_ZERO_64B_REGS quirk with a passthrough iommu

[Mathias Nyman <mathias.nyman@linux.intel.com>]

From: D Scott Phillips <scott@os.amperecomputing.com>

Previously the quirk was skipped when no iommu was present. The same
rationale for skipping the quirk also applies in the iommu.passthrough=1
case.

Skip applying the XHCI_ZERO_64B_REGS quirk if the device's iommu domain is
passthrough.

Fixes: 12de0a35c996 ("xhci: Add quirk to zero 64bit registers on Renesas PCIe controllers")
Signed-off-by: D Scott Phillips <scott@os.amperecomputing.com>
Acked-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
---
 drivers/usb/host/xhci.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index 6183ce8574b1..bdb6dd819a3b 100644
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -9,6 +9,7 @@
  */
 
 #include <linux/pci.h>
+#include <linux/iommu.h>
 #include <linux/iopoll.h>
 #include <linux/irq.h>
 #include <linux/log2.h>
@@ -228,6 +229,7 @@ int xhci_reset(struct xhci_hcd *xhci, u64 timeout_us)
 static void xhci_zero_64b_regs(struct xhci_hcd *xhci)
 {
 	struct device *dev = xhci_to_hcd(xhci)->self.sysdev;
+	struct iommu_domain *domain;
 	int err, i;
 	u64 val;
 	u32 intrs;
@@ -246,7 +248,9 @@ static void xhci_zero_64b_regs(struct xhci_hcd *xhci)
 	 * an iommu. Doing anything when there is no iommu is definitely
 	 * unsafe...
 	 */
-	if (!(xhci->quirks & XHCI_ZERO_64B_REGS) || !device_iommu_mapped(dev))
+	domain = iommu_get_domain_for_dev(dev);
+	if (!(xhci->quirks & XHCI_ZERO_64B_REGS) || !domain ||
+	    domain->type == IOMMU_DOMAIN_IDENTITY)
 		return;
 
 	xhci_info(xhci, "Zeroing 64bit base registers, expecting fault\n");
-- 
2.25.1