+From 77765c2a47ce43911b8fe7b09f037c9bc13008ca Mon Sep 17 00:00:00 2001
+From: Jeff Kubascik <jeff.kubascik@dornerworks.com>
+Date: Tue, 30 Jul 2019 08:49:56 -0400
+Subject: [PATCH 3/4] Fix PCIe in dom0 for RPi4
+
+There is an issue where the Broadcom PCIe driver and Xen swiotlb layer
+invoke each other's dma alloc function recursively until the stack blows
+up. The cause appears to be due to arch_setup_dma_ops being called
+more than once for the device, possibly through of_dma_configure, and
+screwing up the dma_ops pointers. This patch adds a check to make sure
+that the xen_dma_ops are applied only once for a device.
+---
+ arch/arm64/mm/dma-mapping.c | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c
+index d3a5bb16f..243a3b9be 100644
+--- a/arch/arm64/mm/dma-mapping.c
++++ b/arch/arm64/mm/dma-mapping.c
+@@ -895,7 +895,7 @@ void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,
+ __iommu_setup_dma_ops(dev, dma_base, size, iommu);
+
+ #ifdef CONFIG_XEN
+- if (xen_initial_domain()) {
++ if (!dev->archdata.dev_dma_ops && xen_initial_domain()) {
+ dev->archdata.dev_dma_ops = dev->dma_ops;
+ dev->dma_ops = xen_dma_ops;
+ }
+--
+2.17.1
+