[PATCH] dma-mapping: skip USB devices when configuring DMA during probe

From: Johan Hovold
Date: Thu Aug 03 2017 - 06:07:14 EST

USB devices use the DMA mask and offset of the controller, which have
already been setup when a device is probed. Note that modifying the mask
of a USB device would change the mask for the controller (and all
devices on the bus) as the mask is literally shared.

Since commit 2bf698671205 ("USB: of: fix root-hub device-tree node
handling"), of_dma_configure() would be called also for root hubs, which
use the device node of the controller. A separate bug that makes
of_dma_configure() generate a 30-bit DMA mask from the RPI3's
"dma-ranges" would thus set a broken mask also for the controller. This
in turn leads to USB devices failing to enumerate when control transfers

dwc2 3f980000.usb: Cannot do DMA to address 0x000000003a166a00

Fix this, and similar future problems, by simply skipping USB devices
when dma_configure() is called during probe.

Fixes: 09515ef5ddad ("of/acpi: Configure dma operations at probe time for platform/amba/pci bus devices")
Cc: stable <stable@xxxxxxxxxxxxxxx> # 4.12
Cc: Robin Murphy <robin.murphy@xxxxxxx>
Cc: Sricharan R <sricharan@xxxxxxxxxxxxxx>
Cc: Stefan Wahren <stefan.wahren@xxxxxxxx>
Reported-by: Hans Verkuil <hverkuil@xxxxxxxxx>
Signed-off-by: Johan Hovold <johan@xxxxxxxxxx>
drivers/base/dma-mapping.c | 8 ++++++++
1 file changed, 8 insertions(+)

diff --git a/drivers/base/dma-mapping.c b/drivers/base/dma-mapping.c
index b555ff9dd8fc..c6cde7e79599 100644
--- a/drivers/base/dma-mapping.c
+++ b/drivers/base/dma-mapping.c
@@ -13,6 +13,7 @@
#include <linux/gfp.h>
#include <linux/of_device.h>
#include <linux/slab.h>
+#include <linux/usb.h>
#include <linux/vmalloc.h>

@@ -345,6 +346,10 @@ int dma_configure(struct device *dev)
enum dev_dma_attr attr;
int ret = 0;

+ /* USB devices share the controller's mask. */
+ if (dev->bus == &usb_bus_type)
+ return 0;
if (dev_is_pci(dev)) {
bridge = pci_get_host_bridge_device(to_pci_dev(dev));
dma_dev = bridge;
@@ -369,6 +374,9 @@ int dma_configure(struct device *dev)

void dma_deconfigure(struct device *dev)
+ if (dev->bus == &usb_bus_type)
+ return;