diff mbox series

usb: host: xhci-tegra: Set DMA mask correctly

Message ID 1566989697-13049-1-git-send-email-nkristam@nvidia.com (mailing list archive)
State Mainlined
Commit 993cc8753453fccfe060a535bbe21fcf1001b626
Headers show
Series usb: host: xhci-tegra: Set DMA mask correctly | expand

Commit Message

Nagarjuna Kristam Aug. 28, 2019, 10:54 a.m. UTC 
The Falcon microcontroller that runs the XUSB firmware and which is
responsible for exposing the XHCI interface can address only 40 bits of
memory. Typically that's not a problem because Tegra devices don't have
enough system memory to exceed those 40 bits.

However, if the ARM SMMU is enable on Tegra186 and later, the addresses
passed to the XUSB controller can be anywhere in the 48-bit IOV address
space of the ARM SMMU. Since the DMA/IOMMU API starts allocating from
the top of the IOVA space, the Falcon microcontroller is not able to
load the firmware successfully.

Fix this by setting the DMA mask to 40 bits, which will force the DMA
API to map the buffer for the firmware to an IOVA that is addressable by
the Falcon.

Signed-off-by: Nagarjuna Kristam <nkristam@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
---
 drivers/usb/host/xhci-tegra.c | 10 ++++++++++
 1 file changed, 10 insertions(+)
diff mbox series

Patch

diff --git a/drivers/usb/host/xhci-tegra.c b/drivers/usb/host/xhci-tegra.c
index dafc659..2ff7c91 100644
--- a/drivers/usb/host/xhci-tegra.c
+++ b/drivers/usb/host/xhci-tegra.c
@@ -1194,6 +1194,16 @@  static int tegra_xusb_probe(struct platform_device *pdev)
 
 	tegra_xusb_config(tegra, regs);
 
+	/*
+	 * The XUSB Falcon microcontroller can only address 40 bits, so set
+	 * the DMA mask accordingly.
+	 */
+	err = dma_set_mask_and_coherent(tegra->dev, DMA_BIT_MASK(40));
+	if (err < 0) {
+		dev_err(&pdev->dev, "failed to set DMA mask: %d\n", err);
+		goto put_rpm;
+	}
+
 	err = tegra_xusb_load_firmware(tegra);
 	if (err < 0) {
 		dev_err(&pdev->dev, "failed to load firmware: %d\n", err);