From: Duc Dang <dhd...@apm.com>

The xhci platform driver needs to work on systems that
either only support 64-bit DMA or only support 32-bit DMA.
Attempt to set a coherent dma mask for 64-bit DMA, and
attempt again with 32-bit DMA if that fails.

[dhdang: regenerate the patch over v4.3-rc1 and address new comments]
Signed-off-by: Mark Langsdorf <mlang...@redhat.com>
Tested-by: Mark Salter <msal...@redhat.com>
Signed-off-by: Duc Dang <dhd...@apm.com>
Acked-by: Arnd Bergmann <a...@arndb.de>
Signed-off-by: Mathias Nyman <mathias.ny...@linux.intel.com>
---
 drivers/usb/host/xhci-plat.c | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/drivers/usb/host/xhci-plat.c b/drivers/usb/host/xhci-plat.c
index 890ad9d..34c93e8 100644
--- a/drivers/usb/host/xhci-plat.c
+++ b/drivers/usb/host/xhci-plat.c
@@ -93,14 +93,20 @@ static int xhci_plat_probe(struct platform_device *pdev)
        if (irq < 0)
                return -ENODEV;
 
-       /* Initialize dma_mask and coherent_dma_mask to 32-bits */
-       ret = dma_set_coherent_mask(&pdev->dev, DMA_BIT_MASK(32));
-       if (ret)
-               return ret;
-       if (!pdev->dev.dma_mask)
-               pdev->dev.dma_mask = &pdev->dev.coherent_dma_mask;
+       /* Try to set 64-bit DMA first */
+       if (WARN_ON(!pdev->dev.dma_mask))
+               /* Platform did not initialize dma_mask */
+               ret = dma_coerce_mask_and_coherent(&pdev->dev,
+                                                  DMA_BIT_MASK(64));
        else
-               dma_set_mask(&pdev->dev, DMA_BIT_MASK(32));
+               ret = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(64));
+
+       /* If seting 64-bit DMA mask fails, fall back to 32-bit DMA mask */
+       if (ret) {
+               ret = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(32));
+               if (ret)
+                       return ret;
+       }
 
        hcd = usb_create_hcd(driver, &pdev->dev, dev_name(&pdev->dev));
        if (!hcd)
-- 
1.9.1

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