[PATCH v6 1/2] usb: make xhci platform driver use 64 bit or 32 bit DMA

From: Duc Dang
Date: Mon Aug 10 2015 - 03:37:55 EST

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 4.2-rc5 and address new comments]
Signed-off-by: Mark Langsdorf <mlangsdo@xxxxxxxxxx>
Tested-by: Mark Salter <msalter@xxxxxxxxxx>
Signed-off-by: Duc Dang <dhdang@xxxxxxx>

Changes from v5:
-Change comment
-Assign dma_mask to coherent_dma_mask if dma_mask is NULL
to make sure dma_set_mask_and_coherent does not fail prematurely.

Changes from v4:

Changes from v3:
-Re-generate the patch over 4.2-rc5
-No code change.

Changes from v2:

Changes from v1:
-Consolidated to use dma_set_mask_and_coherent
-Got rid of the check against sizeof(dma_addr_t)

drivers/usb/host/xhci-plat.c | 16 ++++++++++------
1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/drivers/usb/host/xhci-plat.c b/drivers/usb/host/xhci-plat.c
index 890ad9d..5d1b84b 100644
--- a/drivers/usb/host/xhci-plat.c
+++ b/drivers/usb/host/xhci-plat.c
@@ -93,14 +93,18 @@ 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;
+ /*
+ * Try setting dma_mask and coherent_dma_mask to 64 bits,
+ * then try 32 bits
+ */
if (!pdev->dev.dma_mask)
pdev->dev.dma_mask = &pdev->dev.coherent_dma_mask;
- else
- dma_set_mask(&pdev->dev, DMA_BIT_MASK(32));
+ ret = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(64));
+ 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)

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