Messages in this thread | | | Date | Sat, 8 Aug 2015 10:22:52 +0100 | From | Russell King - ARM Linux <> | Subject | Re: [PATCH v5 1/2] usb: make xhci platform driver use 64 bit or 32 bit DMA |
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On Fri, Aug 07, 2015 at 08:18:48PM -0700, Duc Dang wrote: > diff --git a/drivers/usb/host/xhci-plat.c b/drivers/usb/host/xhci-plat.c > index 890ad9d..5d03f8b 100644 > --- a/drivers/usb/host/xhci-plat.c > +++ b/drivers/usb/host/xhci-plat.c > @@ -93,14 +93,14 @@ 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; > - else > - dma_set_mask(&pdev->dev, DMA_BIT_MASK(32)); > + /* Try setting the coherent_dma_mask to 64 bits, then try 32 bits */ > + 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; > + }
Note that dma_set_mask_and_coherent() and the original code are not equivalent because of this:
if (!pdev->dev.dma_mask) pdev->dev.dma_mask = &pdev->dev.coherent_dma_mask;
If we know that pdev->dev.dma_mask will always be initialised at this point, then the above change is fine. If not, it's introducing a regression - dma_set_mask_and_coherent() will fail if pdev->dev.dma_mask is NULL (depending on the architectures implementation of dma_set_mask()).
Prefixing the above change with the two lines I mention above would ensure equivalent behaviour. Even if we do want to get rid of this, I'd advise to do it as a separate patch after this change, which can be independently reverted if there's problems with its removal.
-- FTTC broadband for 0.8mile line: currently at 10.5Mbps down 400kbps up according to speedtest.net.
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