On Sat, Aug 8, 2015 at 2:22 AM, Russell King - ARM Linux
<linux@xxxxxxxxxxxxxxxx> wrote:
> 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.
>
Hi Russell,
I will add the 2 lines you mentioned back to next version of the
patch. It is safer to do it that way as I do not see
pdev->dev.dma_mask gets initialized before the call
dma_set_mask_and_coherent inside this xhci_plat.c file.
> --
> FTTC broadband for 0.8mile line: currently at 10.5Mbps down 400kbps up
> according to speedtest.net.
--
Regards,
Duc Dang.
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