linux-kernel - Re: [PATCH v7 1/2] usb: make xhci platform driver use 64 bit or 32 bit DMA

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Date:	Mon, 31 Aug 2015 11:58:48 -0700
From:	Duc Dang <dhdang@....com>
To:	Greg KH <gregkh@...uxfoundation.org>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Loc Ho <lho@....com>, Arnd Bergmann <arnd@...db.de>
Cc:	USB list <linux-usb@...r.kernel.org>,
	linux-arm <linux-arm-kernel@...ts.infradead.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	mathias.nyman@...el.com, Mark Langsdorf <mlangsdo@...hat.com>,
	patches <patches@....com>, Feng Kan <fkan@....com>,
	Duc Dang <dhdang@....com>
Subject: Re: [PATCH v7 1/2] usb: make xhci platform driver use 64 bit or 32
 bit DMA

On Thu, Aug 20, 2015 at 12:38 PM, Duc Dang <dhdang@....com> wrote:
> 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@...hat.com>
> Tested-by: Mark Salter <msalter@...hat.com>
> Signed-off-by: Duc Dang <dhdang@....com>
>
> ---
> Changes from v6:
>         -Add WARN_ON if dma_mask is NULL
>         -Use dma_coerce_mask_and_coherent to assign
>         dma_mask and coherent_dma_mask
>
> 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:
>         -None
>
> Changes from v3:
>         -Re-generate the patch over 4.2-rc5
>         -No code change.
>
> Changes from v2:
>         -None
>
> 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 | 21 +++++++++++++--------
>  1 file changed, 13 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/usb/host/xhci-plat.c b/drivers/usb/host/xhci-plat.c
> index 890ad9d..e4c7f9d 100644
> --- a/drivers/usb/host/xhci-plat.c
> +++ b/drivers/usb/host/xhci-plat.c
> @@ -93,14 +93,19 @@ 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));
> +       /* Throw a waring if broken platform code didn't initialize dma_mask */
> +       WARN_ON(!pdev->dev.dma_mask);
> +       /*
> +        * Try setting dma_mask and coherent_dma_mask to 64 bits,
> +        * then try 32 bits
> +        */
> +       ret = dma_coerce_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(64));
> +       if (ret) {
> +               ret = dma_coerce_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
>

Hi Greg, Arnd, Russell,

Do you have any more comment about this patch set?

-- 
Duc Dang.
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