linux-kernel - Re: [PATCH v3 1/2] usb:dwc3: Enable support for 64-bit system

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Date:	Wed, 30 Mar 2016 16:09:21 +0300
From:	Felipe Balbi <felipe.balbi@...ux.intel.com>
To:	"Thang Q. Nguyen" <tqnguyen@....com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-usb@...r.kernel.org, linux-omap@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arm@...ts.infradead.org
Cc:	Thang Nguyen <tqnguyen@....com>, Phong Vo <pvo@....com>,
	Loc Ho <lho@....com>, patches@....com
Subject: Re: [PATCH v3 1/2] usb:dwc3: Enable support for 64-bit system


Hi,

"Thang Q. Nguyen" <tqnguyen@....com> writes:
> From: "Thang Q. Nguyen" <tqnguyen@....com>
>
> Add 64-bit DMA operation support to the USB DWC3 driver.
> First attempt to set the coherent DMA mask for 64-bit DMA.
> If that failed, attempt again with 32-bit DMA.
>
> Changes from v2:
> 	- None.
>
> Changes from v1:
> 	- Remove WARN_ON if dma_mask is NULL

these changes lines should be between the tearline (---) and diffstat
below.

> Signed-off-by: Thang Q. Nguyen <tqnguyen@....com>
> ---
>  drivers/usb/dwc3/core.c | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
>
> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> index de5e01f..2479c24 100644
> --- a/drivers/usb/dwc3/core.c
> +++ b/drivers/usb/dwc3/core.c
> @@ -831,6 +831,21 @@ static int dwc3_probe(struct platform_device *pdev)
>  	dwc->mem = mem;
>  	dwc->dev = dev;
>  
> +	/* Try to set 64-bit DMA first */
> +	if (!pdev->dev.dma_mask)
> +		/* Platform did not initialize dma_mask */
> +		ret = dma_coerce_mask_and_coherent(&pdev->dev,
> +						   DMA_BIT_MASK(64));
> +	else
> +		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;
> +	}

Also, why is it so that you need this now ? glue layers are copying dma
mask from parent device and that should be set properly. This really
shouldn't be necessary in dwc3-core; it would mean that glue layer
didn't set this device up properly.

-- 
balbi

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