Re: [PATCH] [v6] net: emac: emac gigabit ethernet controller driver

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On Friday, June 24, 2016 6:46:48 PM CEST Timur Tabi wrote:
> +       /* The EMAC itself is capable of 64-bit DMA. If the SOC limits that
> +        * range, then we expect platform code to adjust the mask accordingly.
> +        */
> +       ret = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(64));
> +       if (ret) {
> +               dev_err(&pdev->dev, "could not set DMA mask\n");
> +               return ret;
> +       }
> 

The comment does not match the code: if the platform has no IOMMU
and the bus limit is smaller than the memory, dma_set_mask_and_coherent()
will fail, and the driver should instead ensure that the buffers are
allocated from the 32-bit area.

Alternatively, adjust the comment to explain that this is a limitation
in the driver that can be lifted if necessary.

	Arnd 
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