On Fri, Jul 15, 2016 at 02:34:02PM +0530, Anup Patel wrote:
> +static int uio_dmem_genirq_alloc_platdata(struct platform_device *pdev)
> +{
> + struct uio_dmem_genirq_pdata pdata;
> + u32 dma_bits, regions;
> + u32 sizes[MAX_UIO_MAPS];
> + int ret;
> +
> + memset(&pdata, 0, sizeof(pdata));
> +
> + ret = of_property_read_u32(pdev->dev.of_node,
> + uio_of_dma_bits_prop, &dma_bits);
> + if (ret) {
> + dev_err(&pdev->dev,
> + "Missing property %s\n", uio_of_dma_bits_prop);
> + return ret;
> + }
> + if (dma_bits > 64)
> + dma_bits = 64;
> +
> + dma_set_coherent_mask(&pdev->dev, DMA_BIT_MASK(dma_bits));
You really need to check the return value from this: this function
negotiates with the architecture, and if 64-bit DMA is not supported,
then the call will fail and you as a driver are expected to fall back
to 32-bit DMA only.
In that case, you're expected to call the same function with a 32-bit
mask, and if that fails, you're supposed to then decide that DMA is
not possible.
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