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SubjectRe: [PATCH 30/51] DMA-API: dma: dw_dmac.c: convert to use dma_coerce_mask_and_coherent()
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On Thu, 2013-09-19 at 22:55 +0100, Russell King wrote:
> This code sequence:
> if (!pdev->dev.dma_mask) {
> pdev->dev.dma_mask = &pdev->dev.coherent_dma_mask;
> pdev->dev.coherent_dma_mask = DMA_BIT_MASK(32);
> }
> bypasses the architectures check on the DMA mask. It can be replaced
> with dma_coerce_mask_and_coherent(), avoiding the direct initialization
> of this mask.
>
> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
> ---
> drivers/dma/dw/platform.c | 8 +++-----
> 1 files changed, 3 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/dma/dw/platform.c b/drivers/dma/dw/platform.c
> index e35d975..453822c 100644
> --- a/drivers/dma/dw/platform.c
> +++ b/drivers/dma/dw/platform.c
> @@ -191,11 +191,9 @@ static int dw_probe(struct platform_device *pdev)
> if (IS_ERR(chip->regs))
> return PTR_ERR(chip->regs);
>
> - /* Apply default dma_mask if needed */
> - if (!dev->dma_mask) {
> - dev->dma_mask = &dev->coherent_dma_mask;
> - dev->coherent_dma_mask = DMA_BIT_MASK(32);
> - }
> + err = dma_coerce_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(32));
> + if (err)
> + return err;

I have at least one question.

In case of new code you always assign dev->dma_mask.

static inline int dma_coerce_mask_and_coherent(struct device *dev, u64
mask)
{
dev->dma_mask = &dev->coherent_dma_mask;
return dma_set_mask_and_coherent(dev, mask);
}

So, the question is how keep the initialized dma_mask (and should we do
so by your opinion)?

Additional question, who will free memory allocated for dma_mask in case
if it was allocated, dma_mask initialized and then your code just
substitute the address to some new value?


--
Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Intel Finland Oy


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