linux-kernel - Re: [PATCH] dw_dmac: apply default dma

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Message-ID: <CAKohpo=upCjze53v5STZJUz5OSrRqBU+mU3Q-C9BL18sXYAs5Q@mail.gmail.com>
Date:	Tue, 29 Jan 2013 20:53:04 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Arnd Bergmann <arnd.bergmann@...aro.org>
Cc:	Vinod Koul <vinod.koul@...el.com>, linux-kernel@...r.kernel.org,
	spear-devel <spear-devel@...t.st.com>
Subject: Re: [PATCH] dw_dmac: apply default dma_mask if needed

Adding Arnd in cc.

On 29 January 2013 20:36, Andy Shevchenko
<andriy.shevchenko@...ux.intel.com> wrote:
> In some cases we got the device without dma_mask configured. We have to apply
> the default value to avoid crashes during memory mapping.
>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> ---
>  drivers/dma/dw_dmac.c |    6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/drivers/dma/dw_dmac.c b/drivers/dma/dw_dmac.c
> index e8d0679..a572a1e 100644
> --- a/drivers/dma/dw_dmac.c
> +++ b/drivers/dma/dw_dmac.c
> @@ -1673,6 +1673,12 @@ static int dw_probe(struct platform_device *pdev)
>         if (IS_ERR(regs))
>                 return PTR_ERR(regs);
>
> +       /* Apply default dma_mask if needed */
> +       if (!pdev->dev.dma_mask) {
> +               pdev->dev.dma_mask = &pdev->dev.coherent_dma_mask;
> +               pdev->dev.coherent_dma_mask = DMA_BIT_MASK(32);
> +       }
> +

Hmm... Why is it required for a DMA controller? What kind of crash do you
get?

@Arnd: Is this change recommended?
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