From mboxrd@z Thu Jan  1 00:00:00 1970
From: Arnd Bergmann <arnd@arndb.de>
Subject: Re: [PATCH V2] mmc: sdhci-acpi: Add 64-bit DMA support
Date: Tue, 28 Oct 2014 10:43:14 +0100
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References: <26081691.uIqsxnCCe6@wuerfel> <1414485440-29673-1-git-send-email-adrian.hunter@intel.com>
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To: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ulf Hansson <ulf.hansson@linaro.org>, Chris Ball <chris@printf.net>, linux-mmc <linux-mmc@vger.kernel.org>

On Tuesday 28 October 2014 10:37:20 Adrian Hunter wrote:
>  static int sdhci_acpi_enable_dma(struct sdhci_host *host)
>  {
> -       return 0;
> +       struct sdhci_acpi_host *c = sdhci_priv(host);
> +       struct device *dev = &c->pdev->dev;
> +       int err = -1;
> +
> +       if (c->dma_setup)
> +               return 0;
> +
> +       if (host->flags & SDHCI_USE_64_BIT_DMA) {
> +               if (host->quirks2 & SDHCI_QUIRK2_BROKEN_64_BIT_DMA) {
> +                       host->flags &= ~SDHCI_USE_64_BIT_DMA;
> +               } else {
> +                       err = dma_set_mask_and_coherent(dev, DMA_BIT_MASK(64));
> +                       if (err)
> +                               dev_warn(dev, "Failed to set 64-bit DMA mask\n");
> +               }
> +       }
> +
> +       if (err)
> +               err = dma_set_mask_and_coherent(dev, DMA_BIT_MASK(32));
> +
> +       c->dma_setup = !err;
> +
> +       return err;
>  }
> 

I don't think it's worth a dev_warn() message (maybe dev_info), there is nothing
wrong in this case, but you probably have to clear the SDHCI_USE_64_BIT_DMA to
ensure that the driver won't try to to use the 64-bit DMA if the mask is not set.

	Arnd