linux-kernel - Re: [PATCH v3 1/3] mmc: sdhci: Set DMA mask when adding host

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Date:	Mon, 7 Mar 2016 11:06:06 +0900
From:	Alexandre Courbot <gnurou@...il.com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Alexandre Courbot <acourbot@...dia.com>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Adrian Hunter <adrian.hunter@...el.com>,
	linux-mmc <linux-mmc@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 1/3] mmc: sdhci: Set DMA mask when adding host

On Sat, Mar 5, 2016 at 12:57 AM, Arnd Bergmann <arnd@...db.de> wrote:
> On Friday 04 March 2016 19:38:43 Alexandre Courbot wrote:
>> Set the DMA mask in sdhci_add_host() after we determined the
>> capabilities of the device. 64-bit devices in particular are given the
>> proper mask that ensures bounce buffers are not used.
>>
>> Also disable DMA if no proper DMA mask can be set, as the DMA-API
>> documentation specifies.
>>
>> Signed-off-by: Alexandre Courbot <acourbot@...dia.com>
>> ---
>>  drivers/mmc/host/sdhci.c | 46 +++++++++++++++++++++++++++++++++++++++-------
>>  1 file changed, 39 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
>> index fd9139947fa3..00fb45ba6f39 100644
>> --- a/drivers/mmc/host/sdhci.c
>> +++ b/drivers/mmc/host/sdhci.c
>> @@ -2857,6 +2857,34 @@ struct sdhci_host *sdhci_alloc_host(struct device *dev,
>>
>>  EXPORT_SYMBOL_GPL(sdhci_alloc_host);
>>
>> +static int sdhci_set_dma_mask(struct sdhci_host *host)
>> +{
>> +     struct mmc_host *mmc = host->mmc;
>> +     struct device *dev = mmc_dev(mmc);
>> +     int ret = -EINVAL;
>> +
>> +     if (host->quirks2 & SDHCI_QUIRK2_BROKEN_64_BIT_DMA)
>> +             host->flags &= ~SDHCI_USE_64_BIT_DMA;
>> +
>> +     /* Try 64-bit mask if hardware is capable  of it */
>> +     if (host->flags & SDHCI_USE_64_BIT_DMA) {
>> +             ret = dma_set_mask_and_coherent(dev, DMA_BIT_MASK(64));
>> +             if (ret)
>> +                     pr_warn("%s: Failed to set 64-bit DMA mask.\n",
>> +                             mmc_hostname(mmc));
>> +     }
>> +
>
> I think you need to disable the SDHCI_USE_64_BIT_DMA flag when
> dma_set_mask_and_coherent() fails here. Otherwise looks good.

Ah, you're right, thanks. v4 is on the way.