Subject: Re: [PATCH v4 1/3] mmc: sdhci: Set DMA mask when adding host
To: Arnd Bergmann <arnd@arndb.de>
References: <1457316477-8153-1-git-send-email-acourbot@nvidia.com>
 <1457316477-8153-2-git-send-email-acourbot@nvidia.com>
 <56E91CB5.7030007@intel.com> <4404643.KcAFCUffYS@wuerfel>
Cc: Alexandre Courbot <acourbot@nvidia.com>,
        Ulf Hansson <ulf.hansson@linaro.org>, linux-mmc@vger.kernel.org,
        linux-kernel@vger.kernel.org, gnurou@gmail.com
From: Adrian Hunter <adrian.hunter@intel.com>
Organization: Intel Finland Oy, Registered Address: PL 281, 00181 Helsinki,
 Business Identity Code: 0357606 - 4, Domiciled in Helsinki
Message-ID: <56E926D8.7020908@intel.com>
Date: Wed, 16 Mar 2016 11:26:48 +0200
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On 16/03/16 11:07, Arnd Bergmann wrote:
> On Wednesday 16 March 2016 10:43:33 Adrian Hunter wrote:
>>> +
>>> +     /* 32-bit mask as default & fallback */
>>> +     if (ret) {
>>> +             ret = dma_set_mask_and_coherent(dev, DMA_BIT_MASK(32));
>>
>> What happens if device enumeration (e.g. of_dma_configure) has already set a
>> more restrictive DMA mask?
>>
>>
> 
> In this case, dma_set_mask_and_coherent() is supposed to check the
> bus properties settings again and fail dma_set_mask_and_coherent().

So the logic this patch introduces will disable DMA in that case.  Would it
be better just to leave the DMA mask alone (as it does now for most sdhci
drivers) in the 32-bit case?