Re: [PATCH 00/15] mmc: sdhci: Add 64-bit ADMA support

Adrian Hunter
2014-10-30T10:52:29Z

On 30/10/14 12:00, Arnd Bergmann wrote:
> On Thursday 30 October 2014 10:40:12 Adrian Hunter wrote:
>> On 30/10/14 10:05, Arnd Bergmann wrote:
>>> On Thursday 30 October 2014 09:25:54 Adrian Hunter wrote:
>>>> On 21/10/14 12:26, Adrian Hunter wrote:
>>>>> Hi
>>>>>
>>>>> Here are patches to add 64-bit ADMA support to the SDHCI driver.
>>>>>
>>>>> The patchset starts with 3 minor fixes related to SDHCI ADMA,
>>>>> then there are 8 preparatory patches, then 3 main patches, then
>>>>> the mmc_test "Badly aligned" tests are extended slightly.
>>>>
>>>> Hi Ulf
>>>>
>>>> Can you take these? Note that there was a V2 of
>>>> "mmc: sdhci-acpi: Add 64-bit DMA support". Also
>>>> that patch is dependent (for functionality not
>>>> compilation) on a patch in v3.18-rc2 so it is slightly
>>>> preferable if you pull v3.18-rc2 first.
>>>
>>> You still haven't addressed my comments about clearing
>>> the SDHCI_USE_64_BIT_DMA flag if the platform finds that
>>> hardware has set this bit incorrectly.
>>
>> Yes I did. I said there was no need:
>>
>> http://marc.info/?l=linux-mmc&m=141449082331402&w=2
>>
>> I would also note that the SDHCI spec does not say explicitly
>> that a 64-bit device supports 32-bit DMA descriptors.
>>
>> If the hardware really is broken, the SDHCI_QUIRK2_BROKEN_64_BIT_DMA
>> should be used.
>
> You also said that the flag is defined to mean that 64-bit DMA
> is working and that you want to show the warning when the hardware
> and the firmware disagree about this. If you have an (at least)
> 50% chance that the hardware is lying, you really shouldn't believe
> it.

Just because there are two options does not mean they are each equally
likely.