On 8/11/22 10:28, Shawn Lin wrote:
> On 2022/11/8 16:20, Adrian Hunter wrote:
>> On 8/11/22 09:25, Jyan Chou [周芷安] wrote:
>>> Hello Adrian Hunter,
>>>
>>> We are now using the upstream code of EMMC CMDQ HOST CONTROLLER INTERFACE (CQHCI) DRIVER, but we found that the existing driver cannot support the limitation of Synopsys IP.
>>>
>>> Synopsys IP has a description on their data book " While using DMA, the host memory data buffer size and start address must not exceed 128 MB".
>
> Synopsys-based SDHCI IP does have a limitation of 128MB boundary. But it
> has already been solved by upstream driver.
>
> FYI:
>
> commit b85c997d2cfefe7d1f706b85ae46e35a50e3131c ("mmc: sdhci-of-dwcmshc: solve 128MB DMA boundary limitation")
CQHCI has its own DMA descriptors, so maybe a similar change is needed for CQHCI?
>
>>>
>>> I am wondering whether there is a method or patch that can fix this boundary limitation.
>>> Thanks.
>>> Best Regards,
>>> Jyan Chou
>>
>> Hello Jyan Chou
>>
>> I am not clear on what the exact limitation is. The driver never uses buffers as big as 128 MB.
>> To restrict DMA to low memory addresses a DMA mask can be used.
>>
>> But perhaps you mean not to cross a 128 MB boundary?
>>
>> Please cc your questions to the linux kernel mmc mailing list: linux-mmc@xxxxxxxxxxxxxxx because others
>> can answer too.
>>
>> Regards
>> Adrian
