Re: Question about EMMC CMDQ HOST CONTROLLER INTERFACE (CQHCI) DRIVER

[Adrian Hunter <adrian.hunter@intel.com>]

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".
> 
> 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@vger.kernel.org because others
can answer too.

Regards
Adrian