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")
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
