SDIO Tuning issue running latest Kernel in Buildroot

[josh25219]

Hi,
We use SDIO to communicate with our wifi card. We used to use buildroot release 2021.11 which used kernel version 5.12.1. When we upgraded to release 2022.05, we have a SDIO Tuning issue.
All codes are based on:
https://github.com/polarfire-soc/polarfire-soc-buildroot-sdk
https://github.com/linux4microchip/linux/blob/29c2077400e2614da14e8e5b31f7bec041f3f4be/drivers/mmc/host/sdhci-cadence.c

The new kernel casued SDIO tuning failure. The reason is that the driver drivers/mmc/host/sdhci-cadence.c added .platform_execute_tuning = sdhci_cdns_execute_tuning, When sdhci_execute_tuning is called, it will use callback function and call sdhci_cdns_execute_tuning and get -EIO error with ""no tuning point found". Removing .platform_execute_tuning = sdhci_cdns_execute_tuning seems to fix the issue.

Is this expected?

Thanks,
Josh

[hughbreslin]

Hi @josh25219

Can I check that when you remove .platform_execute_tuning = sdhci_cdns_execute_tuning your card comes up and works as expected? If so this is expected.

[josh25219]

Hi Hugh,

Yes, removing that line, then things work as expected. I just wanted to make sure that was an expected issue and appropriate work-around. Is tuning not required?

Thanks
Josh

[hughbreslin]

Cool 🙂

The tuning thats running there is software tuning as far as I know, which isn't required by your set up as that tuning should be done by the hardware.