sdhci timeout on imx8mq

[Fabio Estevam]

Hi Lucas,

On Tue, Jan 5, 2021 at 12:06 PM Lucas Stach <l.stach at pengutronix.de> wrote:

> The reference manual states about this situation: "For any clock, its
> source must be left on when it is kept on. Behavior is undefined if
> this rule is violated."
> And it seems this is exactly what's happening here: some kind of glitch
> is introduced in the nand_usdhc_bus clock, which prevents the SDHCI
> controller from working, even though the clock branch is properly
> enabled later on. On my system the SDHCI timeout and following runtime
> suspend/resume cycle on the nand_usdhc_bus clock seem to get it back
> into a working state.

I think your analysis is correct and I recall helping a customer with
a similar issue:
https://community.nxp.com/t5/i-MX-Processors/External-clock-that-provide-root-clock-for-SAI3-and-SPDIF/m-p/1019834

Regards,

Fabio Estevam