Limit SD card clock frequency under Linux

Technical Support
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1

We are currently porting our WinEC7 based application to Linux (own distribution). In order to work around some layout weaknesses we have to limit the SD clock speed over the WinEC7 registry to 25MHz (Colibri/Apalis i.MX6 SD card interface). This is the only way to detect SD cards without any problems.

Is it possible to limit the SD clock speed to 25MHz under Linux? How/where can this be done?

PS: This is a follow up ticket of Some SD cards not detected - Technical Support - Toradex Community

2

You can do it by configuring or modifying SDHC driver. Since your are using own distribution it’s hard to say how exactly to do this. Please check esdhc_pltfm_set_clock() of /drivers/mmc/host/sdhci-esdhc-imx.c kernel driver.

3

Thank you for the hint. This will help us to implement a solution.