Additional eMMC on custom Verdin carrier board

Technical Support
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#1

Hello,
we need an (additonal) eMMC on our Verdin carrier board. As eMMC is like uSD we take that approach with some changes:

  • We have fixed 1.8V I/O voltage whereas uSD switches between 3.3V and 1.8V.

  • We do not want to switch eMMC power, instead we have a Reset pin. Verdin pin planner has an optional SD_1_RESET# pin (which seems to be a standard digital I/O).

My question is: Is there a eMMC driver available which halts the voltage at 1.8V and uses the Reset function instead of power cycling?
With such a driver we get a very smart HW solution.

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#2

Hello rosenheim,

so we are checking what to do the enable the reset.
The voltage side of this interface is always 1.8 volts. only the main SD card interface has the 3.3 ?1.8 voltage switching so you should be fine on the signal level side.

Best Regards,

Matthias

#3

Hi @rosenheim!

Looking for reset for eMMC, we found the mmc-pwrseq property in the documentation of mmc-controller: mmc-controller.yaml « mmc « bindings « devicetree « Documentation - linux-toradex.git - Linux kernel for Apalis, Colibri and Verdin modules.

This property can point to an mmc-pwrseq-emmc node: mmc-pwrseq-emmc.txt « mmc « bindings « devicetree « Documentation - linux-toradex.git - Linux kernel for Apalis, Colibri and Verdin modules.

Here is a device tree file from the kernel that uses it: rk3368-r88.dts « rockchip « dts « boot « arm64 « arch - linux-toradex.git - Linux kernel for Apalis, Colibri and Verdin modules. You can use it as an inspiration.

I have never used it, so I am not sure if it should be used or if it works. It seems like it is easy to test.

Best regards,