imx6 solo sd-card UHS-I question (linux 3.10.17)

[philipperey]

Hello everyone,

We want to support UHS-I mode on our board for our sd-card (sd3 port of imx). Hardware wise, we kind of copied the sabre sd automative schematics,but we didn't wired the sd3 RST signal to a power regulator to switch off and on the sd-card power (that is, the power of the sd-card is always switched on).

In the imx6qdl-sabreauto.dtsi, at the usdhc3 declaration there is a paragraph stating that power off is needed for SD3.0 card re-enumeration in UHS mode.

Hence, my question is, is it absolutely mandatory to have a vmmc-regulator with power off / on declared on SD3_RST pin declared to support UHS mode at run time ? (not at boot).

Thank you guys,

ps : I'm using a 3.10.17 freescale linux kernel.

Phil

[igorpadykov · Accepted solution]

Hi Phil

according to sd specs seems this is needed:

https://www.sdcard.org/downloads/pls/pdf/part1_410.pdf

p.150  sect.6.4.1.5 Power Down and Power Cycle

If the host needs to change the operating voltage, a power cycle is required.

Best regards
igor
-----------------------------------------------------------------------------------------------------------------------
Note: If this post answers your question, please click the Correct Answer button. Thank you!
-----------------------------------------------------------------------------------------------------------------------

[philipperey]

Thanks Igor, looking at the document you linked it seems power cycle is required as you said. We will modify the hardware to support that.

Phil