[PATCH 0/2] mmc: sdhci: potentially bad behavior when using vmmc supply

Ulf Hansson ulf.hansson at linaro.org
Mon Nov 9 01:38:03 PST 2015


>> > Is the regulator-gpio usage the right thing to do for vqmmc? In my case it is
>> > not really driven by a gpio but by a pio from the sdhci device. In the binding,
>> What's a "pio"?
>> What do you mean by the it's driven from the sdhci device?
> Sorry I mean sdhci device from the SoC point of view, I should say
> controller. So yes the signal is driven by the controller.
>> Is it the internal HW logic of the sdhci controller that manages the
>> IO voltage? And this logic can be controlled via certain register bits
>> in the SDHCI controller?
> Yes, it depends of the value of the '1.8V Signaling Enable' value in the
> host control 2 register.
>> > declaring the gpio is an option so I thought using this regulator fits my need.
>> In quite many cases it makes sense to model this though a gpio
>> regulator. For example when you use a level shifter circuit. Those
>> normally have gpio pin routed to control the voltage level output for
>> the signals. For example switching between 1.8V and 2.9V.
> I agree, my concern is to know if I can consider it as a 'general' pio
> since it is driven by the sdhci controller.

This doesn't seems like a case where a gpio regulator should be used
and I am not sure what problem it would solve. Beside to suppress the
log warnings (actually those aren't warnings but informations).

Isn't sdhci_do_start_signal_voltage_switch() doing what you need here?

Kind regards

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