[PATCH] mmc: dw_mmc: try pick the exact same voltage as vmmc for vqmmc
Doug Anderson
dianders at chromium.org
Fri Nov 21 09:42:08 PST 2014
Ulf,
On Fri, Nov 21, 2014 at 4:06 AM, Ulf Hansson <ulf.hansson at linaro.org> wrote:
> [...]
>
>> Sure
>> If the first card is sd2.0 since startup, dw_mci_switch_voltage will not be called,
>
> That can't be right. mmc_power_up() should trigger
> dw_mci_switch_voltage() to be invoked.
Hmmm, I think you're right. Addy: can you double check if it's only
the 2nd card for you? I was thinking that if a regulator is currently
3.3V and you request 2.7 - 3.3V the regulator framework will treat
that as a noop. ...but that definitely doesn't appear to be the case.
When I boot up the first time even with no SD card plugged in, I see
this at bootup:
[ 3.042234] vccio_sd: 1800 <--> 3300 mV at 3300 mV
...showing that it started at 3.3V. Then I see:
$ grep "" /sys/class/regulator/regulator.16/{name,microvolts}
/sys/class/regulator/regulator.16/name:vccio_sd
/sys/class/regulator/regulator.16/microvolts:2700000
...so it is certainly getting changed even with no card plugged in.
BTW: I don't actually have one of these failing cards--all of mine
work. Addy, do you know the make and model of the card you have that
fails?
-Doug
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