[PATCH] mmc: dw_mmc: try pick the exact same voltage as vmmc for vqmmc
ulf.hansson at linaro.org
Fri Nov 21 04:06:18 PST 2014
> 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.
> and card can be identified. But if UHS card is pulgged in first, the vqmmc will be down to 1.8v.
> when sd2.0 card is pulgged in, mmc core will call dw_mci_switch_voltage to change vqmmc to 3.3v
> (MMC_SINGLE_VOTAGE_330). So vqmmc will be set 2.7v, if we request 2.7-3.6v.
> But vmmc is always 3.3v,becuase it be set min_volt = max_volt = 3.3v in dt tables.
> So the result:
> vmmc = 3.3v and vqmmc = 2.7v, and sd2.0 card is failed to identify in my test.
Hmm. I wonder why it works the first time? Could it be that your
regulator have voltage ramp up time that isn't properly considered?
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