On Wed, Nov 21, 2018 at 08:05:31PM +0200, Priit Laes wrote: > From: Olliver Schinagl <[email protected]> > > Some boards feature a capacitance on LDO3's output that is too large, > causing inrush currents which as a result, shut down the AXP209. This > has been reported before, without knowing the actual cause. > > A fix appeared to be done with > commit 0e6e34ac8dbb ("sunxi: Olimex A20 boards: Enable LDO3 and LDO4 > regulators"). > > The description there is a bit misleading, the kernel does not hang > during AXP209 initialization, the PMIC shuts down, causing voltages to > drop and thus the whole system freezes. > > While the AXP209 does have the ability to ramp up the voltage slowly, to > reduce these inrush currents, the voltage rate control (VRC) however is > not applicable when switching on the LDO3 output. Only when going from > an enabled lower voltage setting, to a higher voltage setting is the VRC > in effect. > > To work around this problem, we set LDO3 to the lowest possible setting > of 0.7 V if it was not yet enabled, and then let the VRC (if enabled) do > its thing. It should be noted, that for some undocumented reason, there > is a short delay needed between setting the LDO3 voltage register and > enabling the power. One would expect that this delay ought to be just > after enabling the output power at 0.7 V, but this did not work. > > Signed-off-by: Olliver Schinagl <[email protected]> > Signed-off-by: Priit Laes <[email protected]>
Acked-by: Maxime Ripard <[email protected]> Maxime -- Maxime Ripard, Bootlin Embedded Linux and Kernel engineering https://bootlin.com -- You received this message because you are subscribed to the Google Groups "linux-sunxi" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
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