On Wed, Nov 21, 2018 at 11:35 PM Priit Laes <pl...@plaes.org> wrote: > > This is a resend/v2 of a "Stop AXP from crashing when enabling LDO3" series, > posted by Olliver Schinagl in March 2017. Unfortunately it never got past > initial discussion [1], but most Olimex Lime2 boards are still running > into this bug. > > When powering up an AXP209, the default value for LDO3 output is enabled. This > works fine. However if for whatever reason, LDO3 is disabled, for example by > OS > during reboot and u-boot enables LDO3 again, the PMIC shuts down (without > setting an interrupt) causing the board to hang. This behavior has been seen > from Linux as well, u-boot disables LDO3 as a default value, the kernel > enables > it per its DTS, the kernel hangs as the PMIC gets shut down. > > The root cause is that some boards have too high capacitance on the LDO3 > output > port causing inrush currents exceeding the maximum of the AXP209. > > The fix is to turn on the LDO3 at the lowest possible voltage and then set the > final voltage. > > If the capacitance is really big (due to a connected device for example) the > AXP209 also features VRC, or Voltage Rate Control, allowing voltage to ramp up > even slower. > > Similar changes need to be also implemented in the operating system driver > side when driver needs to toggle power for the ALDO3 regulator. > > This patch series implements the above with a few tiny cleanups. > > The initial discussion with some scope screenshots can be found in the > linux-sunxi mailing list [0]. > > And the initial series were posted to u-boot mailing list [1]. > > Signed-off-by: Olliver Schinagl <oli...@schinagl.nl> > Signed-off-by: Priit Laes <pl...@plaes.org> > > [0] https://groups.google.com/forum/m/#!topic/linux-sunxi/EDvEsbHHqQI > [1] https://lists.denx.de/pipermail/u-boot/2017-March/282789.html
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