[U-Boot] [linux-sunxi] [PATCH v3 0/9] Stop AXP from crashing when enabling LDO3

[Jagan Teki]

On Wed, Nov 21, 2018 at 11:35 PM Priit Laes <plaes at 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 <oliver at schinagl.nl>
> Signed-off-by: Priit Laes <plaes at 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

Applied to u-boot-sunxi/master