regulator: ti-abb: Fix bias voltage glitch in transition to bypass mode
authorNishanth Menon <nm@ti.com>
Fri, 27 Sep 2013 13:25:14 +0000 (08:25 -0500)
committerMark Brown <broonie@linaro.org>
Fri, 27 Sep 2013 14:02:04 +0000 (15:02 +0100)
commitbf00ca35cec8f0894dcfd90f88b03af1d5c7b86f
tree8a82cb3669f55f8eb6ddafced018b9d4ea7e218a
parent4a10c2ac2f368583138b774ca41fac4207911983
regulator: ti-abb: Fix bias voltage glitch in transition to bypass mode

As documented in Application Note SWPA117 v2.1(NDA), LDO override has a
requirement that when switching from Bias active + override active
mode(FBB/RBB) to Bypass(nominal) mode, LDO reset must be performed
*after* LDO transitions to Bypass(nominal) mode.

The same rule in reverse applies when switching from a ABB bypass mode
to ABB enabled - LDO override *must* be performed prior to transition to
required ABB mode, if we do not do that, the same glitch takes place.

Currently while transitioning to ABB bypass, we reset the LDO overide
prior to the transition which causes a few milliseconds where ABB LDO
voltage could go all the way to 800mV(based on SoC process node),
during this period, the delta voltage between VDD rail and VBB rail
could cause the system to improperly function.

Signed-off-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Mark Brown <broonie@linaro.org>
Cc: stable@vger.kernel.org
drivers/regulator/ti-abb-regulator.c