nx20p3483: Fix VBUS OVLO threshold and dead battery mode check

If the board is not powered until VBUS is connected, then that port
will trigger dead battery mode in the PPC. This mode must be exited by
the host (EC) writing to the control register. Until dead battery mode
is exited, VBUS OVLO is fixed at 6.8V. Therefore the regular setting
of this value must be done after exiting dead battery mode.

This CL also changes the check for dead battery mode to use the mode
value in the device status register. The bit in the control register
does not reflect the status, but rather, if dead battery mode exit has
been written by the host. The current check will result in the dead
battery mode section being executed for both ports after every power
up. However, only the port that has VBUS active would succeed because
the HV_SNK mode can't be enabled unless VBUS is present.

Lastly, this CL changes the verification check for the
sink/source_enable functions to rely on the mode in the device status
register instead of the switch state. The reason for this is that the
switch state requires ~15 msec delay before it gets updated following
SNK_EN to the nx20p3484 being set high. However, the mode reports the
correct state without reqiuring a msleep.

BUG=b:77561535
BRANCH=NONE
TEST=Tested both port 0 and 1 and verified that Yorp can power up
without a battery. In addition verified that
nx20p3483_vbus_sink_enable returns EC_SUCCESS for both enable/disable
cases.

Change-Id: I2c993b592cd30e34a39d1c1b7e3c54be9f505844
Signed-off-by: Scott Collyer <scollyer@google.com>
Reviewed-on: https://chromium-review.googlesource.com/1005621
Commit-Ready: Scott Collyer <scollyer@chromium.org>
Tested-by: Scott Collyer <scollyer@chromium.org>
Reviewed-by: Jett Rink <jettrink@chromium.org>

0 files changed, 0 insertions, 0 deletions