tcpc/rt1718s: disable FRS until valid FRS VBUS drop

`rt1718s_set_frs_enable` does three things:
 1. enable/disable FRS RX detection
 2. enable/disable auto asserting EN_SRC when FRS happened
 3. enable/disable EN_FRS

RT1718S EN_SRC GPIO auto-enablement is only working when
EN_FRS is asserted and the VBUS drop below Vsafe5VMax.
However, some of the FRS hubs have a higher capacitance, and
this makes the VBUS discharging slowly, and currently, EN_FRS is
disabled after we got FRS RX signal on CC line, and it might happen
before the VBUS discharged to Vsafe5VMax, and the FRS won't source
in that case because EN_FRS was deasserted at the moment.

Also, some of the PPC (e.g. nx20p348x and hl5099) requiring the EN_FRS
asserting longer even after the EN_SRC asserted (power is sourcing), so
that the VBUS can be maintained.

To fix these issues, we defer deasserting the EN_FRS for 5ms after RT1718S
reports VBUS valid low (4.75V), and EN_SRC is asserted. The 5ms is
recommended by HL5099 vendor to maintain the VBUS.

BUG=b:223086905 b/228422539
TEST=kingler C1 FRS works
BRANCH=none

Change-Id: Idc1fc8614b30275b825a655d7af821c1a1c99ee0
Signed-off-by: Eric Yilun Lin <yllin@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3544748
Auto-Submit: Eric Yilun Lin <yllin@google.com>
Reviewed-by: Ting Shen <phoenixshen@chromium.org>
Tested-by: Eric Yilun Lin <yllin@google.com>
Commit-Queue: Ting Shen <phoenixshen@chromium.org>

0 files changed, 0 insertions, 0 deletions