diff options
Diffstat (limited to 'common/charge_ramp.c')
| -rw-r--r-- | common/charge_ramp.c | 21 |
1 files changed, 17 insertions, 4 deletions
diff --git a/common/charge_ramp.c b/common/charge_ramp.c index a408771f40..32e0d21ddb 100644 --- a/common/charge_ramp.c +++ b/common/charge_ramp.c @@ -18,16 +18,29 @@ test_mockable int chg_ramp_allowed(int port, int supplier) return 0; switch (supplier) { - /* Use ramping for USB-C DTS suppliers (debug accessory eg suzy-q). */ + /* + * Use ramping for USB-C DTS suppliers (debug accessory eg suzy-q). + * The suzy-q simply passes through the VBUS. The power supplier behind + * may be a SDP/CDP which requires ramping. + */ case CHARGE_SUPPLIER_TYPEC_DTS: return 1; /* - * Use HW ramping for USB-C chargers. Don't use SW ramping since the - * slow ramp causes issues with auto power on (b/169634979). + * Don't regulate the input voltage for USB-C chargers. It is + * unnecessary as the USB-C compliant adapters should never trigger it + * active. + * + * The USB-C spec defines their load curves should not be below + * 4.75V @0A and 4V @3A. We can't define the voltage regulation value + * higher than 4V since it limits the current reaching its max 3A. If + * we define the voltage regulation value lower than 4V, their load + * curves will never be below the voltage regulation line. + * + * Check go/charge_ramp_typec for detail. */ case CHARGE_SUPPLIER_PD: case CHARGE_SUPPLIER_TYPEC: - return IS_ENABLED(CONFIG_CHARGE_RAMP_HW); + return 0; /* default: fall through */ } |