diff options
| -rw-r--r-- | zephyr/Kconfig.charger | 6 | ||||
| -rw-r--r-- | zephyr/program/nissa/src/common.c | 39 |
2 files changed, 45 insertions, 0 deletions
diff --git a/zephyr/Kconfig.charger b/zephyr/Kconfig.charger index 35bd8590ab..c2c6eeb3f4 100644 --- a/zephyr/Kconfig.charger +++ b/zephyr/Kconfig.charger @@ -204,6 +204,12 @@ config PLATFORM_EC_CHARGER_SM5803 Enables the driver for the SM5803. The SM5803 is the Silicon Mitus SM5803 Buck-Boost Charger. + This charger is known to be very inefficient when operating in buck-boost + mode (when input voltage is close to output voltage), such that permanent + damage may be done to the charger. Users should exercise caution around + choice of supported configurations: see b:260271871, b:258754576, and + b:230712704 for more information. + if PLATFORM_EC_OCPC diff --git a/zephyr/program/nissa/src/common.c b/zephyr/program/nissa/src/common.c index 119a999736..155dc541d4 100644 --- a/zephyr/program/nissa/src/common.c +++ b/zephyr/program/nissa/src/common.c @@ -148,3 +148,42 @@ __override void ocpc_get_pid_constants(int *kp, int *kp_div, int *ki, *kd = 0; *kd_div = 1; } + +#ifdef CONFIG_PLATFORM_EC_CHARGER_SM5803 +/* + * Called by USB-PD code to determine whether a given input voltage is + * acceptable. + */ +__override int pd_is_valid_input_voltage(int mv) +{ + int battery_voltage, rv; + + rv = battery_design_voltage(&battery_voltage); + if (rv) { + LOG_ERR("Unable to get battery design voltage: %d", rv); + return true; + } + + /* + * SM5803 is extremely inefficient in buck-boost mode, when + * VBUS ~= VSYS: very high temperatures on the chip and associated + * inductor have been observed when sinking normal charge current in + * buck-boost mode (but not in buck or boost mode) so we choose to + * completely exclude some voltages that are likely to be problematic. + * + * Nissa devices use either 2S or 3S batteries, for which VBUS will + * usually only be near VSYS with a 3S battery and 12V input (picked + * from among common supported PD voltages)- 2S can get close to + * 9V, but we expect charge current to be low when a 2S battery is + * charged to that voltage (because it will be nearly full). + * + * We assume that any battery with a design voltage above 9V is 3S, and + * that other problematic PD voltages (near to, but not exactly 12V) + * will rarely occur. + */ + if (battery_voltage > 9000 && mv == 12000) { + return false; + } + return true; +} +#endif |