A USB-C hard reset involves removing the voltage from VBUS for some time. So basically it has the same effect as removing the USB-C plug for a short moment. If the machine is powered from the USB-C port and does not have a fallback supply (e.g. a battery), this will result in a full machine reset due to power loss. Ideally we want to avoid triggering a hard reset on these boards. A non-working USB-C port is probably better than unplanned reboots. But boards with a backup supply should do the hard reset to get everything working again. In theory it would be enough to check the self_powered property, but it seems the property might not be configured consistently enough in system firmwares. So let's start with just printing an error message when a hard reset is triggered on systems we expect to be affected. This at least makes debugging issues on affected systems easier without impacting unaffected systems too much. Signed-off-by: Sebastian Reichel <sebastian.reichel@xxxxxxxxxxxxx> --- drivers/usb/typec/tcpm/tcpm.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c index 8a1af08f71b6..375bc84d14a2 100644 --- a/drivers/usb/typec/tcpm/tcpm.c +++ b/drivers/usb/typec/tcpm/tcpm.c @@ -5185,6 +5185,8 @@ static void run_state_machine(struct tcpm_port *port) case HARD_RESET_SEND: if (port->ams != NONE_AMS) tcpm_ams_finish(port); + if (!port->self_powered && port->port_type == TYPEC_PORT_SNK) + dev_err(port->dev, "Initiating hard-reset, which might result in machine power-loss.\n"); /* * State machine will be directed to HARD_RESET_START, * thus set upcoming_state to INVALID_STATE. -- 2.43.0
