On Thu, May 23, 2024 at 07:12:29PM +0200, Sebastian Reichel wrote: > 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> Reviewed-by: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx> > --- > 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 -- heikki
