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 <[email protected]>
---
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
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 <[email protected]>
Reviewed-by: Heikki Krogerus <[email protected]>
> ---
> 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