linux-kernel - Re: [PATCH v1] Revert "usb: typec: tcpm: fix cc role at port reset"

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Date: Wed, 17 Jan 2024 17:07:20 +0100
From: Gábor Stefanik <netrolller.3d@...il.com>
To: Badhri Jagan Sridharan <badhri@...gle.com>
Cc: gregkh@...uxfoundation.org, linux@...ck-us.net, 
	heikki.krogerus@...ux.intel.com, kyletso@...gle.com, 
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org, rdbabiera@...gle.com, 
	amitsd@...gle.com, stable@...r.kernel.org, stable@...nel.org
Subject: Re: [PATCH v1] Revert "usb: typec: tcpm: fix cc role at port reset"

This will break operation of batteryless devices relying on a USB
Type-C port for their power needs, as the port reset upon controller
initialization will cause power to be cut to the device, resulting in
a boot loop.
Devices using the FUSB302C port controller are especially severely
affected, as upon losing power, this controller can retain CC states
for a very long time (potentially forever if some parasitic source of
power is present), requiring a full mechanical disconnect-reconnect
cycle before the device receives power again.

While the USB Type C specification does require this behavior, I would
consider this an oversight in the standard (perhaps left over from
when USB Power Delivery was still going to be USB Battery Charging
2.0).

Badhri Jagan Sridharan <badhri@...gle.com> ezt írta (időpont: 2024.
jan. 17., Sze, 12:38):
>
> This reverts commit 1e35f074399dece73d5df11847d4a0d7a6f49434.
>
> Given that ERROR_RECOVERY calls into PORT_RESET for Hi-Zing
> the CC pins, setting CC pins to default state during PORT_RESET
> breaks error recovery.
>
> 4.5.2.2.2.1 ErrorRecovery State Requirements
> The port shall not drive VBUS or VCONN, and shall present a
> high-impedance to ground (above zOPEN) on its CC1 and CC2 pins.
>
> Hi-Zing the CC pins is the inteded behavior for PORT_RESET.
> CC pins are set to default state after tErrorRecovery in
> PORT_RESET_WAIT_OFF.
>
> 4.5.2.2.2.2 Exiting From ErrorRecovery State
> A Sink shall transition to Unattached.SNK after tErrorRecovery.
> A Source shall transition to Unattached.SRC after tErrorRecovery.
>
> Cc: stable@...nel.org
> Fixes: 1e35f074399d ("usb: typec: tcpm: fix cc role at port reset")
> Signed-off-by: Badhri Jagan Sridharan <badhri@...gle.com>
> ---
>  drivers/usb/typec/tcpm/tcpm.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
> index 5945e3a2b0f7..9d410718eaf4 100644
> --- a/drivers/usb/typec/tcpm/tcpm.c
> +++ b/drivers/usb/typec/tcpm/tcpm.c
> @@ -4876,8 +4876,7 @@ static void run_state_machine(struct tcpm_port *port)
>                 break;
>         case PORT_RESET:
>                 tcpm_reset_port(port);
> -               tcpm_set_cc(port, tcpm_default_state(port) == SNK_UNATTACHED ?
> -                           TYPEC_CC_RD : tcpm_rp_cc(port));
> +               tcpm_set_cc(port, TYPEC_CC_OPEN);
>                 tcpm_set_state(port, PORT_RESET_WAIT_OFF,
>                                PD_T_ERROR_RECOVERY);
>                 break;
>
> base-commit: 933bb7b878ddd0f8c094db45551a7daddf806e00
> --
> 2.43.0.429.g432eaa2c6b-goog
>
>