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

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Message-ID: <CAPTae5Lz3dW6Qw4izJFa7XGiBHmRr24vPWkoieijWd0TaLUBCA@mail.gmail.com>
Date: Tue, 23 Jan 2024 03:58:30 -0800
From: Badhri Jagan Sridharan <badhri@...gle.com>
To: Gábor Stefanik <netrolller.3d@...il.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"

Hi Gabor,

While HI-Zing CC pins disrupts power for batteryless devices, not
Hi-Zing CC pins would prevent clean error recovery for self powered
devices.
Hi-Zing CC pins would make the port partner recognize it as disconnect
and will result in bringup the connection back cleanly.

How about leveraging "self-powered" device tree property and Hi-Zing
CC pins only when using "self-powered" ?

Regards,
Badhri

On Wed, Jan 17, 2024 at 8:07 AM Gábor Stefanik <netrolller.3d@...il.com> wrote:
>
> 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
> >
> >