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Message-ID: <0e516c19-31f9-c2a7-97da-7c61e5d1d3f0@roeck-us.net>
Date: Sat, 10 Dec 2022 01:58:53 -0800
From: Guenter Roeck <linux@...ck-us.net>
To: Badhri Jagan Sridharan <badhri@...gle.com>,
Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
Kyle Tso <kyletso@...gle.com>
Subject: Re: [PATCH v9 1/3] usb: typec: tcpm: Add callbacks to mitigate
wakeups due to contaminant
On 12/9/22 22:16, Badhri Jagan Sridharan wrote:
> On some of the TCPC implementations, when the Type-C port is exposed
> to contaminants, such as water, TCPC stops toggling while reporting OPEN
> either by the time TCPM reads CC pin status or during CC debounce
> window. This causes TCPM to be stuck in TOGGLING state. If TCPM is made
> to restart toggling, the behavior recurs causing redundant CPU wakeups
> till the USB-C port is free of contaminant.
>
> [206199.287817] CC1: 0 -> 0, CC2: 0 -> 0 [state TOGGLING, polarity 0, disconnected]
> [206199.640337] CC1: 0 -> 0, CC2: 0 -> 0 [state TOGGLING, polarity 0, disconnected]
> [206199.985789] CC1: 0 -> 0, CC2: 0 -> 0 [state TOGGLING, polarity 0, disconnected]
>
> (or)
>
> [ 7853.867577] Start toggling
> [ 7853.889921] CC1: 0 -> 0, CC2: 0 -> 0 [state TOGGLING, polarity 0, disconnected]
> [ 7855.698765] CC1: 0 -> 0, CC2: 0 -> 5 [state TOGGLING, polarity 0, connected]
> [ 7855.698790] state change TOGGLING -> SNK_ATTACH_WAIT [rev3 NONE_AMS]
> [ 7855.698826] pending state change SNK_ATTACH_WAIT -> SNK_DEBOUNCED @ 170 ms [rev3 NONE_AMS]
> [ 7855.703559] CC1: 0 -> 0, CC2: 5 -> 5 [state SNK_ATTACH_WAIT, polarity 0, connected]
> [ 7855.856555] CC1: 0 -> 0, CC2: 5 -> 0 [state SNK_ATTACH_WAIT, polarity 0, disconnected]
> [ 7855.856581] state change SNK_ATTACH_WAIT -> SNK_ATTACH_WAIT [rev3 NONE_AMS]
> [ 7855.856613] pending state change SNK_ATTACH_WAIT -> SNK_UNATTACHED @ 170 ms [rev3 NONE_AMS]
> [ 7856.027744] state change SNK_ATTACH_WAIT -> SNK_UNATTACHED [delayed 170 ms]
> [ 7856.181949] CC1: 0 -> 0, CC2: 0 -> 0 [state TOGGLING, polarity 0, disconnected]
> [ 7856.187896] CC1: 0 -> 0, CC2: 0 -> 0 [state TOGGLING, polarity 0, disconnected]
> [ 7857.645630] CC1: 0 -> 0, CC2: 0 -> 0 [state TOGGLING, polarity 0, disconnected]
> [ 7857.647291] CC1: 0 -> 0, CC2: 0 -> 5 [state TOGGLING, polarity 0, connected]
> [ 7857.647298] state change TOGGLING -> SNK_ATTACH_WAIT [rev3 NONE_AMS]
> [ 7857.647310] pending state change SNK_ATTACH_WAIT -> SNK_DEBOUNCED @ 170 ms [rev3 NONE_AMS]
> [ 7857.808106] CC1: 0 -> 0, CC2: 5 -> 0 [state SNK_ATTACH_WAIT, polarity 0, disconnected]
> [ 7857.808123] state change SNK_ATTACH_WAIT -> SNK_ATTACH_WAIT [rev3 NONE_AMS]
> [ 7857.808150] pending state change SNK_ATTACH_WAIT -> SNK_UNATTACHED @ 170 ms [rev3 NONE_AMS]
> [ 7857.978727] state change SNK_ATTACH_WAIT -> SNK_UNATTACHED [delayed 170 ms]
>
> To mitigate redundant TCPM wakeups, TCPCs which do have the needed hardware
> can implement the check_contaminant callback which is invoked by TCPM
> to evaluate for presence of contaminant. Lower level TCPC driver can
> restart toggling through TCPM_PORT_CLEAN event when the driver detects
> that USB-C port is free of contaminant. check_contaminant callback also passes
> the disconnect_while_debounce flag which when true denotes that the CC pins
> transitioned to OPEN state during the CC debounce window.
>
> Signed-off-by: Badhri Jagan Sridharan <badhri@...gle.com>
> ---
> Changes since v7:
> * None. Skipped versions by mistake.
> Changes since v6:
> * folded the debounce logic into tcpm state machine and removed tcpm
> * state export.
> * Added a helper to determine whether the port is in toggling state.
> * Excluded CHECK_CONTAMINANT from tcpm_log.
> Changes since v5:
> * Updated commit message. Removed change id.
> Changes since v4:
> * None
> Changes since v3:
> * None
> Changes since V2:
> * Offloaded tcpm from maintaining disconnect_while_debouncing logic
> * to lower level maxim tcpc driver based on feedback.
> ---
> drivers/usb/typec/tcpm/tcpm.c | 51 ++++++++++++++++++++++++++++++++++-
> include/linux/usb/tcpm.h | 8 ++++++
> 2 files changed, 58 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
> index 904c7b4ce2f0..5f514e5e6e2a 100644
> --- a/drivers/usb/typec/tcpm/tcpm.c
> +++ b/drivers/usb/typec/tcpm/tcpm.c
> @@ -36,6 +36,7 @@
> #define FOREACH_STATE(S) \
> S(INVALID_STATE), \
> S(TOGGLING), \
> + S(CHECK_CONTAMINANT), \
> S(SRC_UNATTACHED), \
> S(SRC_ATTACH_WAIT), \
> S(SRC_ATTACHED), \
> @@ -249,6 +250,7 @@ enum frs_typec_current {
> #define TCPM_RESET_EVENT BIT(2)
> #define TCPM_FRS_EVENT BIT(3)
> #define TCPM_SOURCING_VBUS BIT(4)
> +#define TCPM_PORT_CLEAN BIT(5)
>
> #define LOG_BUFFER_ENTRIES 1024
> #define LOG_BUFFER_ENTRY_SIZE 128
> @@ -483,6 +485,13 @@ struct tcpm_port {
> * SNK_READY for non-pd link.
> */
> bool slow_charger_loop;
> +
> + /*
> + * When true indicates that the lower level drivers indicate potential presence
> + * of contaminant in the connector pins based on the tcpm state machine
> + * transitions.
> + */
> + bool potential_contaminant;
> #ifdef CONFIG_DEBUG_FS
> struct dentry *dentry;
> struct mutex logbuffer_lock; /* log buffer access lock */
> @@ -647,7 +656,7 @@ static void tcpm_log(struct tcpm_port *port, const char *fmt, ...)
> /* Do not log while disconnected and unattached */
> if (tcpm_port_is_disconnected(port) &&
> (port->state == SRC_UNATTACHED || port->state == SNK_UNATTACHED ||
> - port->state == TOGGLING))
> + port->state == TOGGLING || port->state == CHECK_CONTAMINANT))
> return;
>
> va_start(args, fmt);
> @@ -3904,15 +3913,28 @@ static void run_state_machine(struct tcpm_port *port)
> unsigned int msecs;
> enum tcpm_state upcoming_state;
>
> + if (port->tcpc->check_contaminant && port->state != CHECK_CONTAMINANT)
> + port->potential_contaminant = ((port->enter_state == SRC_ATTACH_WAIT &&
> + port->state == SRC_UNATTACHED) ||
> + (port->enter_state == SNK_ATTACH_WAIT &&
> + port->state == SNK_UNATTACHED));
> +
> port->enter_state = port->state;
> switch (port->state) {
> case TOGGLING:
> break;
> + case CHECK_CONTAMINANT:
> + port->tcpc->check_contaminant(port->tcpc);
> + break;
> /* SRC states */
> case SRC_UNATTACHED:
> if (!port->non_pd_role_swap)
> tcpm_swap_complete(port, -ENOTCONN);
> tcpm_src_detach(port);
> + if (port->potential_contaminant) {
> + tcpm_set_state(port, CHECK_CONTAMINANT, 0);
> + break;
> + }
> if (tcpm_start_toggling(port, tcpm_rp_cc(port))) {
> tcpm_set_state(port, TOGGLING, 0);
> break;
> @@ -4150,6 +4172,10 @@ static void run_state_machine(struct tcpm_port *port)
> tcpm_swap_complete(port, -ENOTCONN);
> tcpm_pps_complete(port, -ENOTCONN);
> tcpm_snk_detach(port);
> + if (port->potential_contaminant) {
> + tcpm_set_state(port, CHECK_CONTAMINANT, 0);
> + break;
> + }
> if (tcpm_start_toggling(port, TYPEC_CC_RD)) {
> tcpm_set_state(port, TOGGLING, 0);
> break;
> @@ -4926,6 +4952,9 @@ static void _tcpm_cc_change(struct tcpm_port *port, enum typec_cc_status cc1,
> else if (tcpm_port_is_sink(port))
> tcpm_set_state(port, SNK_ATTACH_WAIT, 0);
> break;
> + case CHECK_CONTAMINANT:
> + /* Wait for Toggling to be resumed */
> + break;
> case SRC_UNATTACHED:
> case ACC_UNATTACHED:
> if (tcpm_port_is_debug(port) || tcpm_port_is_audio(port) ||
> @@ -5425,6 +5454,11 @@ static void tcpm_pd_event_handler(struct kthread_work *work)
> port->vbus_source = true;
> _tcpm_pd_vbus_on(port);
> }
> + if (events & TCPM_PORT_CLEAN) {
> + tcpm_log(port, "port clean");
> + if (port->state == CHECK_CONTAMINANT)
> + tcpm_set_state(port, TOGGLING, 0);
> + }
>
I just realized: This never calls tcpm_start_toggling(), meaning the
start_toggling() callback will never be called. Worse, if the callback
doesn't exist the state machine may be stuck. How does the state machine
ever really start toggling in this situation ?
Thanks,
Guenter
> spin_lock(&port->pd_event_lock);
> }
> @@ -5477,6 +5511,21 @@ void tcpm_sourcing_vbus(struct tcpm_port *port)
> }
> EXPORT_SYMBOL_GPL(tcpm_sourcing_vbus);
>
> +void tcpm_port_clean(struct tcpm_port *port)
> +{
> + spin_lock(&port->pd_event_lock);
> + port->pd_events |= TCPM_PORT_CLEAN;
> + spin_unlock(&port->pd_event_lock);
> + kthread_queue_work(port->wq, &port->event_work);
> +}
> +EXPORT_SYMBOL_GPL(tcpm_port_clean);
> +
> +bool tcpm_port_is_toggling(struct tcpm_port *port)
> +{
> + return port->port_type == TYPEC_PORT_DRP && port->state == TOGGLING;
> +}
> +EXPORT_SYMBOL_GPL(tcpm_port_is_toggling);
> +
> static void tcpm_enable_frs_work(struct kthread_work *work)
> {
> struct tcpm_port *port = container_of(work, struct tcpm_port, enable_frs);
> diff --git a/include/linux/usb/tcpm.h b/include/linux/usb/tcpm.h
> index bffc8d3e14ad..ab7ca872950b 100644
> --- a/include/linux/usb/tcpm.h
> +++ b/include/linux/usb/tcpm.h
> @@ -114,6 +114,11 @@ enum tcpm_transmit_type {
> * Optional; The USB Communications Capable bit indicates if port
> * partner is capable of communication over the USB data lines
> * (e.g. D+/- or SS Tx/Rx). Called to notify the status of the bit.
> + * @check_contaminant:
> + * Optional; The callback is called when CC pins report open status
> + * at the end of the deboumce period or when the port is still
> + * toggling. Chip level drivers are expected to check for contaminant
> + * and call tcpm_clean_port when the port is clean.
> */
> struct tcpc_dev {
> struct fwnode_handle *fwnode;
> @@ -148,6 +153,7 @@ struct tcpc_dev {
> bool pps_active, u32 requested_vbus_voltage);
> bool (*is_vbus_vsafe0v)(struct tcpc_dev *dev);
> void (*set_partner_usb_comm_capable)(struct tcpc_dev *dev, bool enable);
> + void (*check_contaminant)(struct tcpc_dev *dev);
> };
>
> struct tcpm_port;
> @@ -165,5 +171,7 @@ void tcpm_pd_transmit_complete(struct tcpm_port *port,
> enum tcpm_transmit_status status);
> void tcpm_pd_hard_reset(struct tcpm_port *port);
> void tcpm_tcpc_reset(struct tcpm_port *port);
> +void tcpm_port_clean(struct tcpm_port *port);
> +bool tcpm_port_is_toggling(struct tcpm_port *port);
>
> #endif /* __LINUX_USB_TCPM_H */
>
> base-commit: 1524ceb14dd5ebd6f724d993c5ec1a9a8d445d8e
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