Re: [PATCH v6 1/3] usb: typec: tcpm: Add callbacks to mitigate wakeups due to contaminant

From: Badhri Jagan Sridharan
Date: Sat Dec 10 2022 - 01:06:48 EST

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On Fri, Dec 9, 2022 at 5:44 AM Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
>
> On 12/8/22 18:39, Badhri Jagan Sridharan wrote:
> > On Thu, Dec 8, 2022 at 3:56 PM Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
> >>
> >> On 12/8/22 07:04, 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]
> >>> ...
> >>>
> >>> TCPM invokes is_potential_contaminant callback to allow low level chip
> >>> drivers to monitor TCPM state machine transitions and notify TCPM when
> >>> the Type-C port needs to be checked for potential contaminant presence.
> >>> 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.
> >>>
> >>> Signed-off-by: Badhri Jagan Sridharan <badhri@xxxxxxxxxx>
> >>> ---
> >>> 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 | 162 +++++++++-------------------------
> >>> include/linux/usb/tcpm.h | 133 ++++++++++++++++++++++++++++
> >>> 2 files changed, 177 insertions(+), 118 deletions(-)
> >>>
> >>> diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
> >>> index 904c7b4ce2f0..a138cea49612 100644
> >>> --- a/drivers/usb/typec/tcpm/tcpm.c
> >>> +++ b/drivers/usb/typec/tcpm/tcpm.c
> >>> @@ -33,119 +33,6 @@
> >>>
> >>> #include <uapi/linux/sched/types.h>
> >>>
> >>> -#define FOREACH_STATE(S) \
> >>> - S(INVALID_STATE), \
> >>> - S(TOGGLING), \
> >>> - S(SRC_UNATTACHED), \
> >>> - S(SRC_ATTACH_WAIT), \
> >>> - S(SRC_ATTACHED), \
> >>> - S(SRC_STARTUP), \
> >>> - S(SRC_SEND_CAPABILITIES), \
> >>> - S(SRC_SEND_CAPABILITIES_TIMEOUT), \
> >>> - S(SRC_NEGOTIATE_CAPABILITIES), \
> >>> - S(SRC_TRANSITION_SUPPLY), \
> >>> - S(SRC_READY), \
> >>> - S(SRC_WAIT_NEW_CAPABILITIES), \
> >>> - \
> >>> - S(SNK_UNATTACHED), \
> >>> - S(SNK_ATTACH_WAIT), \
> >>> - S(SNK_DEBOUNCED), \
> >>> - S(SNK_ATTACHED), \
> >>> - S(SNK_STARTUP), \
> >>> - S(SNK_DISCOVERY), \
> >>> - S(SNK_DISCOVERY_DEBOUNCE), \
> >>> - S(SNK_DISCOVERY_DEBOUNCE_DONE), \
> >>> - S(SNK_WAIT_CAPABILITIES), \
> >>> - S(SNK_NEGOTIATE_CAPABILITIES), \
> >>> - S(SNK_NEGOTIATE_PPS_CAPABILITIES), \
> >>> - S(SNK_TRANSITION_SINK), \
> >>> - S(SNK_TRANSITION_SINK_VBUS), \
> >>> - S(SNK_READY), \
> >>> - \
> >>> - S(ACC_UNATTACHED), \
> >>> - S(DEBUG_ACC_ATTACHED), \
> >>> - S(AUDIO_ACC_ATTACHED), \
> >>> - S(AUDIO_ACC_DEBOUNCE), \
> >>> - \
> >>> - S(HARD_RESET_SEND), \
> >>> - S(HARD_RESET_START), \
> >>> - S(SRC_HARD_RESET_VBUS_OFF), \
> >>> - S(SRC_HARD_RESET_VBUS_ON), \
> >>> - S(SNK_HARD_RESET_SINK_OFF), \
> >>> - S(SNK_HARD_RESET_WAIT_VBUS), \
> >>> - S(SNK_HARD_RESET_SINK_ON), \
> >>> - \
> >>> - S(SOFT_RESET), \
> >>> - S(SRC_SOFT_RESET_WAIT_SNK_TX), \
> >>> - S(SNK_SOFT_RESET), \
> >>> - S(SOFT_RESET_SEND), \
> >>> - \
> >>> - S(DR_SWAP_ACCEPT), \
> >>> - S(DR_SWAP_SEND), \
> >>> - S(DR_SWAP_SEND_TIMEOUT), \
> >>> - S(DR_SWAP_CANCEL), \
> >>> - S(DR_SWAP_CHANGE_DR), \
> >>> - \
> >>> - S(PR_SWAP_ACCEPT), \
> >>> - S(PR_SWAP_SEND), \
> >>> - S(PR_SWAP_SEND_TIMEOUT), \
> >>> - S(PR_SWAP_CANCEL), \
> >>> - S(PR_SWAP_START), \
> >>> - S(PR_SWAP_SRC_SNK_TRANSITION_OFF), \
> >>> - S(PR_SWAP_SRC_SNK_SOURCE_OFF), \
> >>> - S(PR_SWAP_SRC_SNK_SOURCE_OFF_CC_DEBOUNCED), \
> >>> - S(PR_SWAP_SRC_SNK_SINK_ON), \
> >>> - S(PR_SWAP_SNK_SRC_SINK_OFF), \
> >>> - S(PR_SWAP_SNK_SRC_SOURCE_ON), \
> >>> - S(PR_SWAP_SNK_SRC_SOURCE_ON_VBUS_RAMPED_UP), \
> >>> - \
> >>> - S(VCONN_SWAP_ACCEPT), \
> >>> - S(VCONN_SWAP_SEND), \
> >>> - S(VCONN_SWAP_SEND_TIMEOUT), \
> >>> - S(VCONN_SWAP_CANCEL), \
> >>> - S(VCONN_SWAP_START), \
> >>> - S(VCONN_SWAP_WAIT_FOR_VCONN), \
> >>> - S(VCONN_SWAP_TURN_ON_VCONN), \
> >>> - S(VCONN_SWAP_TURN_OFF_VCONN), \
> >>> - \
> >>> - S(FR_SWAP_SEND), \
> >>> - S(FR_SWAP_SEND_TIMEOUT), \
> >>> - S(FR_SWAP_SNK_SRC_TRANSITION_TO_OFF), \
> >>> - S(FR_SWAP_SNK_SRC_NEW_SINK_READY), \
> >>> - S(FR_SWAP_SNK_SRC_SOURCE_VBUS_APPLIED), \
> >>> - S(FR_SWAP_CANCEL), \
> >>> - \
> >>> - S(SNK_TRY), \
> >>> - S(SNK_TRY_WAIT), \
> >>> - S(SNK_TRY_WAIT_DEBOUNCE), \
> >>> - S(SNK_TRY_WAIT_DEBOUNCE_CHECK_VBUS), \
> >>> - S(SRC_TRYWAIT), \
> >>> - S(SRC_TRYWAIT_DEBOUNCE), \
> >>> - S(SRC_TRYWAIT_UNATTACHED), \
> >>> - \
> >>> - S(SRC_TRY), \
> >>> - S(SRC_TRY_WAIT), \
> >>> - S(SRC_TRY_DEBOUNCE), \
> >>> - S(SNK_TRYWAIT), \
> >>> - S(SNK_TRYWAIT_DEBOUNCE), \
> >>> - S(SNK_TRYWAIT_VBUS), \
> >>> - S(BIST_RX), \
> >>> - \
> >>> - S(GET_STATUS_SEND), \
> >>> - S(GET_STATUS_SEND_TIMEOUT), \
> >>> - S(GET_PPS_STATUS_SEND), \
> >>> - S(GET_PPS_STATUS_SEND_TIMEOUT), \
> >>> - \
> >>> - S(GET_SINK_CAP), \
> >>> - S(GET_SINK_CAP_TIMEOUT), \
> >>> - \
> >>> - S(ERROR_RECOVERY), \
> >>> - S(PORT_RESET), \
> >>> - S(PORT_RESET_WAIT_OFF), \
> >>> - \
> >>> - S(AMS_START), \
> >>> - S(CHUNK_NOT_SUPP)
> >>> -
> >>> #define FOREACH_AMS(S) \
> >>> S(NONE_AMS), \
> >>> S(POWER_NEGOTIATION), \
> >>> @@ -182,13 +69,8 @@
> >>> S(COUNTRY_INFO), \
> >>> S(COUNTRY_CODES)
> >>>
> >>> -#define GENERATE_ENUM(e) e
> >>> #define GENERATE_STRING(s) #s
> >>>
> >>> -enum tcpm_state {
> >>> - FOREACH_STATE(GENERATE_ENUM)
> >>> -};
> >>> -
> >>> static const char * const tcpm_states[] = {
> >>> FOREACH_STATE(GENERATE_STRING)
> >>> };
> >>> @@ -249,6 +131,7 @@ 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 +366,14 @@ 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 */
> >>> @@ -3904,15 +3795,26 @@ static void run_state_machine(struct tcpm_port *port)
> >>> unsigned int msecs;
> >>> enum tcpm_state upcoming_state;
> >>>
> >>> + if (port->tcpc->is_potential_contaminant)
> >>> + port->potential_contaminant =
> >>> + port->tcpc->is_potential_contaminant(port->tcpc, port->state);
> >>> +
> >>> 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 && port->tcpc->check_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 +4052,10 @@ 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 && port->tcpc->check_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 +4832,9 @@ 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 +5334,10 @@ 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");
> >>> + tcpm_set_state(port, TOGGLING, 0);
> >>> + }
> >>
> >> That sets the state to TOGGLING unconditionally, even if it not currently
> >> CHECK_CONTAMINANT. Is that a potential problem ?
> >
> > Good catch ! Would make sense to check whether tcpm is in
> > CHECK_CONTAMINANT state before setting the TOGGLING state.
> >>
> >>>
> >>> spin_lock(&port->pd_event_lock);
> >>> }
> >>> @@ -5477,6 +5390,19 @@ void tcpm_sourcing_vbus(struct tcpm_port *port)
> >>> }
> >>> EXPORT_SYMBOL_GPL(tcpm_sourcing_vbus);
> >>>
> >>> +/*
> >>> + * Low level tcpc drivers invoke this once the port is deemed clean to return
> >>> + * the port to TOGGLING state.
> >>> + */
> >>> +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);
> >>> +
> >>> 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..9cf16372a6e4 100644
> >>> --- a/include/linux/usb/tcpm.h
> >>> +++ b/include/linux/usb/tcpm.h
> >>> @@ -10,6 +10,126 @@
> >>> #include <linux/usb/typec.h>
> >>> #include "pd.h"
> >>>
> >>> +#define FOREACH_STATE(S) \
> >>> + S(INVALID_STATE), \
> >>> + S(TOGGLING), \
> >>> + S(CHECK_CONTAMINANT), \
> >>> + S(SRC_UNATTACHED), \
> >>> + S(SRC_ATTACH_WAIT), \
> >>> + S(SRC_ATTACHED), \
> >>> + S(SRC_STARTUP), \
> >>> + S(SRC_SEND_CAPABILITIES), \
> >>> + S(SRC_SEND_CAPABILITIES_TIMEOUT), \
> >>> + S(SRC_NEGOTIATE_CAPABILITIES), \
> >>> + S(SRC_TRANSITION_SUPPLY), \
> >>> + S(SRC_READY), \
> >>> + S(SRC_WAIT_NEW_CAPABILITIES), \
> >>> + \
> >>> + S(SNK_UNATTACHED), \
> >>> + S(SNK_ATTACH_WAIT), \
> >>> + S(SNK_DEBOUNCED), \
> >>> + S(SNK_ATTACHED), \
> >>> + S(SNK_STARTUP), \
> >>> + S(SNK_DISCOVERY), \
> >>> + S(SNK_DISCOVERY_DEBOUNCE), \
> >>> + S(SNK_DISCOVERY_DEBOUNCE_DONE), \
> >>> + S(SNK_WAIT_CAPABILITIES), \
> >>> + S(SNK_NEGOTIATE_CAPABILITIES), \
> >>> + S(SNK_NEGOTIATE_PPS_CAPABILITIES), \
> >>> + S(SNK_TRANSITION_SINK), \
> >>> + S(SNK_TRANSITION_SINK_VBUS), \
> >>> + S(SNK_READY), \
> >>> + \
> >>> + S(ACC_UNATTACHED), \
> >>> + S(DEBUG_ACC_ATTACHED), \
> >>> + S(AUDIO_ACC_ATTACHED), \
> >>> + S(AUDIO_ACC_DEBOUNCE), \
> >>> + \
> >>> + S(HARD_RESET_SEND), \
> >>> + S(HARD_RESET_START), \
> >>> + S(SRC_HARD_RESET_VBUS_OFF), \
> >>> + S(SRC_HARD_RESET_VBUS_ON), \
> >>> + S(SNK_HARD_RESET_SINK_OFF), \
> >>> + S(SNK_HARD_RESET_WAIT_VBUS), \
> >>> + S(SNK_HARD_RESET_SINK_ON), \
> >>> + \
> >>> + S(SOFT_RESET), \
> >>> + S(SRC_SOFT_RESET_WAIT_SNK_TX), \
> >>> + S(SNK_SOFT_RESET), \
> >>> + S(SOFT_RESET_SEND), \
> >>> + \
> >>> + S(DR_SWAP_ACCEPT), \
> >>> + S(DR_SWAP_SEND), \
> >>> + S(DR_SWAP_SEND_TIMEOUT), \
> >>> + S(DR_SWAP_CANCEL), \
> >>> + S(DR_SWAP_CHANGE_DR), \
> >>> + \
> >>> + S(PR_SWAP_ACCEPT), \
> >>> + S(PR_SWAP_SEND), \
> >>> + S(PR_SWAP_SEND_TIMEOUT), \
> >>> + S(PR_SWAP_CANCEL), \
> >>> + S(PR_SWAP_START), \
> >>> + S(PR_SWAP_SRC_SNK_TRANSITION_OFF), \
> >>> + S(PR_SWAP_SRC_SNK_SOURCE_OFF), \
> >>> + S(PR_SWAP_SRC_SNK_SOURCE_OFF_CC_DEBOUNCED), \
> >>> + S(PR_SWAP_SRC_SNK_SINK_ON), \
> >>> + S(PR_SWAP_SNK_SRC_SINK_OFF), \
> >>> + S(PR_SWAP_SNK_SRC_SOURCE_ON), \
> >>> + S(PR_SWAP_SNK_SRC_SOURCE_ON_VBUS_RAMPED_UP), \
> >>> + \
> >>> + S(VCONN_SWAP_ACCEPT), \
> >>> + S(VCONN_SWAP_SEND), \
> >>> + S(VCONN_SWAP_SEND_TIMEOUT), \
> >>> + S(VCONN_SWAP_CANCEL), \
> >>> + S(VCONN_SWAP_START), \
> >>> + S(VCONN_SWAP_WAIT_FOR_VCONN), \
> >>> + S(VCONN_SWAP_TURN_ON_VCONN), \
> >>> + S(VCONN_SWAP_TURN_OFF_VCONN), \
> >>> + \
> >>> + S(FR_SWAP_SEND), \
> >>> + S(FR_SWAP_SEND_TIMEOUT), \
> >>> + S(FR_SWAP_SNK_SRC_TRANSITION_TO_OFF), \
> >>> + S(FR_SWAP_SNK_SRC_NEW_SINK_READY), \
> >>> + S(FR_SWAP_SNK_SRC_SOURCE_VBUS_APPLIED), \
> >>> + S(FR_SWAP_CANCEL), \
> >>> + \
> >>> + S(SNK_TRY), \
> >>> + S(SNK_TRY_WAIT), \
> >>> + S(SNK_TRY_WAIT_DEBOUNCE), \
> >>> + S(SNK_TRY_WAIT_DEBOUNCE_CHECK_VBUS), \
> >>> + S(SRC_TRYWAIT), \
> >>> + S(SRC_TRYWAIT_DEBOUNCE), \
> >>> + S(SRC_TRYWAIT_UNATTACHED), \
> >>> + \
> >>> + S(SRC_TRY), \
> >>> + S(SRC_TRY_WAIT), \
> >>> + S(SRC_TRY_DEBOUNCE), \
> >>> + S(SNK_TRYWAIT), \
> >>> + S(SNK_TRYWAIT_DEBOUNCE), \
> >>> + S(SNK_TRYWAIT_VBUS), \
> >>> + S(BIST_RX), \
> >>> + \
> >>> + S(GET_STATUS_SEND), \
> >>> + S(GET_STATUS_SEND_TIMEOUT), \
> >>> + S(GET_PPS_STATUS_SEND), \
> >>> + S(GET_PPS_STATUS_SEND_TIMEOUT), \
> >>> + \
> >>> + S(GET_SINK_CAP), \
> >>> + S(GET_SINK_CAP_TIMEOUT), \
> >>> + \
> >>> + S(ERROR_RECOVERY), \
> >>> + S(PORT_RESET), \
> >>> + S(PORT_RESET_WAIT_OFF), \
> >>> + \
> >>> + S(AMS_START), \
> >>> + S(CHUNK_NOT_SUPP)
> >>> +
> >>> +#define GENERATE_ENUM(e) e
> >>> +
> >>> +enum tcpm_state {
> >>> + FOREACH_STATE(GENERATE_ENUM)
> >>> +};
> >>> +
> >>
> >> Sorry for not bringing it up earlier; I have been struggling with it all along,
> >> and I could not decide if I should bring it up or not.
> >>
> >> I really don't feel comfortable with exporting states outside tcpm.
> >> Is this really necessary ? The only use seems to be
> >>
> >> + if ((tcpm_prev_state == SRC_ATTACH_WAIT && current_state == SRC_UNATTACHED) ||
> >> + (tcpm_prev_state == SNK_ATTACH_WAIT && current_state == SNK_UNATTACHED))
> >>
> >> Plus, of course, the CHECK_CONTAMINANT state.
> >>
> >> Is there reason to believe that the relevant state transitions would be different
> >> for other chips ? If not, would it possibly make sense to move this check
> >> into the state machine ?
> >
> > In my understanding, this is definitely one of the transitions that I
> > think will happen when the port has contaminant. It's quite possible
> > that there are transitions that I am not aware of yet.
> > I am OK moving it back to the tcpm state machine, however, then tcpm
> > would have to keep track of the tcpm state machine transitions and
> > that would look like V2 version of the patch
> > (https://lore.kernel.org/lkml/20220831001555.285081-1-badhri@xxxxxxxxxx/)
> > where disconnect_while_debouncing is used to track this. Would that be
> > OK ?
> >
>
> Kind of, except that I think it was way too invasive. The current code checks for
> contaminant once when entering the state machine. If you pull that code into the
> state machine, I don't see why it would have to be more than a single call.
> One possibility might be to move the call into tcpm_set_state() to catch all
> state transitions, or to use the existing enter_state variable for that
> purpose.

enter_state suited better ! tcpm_set_state's delayed state was making
it tricky..
So chose the enter_state path and have updated series (Version 8).
I also added a small helper function to check whether the state machine
is in toggling state.

>
> >>
> >>> enum typec_cc_status {
> >>> TYPEC_CC_OPEN,
> >>> TYPEC_CC_RA,
> >>> @@ -114,6 +234,16 @@ 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 invoked when chiplevel drivers indicated
> >>> + * that the USB port needs to be checked for contaminant presence.
> >>> + * Chip level drivers are expected to check for contaminant and call
> >>> + * tcpm_clean_port when the port is clean to put the port back into
> >>> + * toggling state.
> >>> + * @is_potential_contaminant:
> >>> + * Optional; TCPM invokes the callback for every TCPM state machine
> >>> + * transition. Chiplevel drivers can monitor the state machine
> >>> + * transitions to flag for potential contaminant presence.
> >>
> >> I kind of dislike the repeated checks for those callbacks in the state machine.
> >> Does it make any sense to have one of those callbacks but not the other ?
> >>
> >> Because if not it might make sense to check in the registration function
> >> if either both are NULL or both are set, and then drop most of the checks
> >> in the state machine handler.
> >
> > I can definitely check for the registration of the callbacks but cant
> > drop one of them unless we are OK to make tcpm transitions and invoke
> > the check_contaminant callback directly.
> >
>
> I didn't necessarily mean to drop one of the callbacks (unless one of them is
> pulled into the tcpm driver). I envisioned a check such as
> if ((!tcpc->check_contaminant && tcpc->is_potential_contaminant) ||
> ((tcpc->check_contaminant && !tcpc->is_potential_contaminant))
> return ERR_PTR(-EINVAL);
> in tcpm_register_port().
>
> With that, it would no longer be necessary to keep checking for
> port->tcpc->check_contaminant later on because potential_contaminant would only
> ever be true if the check_contaminant callback exists.

We now only have check_contaminant callback in v8 :)

>
> Another note: We currently don't log in SRC_UNATTACHED, SNK_UNATTACHED,
> and TOGGLING states. Would it make sense to add CHECK_CONTAMINANT to
> the checks in tcpm_log() ?

Sure, made the change in v8.

Thanks,
Badhri

>
> Thanks,
> Guenter
>
> > Thanks,
> > Badhri
> >
> >
> >>
> >> Thanks,
> >> Guenter
> >>
> >>> */
> >>> struct tcpc_dev {
> >>> struct fwnode_handle *fwnode;
> >>> @@ -148,6 +278,8 @@ 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);
> >>> + bool (*is_potential_contaminant)(struct tcpc_dev *dev, enum tcpm_state current_state);
> >>> };
> >>>
> >>> struct tcpm_port;
> >>> @@ -165,5 +297,6 @@ 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);
> >>>
> >>> #endif /* __LINUX_USB_TCPM_H */
> >>>
> >>> base-commit: 1524ceb14dd5ebd6f724d993c5ec1a9a8d445d8e
> >>
>

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