Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Sender: Guenter Roeck <groeck7@gmail.com>
Message-ID: <0aa7cc2e-aabd-dde0-db83-81f9627f5c54@roeck-us.net>
Date:   Thu, 12 Jan 2023 06:55:05 -0800
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101
 Thunderbird/102.4.2
Subject: Re: [PATCH v11 1/3] usb: typec: tcpm: Add callbacks to mitigate
 wakeups due to contaminant
Content-Language: en-US
To:     Heikki Krogerus <heikki.krogerus@linux.intel.com>,
        Badhri Jagan Sridharan <badhri@google.com>
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org,
        Kyle Tso <kyletso@google.com>
References: <20221223102122.1038499-1-badhri@google.com>
 <Y8AQuB//ZV3VrPJz@kuha.fi.intel.com>
From:   Guenter Roeck <linux@roeck-us.net>
In-Reply-To: <Y8AQuB//ZV3VrPJz@kuha.fi.intel.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Precedence: bulk

On 1/12/23 05:52, Heikki Krogerus wrote:
> On Fri, Dec 23, 2022 at 02:21:20AM -0800, 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@google.com>
> 
> Guenter should take a look at this. I don't have any better ideas or
> comments. For the whole series:
> 

Sorry, series got lost from my inbox. I just sent feedback. Only
concern I have is error handling (or lack of it) in patch 3/3.

Guenter

> Acked-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
> 
>> ---
>> Changes since v10:
>> * Fall back to default state if enabling toggling fails when
>> * exiting CHECK_CONTAMINANT state
>> Changes since v9:
>> * Invoke tcpm_start_toggling before transitioning to TOGGLING from
>> * CHECK_CONTAMINANT.
>> 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 | 55 ++++++++++++++++++++++++++++++++++-
>>   include/linux/usb/tcpm.h      |  8 +++++
>>   2 files changed, 62 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
>> index 904c7b4ce2f0..c624747f32df 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 +5454,15 @@ 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) {
>> +				if (tcpm_start_toggling(port, tcpm_rp_cc(port)))
>> +					tcpm_set_state(port, TOGGLING, 0);
>> +				else
>> +					tcpm_set_state(port, tcpm_default_state(port), 0);
>> +			}
>> +		}
>>   
>>   		spin_lock(&port->pd_event_lock);
>>   	}
>> @@ -5477,6 +5515,21 @@ 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: 6feb57c2fd7c787aecf2846a535248899e7b70fa
>> -- 
>> 2.39.0.314.g84b9a713c41-goog
>