Date: Thu, 31 Oct 2024 16:59:54 -0700
In-Reply-To: <20241031235957.1261244-1-amitsd@google.com>
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Subject: [PATCH v1 3/3] usb: typec: tcpm: Add support for sink-bc12-completion-time-ms
 DT property
From: Amit Sunil Dhamne <amitsd@google.com>
To: robh@kernel.org, krzk+dt@kernel.org, conor+dt@kernel.org, 
	gregkh@linuxfoundation.org, heikki.krogerus@linux.intel.com
Cc: dmitry.baryshkov@linaro.org, kyletso@google.com, rdbabiera@google.com, 
	badhri@google.com, linux@roeck-us.net, xu.yang_2@nxp.com, 
	devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, 
	linux-usb@vger.kernel.org, Amit Sunil Dhamne <amitsd@google.com>
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Add support for parsing DT time property "sink-bc12-completion-time-ms".
This timer is used to relax the PD state machine during Sink attach to
allow completion of Battery Charging (BC1.2) charger type detection in
TCPC before PD negotiations. BC1.2 detection is a hardware mechanism to
detect charger port type that is run by some conrollers (such as
"maxim,max33359") in parallel to Type-C connection state machines.
This is to ensure that BC1.2 completes before PD is enabled as running
BC1.2 in parallel with PD negotiation results in delays violating timer
constraints in PD spec.

This is an optional timer and will not add any delay unless explicitly
set.

Signed-off-by: Amit Sunil Dhamne <amitsd@google.com>
Reviewed-by: Badhri Jagan Sridharan <badhri@google.com>
---
 drivers/usb/typec/tcpm/tcpm.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
index b3d5d1d48937..8b325b93b5a9 100644
--- a/drivers/usb/typec/tcpm/tcpm.c
+++ b/drivers/usb/typec/tcpm/tcpm.c
@@ -319,6 +319,7 @@ struct pd_timings {
 	u32 sink_wait_cap_time;
 	u32 ps_src_off_time;
 	u32 cc_debounce_time;
+	u32 snk_bc12_cmpletion_time;
 };
 
 struct tcpm_port {
@@ -4978,7 +4979,16 @@ static void run_state_machine(struct tcpm_port *port)
 		if (ret < 0)
 			tcpm_set_state(port, SNK_UNATTACHED, 0);
 		else
-			tcpm_set_state(port, SNK_STARTUP, 0);
+			/*
+			 * For Type C port controllers that use Battery Charging
+			 * Detection (based on BCv1.2 spec) to detect USB
+			 * charger type, add a delay of "snk_bc12_cmpletion_time"
+			 * before transitioning to SNK_STARTUP to allow BC1.2
+			 * detection to complete before PD is eventually enabled
+			 * in later states.
+			 */
+			tcpm_set_state(port, SNK_STARTUP,
+				       port->timings.snk_bc12_cmpletion_time);
 		break;
 	case SNK_STARTUP:
 		opmode =  tcpm_get_pwr_opmode(port->polarity ?
@@ -7090,6 +7100,10 @@ static void tcpm_fw_get_timings(struct tcpm_port *port, struct fwnode_handle *fw
 		port->timings.cc_debounce_time = val;
 	else
 		port->timings.cc_debounce_time = PD_T_CC_DEBOUNCE;
+
+	ret = fwnode_property_read_u32(fwnode, "sink-bc12-completion-time-ms", &val);
+	if (!ret)
+		port->timings.snk_bc12_cmpletion_time = val;
 }
 
 static int tcpm_fw_get_caps(struct tcpm_port *port, struct fwnode_handle *fwnode)
-- 
2.47.0.199.ga7371fff76-goog