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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Hans de Goede <hdegoede@redhat.com>,
        Guenter Roeck <linux@roeck-us.net>
Subject: [PATCH 5.0 123/146] usb: typec: tcpm: Try PD-2.0 if sink does not respond to 3.0 source-caps
Date:   Mon,  1 Apr 2019 19:02:15 +0200
Message-Id: <20190401170058.723014657@linuxfoundation.org>
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5.0-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Hans de Goede <hdegoede@redhat.com>

commit 976daf9d1199932df80e7b04546d1a1bd4ed5ece upstream.

PD 2.0 sinks are supposed to accept src-capabilities with a 3.0 header and
simply ignore any src PDOs which the sink does not understand such as PPS
but some 2.0 sinks instead ignore the entire PD_DATA_SOURCE_CAP message,
causing contract negotiation to fail.

This commit fixes such sinks not working by re-trying the contract
negotiation with PD-2.0 source-caps messages if we don't have a contract
after PD_N_HARD_RESET_COUNT hard-reset attempts.

The problem fixed by this commit was noticed with a Type-C to VGA dongle.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/usb/typec/tcpm/tcpm.c |   27 ++++++++++++++++++++++++++-
 1 file changed, 26 insertions(+), 1 deletion(-)

--- a/drivers/usb/typec/tcpm/tcpm.c
+++ b/drivers/usb/typec/tcpm/tcpm.c
@@ -37,6 +37,7 @@
 	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),				\
@@ -2966,10 +2967,34 @@ static void run_state_machine(struct tcp
 			/* port->hard_reset_count = 0; */
 			port->caps_count = 0;
 			port->pd_capable = true;
-			tcpm_set_state_cond(port, hard_reset_state(port),
+			tcpm_set_state_cond(port, SRC_SEND_CAPABILITIES_TIMEOUT,
 					    PD_T_SEND_SOURCE_CAP);
 		}
 		break;
+	case SRC_SEND_CAPABILITIES_TIMEOUT:
+		/*
+		 * Error recovery for a PD_DATA_SOURCE_CAP reply timeout.
+		 *
+		 * PD 2.0 sinks are supposed to accept src-capabilities with a
+		 * 3.0 header and simply ignore any src PDOs which the sink does
+		 * not understand such as PPS but some 2.0 sinks instead ignore
+		 * the entire PD_DATA_SOURCE_CAP message, causing contract
+		 * negotiation to fail.
+		 *
+		 * After PD_N_HARD_RESET_COUNT hard-reset attempts, we try
+		 * sending src-capabilities with a lower PD revision to
+		 * make these broken sinks work.
+		 */
+		if (port->hard_reset_count < PD_N_HARD_RESET_COUNT) {
+			tcpm_set_state(port, HARD_RESET_SEND, 0);
+		} else if (port->negotiated_rev > PD_REV20) {
+			port->negotiated_rev--;
+			port->hard_reset_count = 0;
+			tcpm_set_state(port, SRC_SEND_CAPABILITIES, 0);
+		} else {
+			tcpm_set_state(port, hard_reset_state(port), 0);
+		}
+		break;
 	case SRC_NEGOTIATE_CAPABILITIES:
 		ret = tcpm_pd_check_request(port);
 		if (ret < 0) {