[PATCH 4.19 110/190] usb: typec: tcpm: Try PD-2.0 if sink does not respond to 3.0 source-caps

Greg Kroah-Hartman
2019-09-13T13:16:30Z

[ Upstream commit 976daf9d1199932df80e7b04546d1a1bd4ed5ece ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/usb/typec/tcpm.c | 27 ++++++++++++++++++++++++++-
1 file changed, 26 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/typec/tcpm.c b/drivers/usb/typec/tcpm.c
index fb20aa974ae12..819ae3b2bd7e8 100644
--- a/drivers/usb/typec/tcpm.c
+++ b/drivers/usb/typec/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), \
@@ -2987,10 +2988,34 @@ static void run_state_machine(struct tcpm_port *port)
/* 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) {
--
2.20.1