linux-kernel - [PATCH v1] tcpm: Avoid soft reset when partner does not support get

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Date:   Sun, 20 Aug 2023 04:44:48 +0000
From:   Badhri Jagan Sridharan <badhri@...gle.com>
To:     gregkh@...uxfoundation.org, linux@...ck-us.net,
        heikki.krogerus@...ux.intel.com
Cc:     kyletso@...gle.com, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Badhri Jagan Sridharan <badhri@...gle.com>
Subject: [PATCH v1] tcpm: Avoid soft reset when partner does not support get_status

When partner does not support get_status message, tcpm right now
responds with soft reset message. This causes PD renegotiation to
happen and resets PPS link. Avoid soft resetting the link when
partner does not support get_status message to mitigate PPS resets.

[  208.926752] Setting voltage/current limit 9500 mV 2450 mA
[  208.930407] set_auto_vbus_discharge_threshold mode:3 pps_active:y vbus:9500 ret:0
[  208.930418] state change SNK_TRANSITION_SINK -> SNK_READY [rev3 POWER_NEGOTIATION]
[  208.930455] AMS POWER_NEGOTIATION finished

// ALERT message from the Source
[  213.948442] PD RX, header: 0x19a6 [1]
[  213.948451] state change SNK_READY -> GET_STATUS_SEND [rev3 GETTING_SOURCE_SINK_STATUS]
[  213.948457] PD TX, header: 0x492
[  213.950402] PD TX complete, status: 0
[  213.950427] pending state change GET_STATUS_SEND -> GET_STATUS_SEND_TIMEOUT @ 60 ms [rev3 GETTING_SOURCE_SINK_STATUS]

// NOT_SUPPORTED from the Source
[  213.959954] PD RX, header: 0xbb0 [1]

// sink sends SOFT_RESET
[  213.959958] state change GET_STATUS_SEND -> SNK_SOFT_RESET [rev3 GETTING_SOURCE_SINK_STATUS]
[  213.959962] AMS GETTING_SOURCE_SINK_STATUS finished
[  213.959964] AMS SOFT_RESET_AMS start
[  213.959966] state change SNK_SOFT_RESET -> AMS_START [rev3 SOFT_RESET_AMS]
[  213.959969] state change AMS_START -> SOFT_RESET_SEND [rev3 SOFT_RESET_AMS]

Cc: stable@...r.kernel.org
Fixes: 8dea75e11380 ("usb: typec: tcpm: Protocol Error handling")
Signed-off-by: Badhri Jagan Sridharan <badhri@...gle.com>
---
 drivers/usb/typec/tcpm/tcpm.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
index 5639b9a1e0bf..280ce1bd7b53 100644
--- a/drivers/usb/typec/tcpm/tcpm.c
+++ b/drivers/usb/typec/tcpm/tcpm.c
@@ -2753,6 +2753,13 @@ static void tcpm_pd_ctrl_request(struct tcpm_port *port,
 			port->sink_cap_done = true;
 			tcpm_set_state(port, ready_state(port), 0);
 			break;
+		/*
+		 * Some port partners do not support GET_STATUS, avoid soft reset the link to
+		 * prevent redundant power re-negotiation
+		 */
+		case GET_STATUS_SEND:
+			tcpm_set_state(port, ready_state(port), 0);
+			break;
 		case SRC_READY:
 		case SNK_READY:
 			if (port->vdm_state > VDM_STATE_READY) {

base-commit: bbb9e06d2c6435af9c62074ad7048910eeb2e7bc
-- 
2.42.0.rc1.204.g551eb34607-goog