linux-kernel - [PATCH 1/2] typec: tcpm: Do not disconnect link for self powered devices

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Date:   Wed, 12 Sep 2018 19:11:12 -0700
From:   Badhri Jagan Sridharan <badhri@...gle.com>
To:     Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        Badhri Jagan Sridharan <badhri@...gle.com>,
        Badhri Jagan Sridharan <Badhri@...gle.com>
Subject: [PATCH 1/2] typec: tcpm: Do not disconnect link for self powered devices

During HARD_RESET the data link is disconnected.
For self powered device, the spec is advising against doing that.

>From USB_PD_R3_0
7.1.5 Response to Hard Resets
Device operation during and after a Hard Reset is defined as follows:
Self-powered devices Should Not disconnect from USB during a Hard Reset
(see Section 9.1.2).
Bus powered devices will disconnect from USB during a Hard Reset due to the
loss of their power source.

Tackle this by letting TCPM know whether the device is self or bus powered.

This overcomes unnecessary port disconnections from hard reset.
Also, speeds up the enumeration time when connected to Type-A ports.

Signed-off-by: Badhri Jagan Sridharan <Badhri@...gle.com>
---
 drivers/usb/typec/tcpm.c | 6 +++++-
 include/linux/usb/tcpm.h | 1 +
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/typec/tcpm.c b/drivers/usb/typec/tcpm.c
index 4f1f4215f3d6..a4e0c027a2a9 100644
--- a/drivers/usb/typec/tcpm.c
+++ b/drivers/usb/typec/tcpm.c
@@ -3270,7 +3270,11 @@ static void run_state_machine(struct tcpm_port *port)
 		memset(&port->pps_data, 0, sizeof(port->pps_data));
 		tcpm_set_vconn(port, false);
 		tcpm_set_charge(port, false);
-		tcpm_set_roles(port, false, TYPEC_SINK, TYPEC_DEVICE);
+
+		if (port->tcpc->config->self_powered)
+			tcpm_set_roles(port, true, TYPEC_SINK, TYPEC_DEVICE);
+		else
+			tcpm_set_roles(port, false, TYPEC_SINK, TYPEC_DEVICE);
 		/*
 		 * VBUS may or may not toggle, depending on the adapter.
 		 * If it doesn't toggle, transition to SNK_HARD_RESET_SINK_ON
diff --git a/include/linux/usb/tcpm.h b/include/linux/usb/tcpm.h
index 7e7fbfb84e8e..50c74a77db55 100644
--- a/include/linux/usb/tcpm.h
+++ b/include/linux/usb/tcpm.h
@@ -89,6 +89,7 @@ struct tcpc_config {
 	enum typec_port_data data;
 	enum typec_role default_role;
 	bool try_role_hw;	/* try.{src,snk} implemented in hardware */
+	bool self_powered;	/* port belongs to a self powered device */
 
 	const struct typec_altmode_desc *alt_modes;
 };
-- 
2.19.0.397.gdd90340f6a-goog