linux-kernel - [PATCH v2] usb: hub: Cycle HUB power when initialization fails

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Message-Id: <Pine.LNX.4.44L0.1711031320290.1743-100000@iolanthe.rowland.org>
Date:   Thu,  9 Nov 2017 13:16:46 +0100
From:   Mike Looijmans <mike.looijmans@...ic.nl>
To:     linux-usb@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, gregkh@...uxfoundation.org,
        stern@...land.harvard.edu, linux@...ck-us.net,
        Mike Looijmans <mike.looijmans@...ic.nl>
Subject: [PATCH v2] usb: hub: Cycle HUB power when initialization fails

Sometimes the USB device gets confused about the state of the initialization and
the connection fails. In particular, the device thinks that it's already set up
and running while the host thinks the device still needs to be configured. To
work around this issue, power-cycle the hub's output to issue a sort of "reset"
to the device. This makes the device restart its state machine and then the
initialization succeeds.

This fixes problems where the kernel reports a list of errors like this:

usb 1-1.3: device not accepting address 19, error -71

The end result is a non-functioning device. After this patch, the sequence
becomes like this:

usb 1-1.3: new high-speed USB device number 18 using ci_hdrc
usb 1-1.3: device not accepting address 18, error -71
usb 1-1.3: new high-speed USB device number 19 using ci_hdrc
usb 1-1.3: device not accepting address 19, error -71
usb 1-1-port3: attempt power cycle
usb 1-1.3: new high-speed USB device number 21 using ci_hdrc
usb-storage 1-1.3:1.2: USB Mass Storage device detected

Signed-off-by: Mike Looijmans <mike.looijmans@...ic.nl>
---
v2: On feedback from Alan Stern:
      No blank line changes
      Don't further increase the retry count
    Delay 2x the power-up delay (100ms minimum) instead of magic "800"

 drivers/usb/core/hub.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index e9ce6bb..8f7d942 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -4935,6 +4935,15 @@ static void hub_port_connect(struct usb_hub *hub, int port1, u16 portstatus,
 		usb_put_dev(udev);
 		if ((status == -ENOTCONN) || (status == -ENOTSUPP))
 			break;
+
+		/* When halfway through our retry count, power-cycle the port */
+		if (i == (SET_CONFIG_TRIES / 2) - 1) {
+			dev_info(&port_dev->dev, "attempt power cycle\n");
+			usb_hub_set_port_power(hdev, hub, port1, false);
+			msleep(2 * hub_power_on_good_delay(hub));
+			usb_hub_set_port_power(hdev, hub, port1, true);
+			msleep(hub_power_on_good_delay(hub));
+		}
 	}
 	if (hub->hdev->parent ||
 			!hcd->driver->port_handed_over ||
-- 
1.9.1