patch "usb: core: hub: Improved device recognition on remote wakeup" added to usb-linus

This is a note to let you know that I've just added the patch titled

usb: core: hub: Improved device recognition on remote wakeup

to my usb git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git
in the usb-linus branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.

If you have any questions about this process, please let me know.

From 9c06ac4c83df6d6fbdbf7488fbad822b4002ba19 Mon Sep 17 00:00:00 2001
From: Keiya Nobuta <[email protected]>
Date: Thu, 9 Jan 2020 14:14:48 +0900
Subject: usb: core: hub: Improved device recognition on remote wakeup

If hub_activate() is called before D+ has stabilized after remote wakeup, the following situation might occur:

         __      ___________________
        /  \    /

D+ __/ \__/

Hub _______________________________

          |  ^   ^           ^
          |  |   |           |
Host _____v__|___|___________|______
          |  |   |           |
          |  |   |           \-- Interrupt Transfer (*3)
          |  |    \-- ClearPortFeature (*2)

| \-- GetPortStatus (*1)
\-- Host detects remote wakeup

- D+ goes high, Host starts running by remote wakeup
- D+ is not stable, goes low
- Host requests GetPortStatus at (*1) and gets the following hub status:
- Current Connect Status bit is 0
- Connect Status Change bit is 1
- D+ stabilizes, goes high
- Host requests ClearPortFeature and thus Connect Status Change bit is cleared at (*2)
- After waiting 100 ms, Host starts the Interrupt Transfer at (*3)
- Since the Connect Status Change bit is 0, Hub returns NAK.

In this case, port_event() is not called in hub_event() and Host cannot recognize device. To solve this issue, flag change_bits even if only Connect Status Change bit is 1 when got in the first GetPortStatus.

This issue occurs rarely because it only if D+ changes during a very short time between GetPortStatus and ClearPortFeature. However, it is fatal if it occurs in embedded system.

---
 drivers/usb/core/hub.c | 1 +
 1 file changed, 1 insertion(+)

index 8c4e5adbf820..3405b146edc9 100644
@@ -1192,6 +1192,7 @@ static void hub_activate(struct usb_hub *hub, enum hub_activation_type type)
 			 * PORT_OVER_CURRENT is not. So check for any of them.
 			 */
 			if (udev || (portstatus & USB_PORT_STAT_CONNECTION) ||
+			    (portchange & USB_PORT_STAT_C_CONNECTION) ||
 			    (portstatus & USB_PORT_STAT_OVERCURRENT) ||
 			    (portchange & USB_PORT_STAT_C_OVERCURRENT))
 				set_bit(port1, hub->change_bits);

2.24.1