linux-kernel - [PATCH v2] usb: hub: Clear Port Reset Change during init/resume

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Date:	Tue, 15 Oct 2013 17:45:00 -0700
From:	Julius Werner <jwerner@...omium.org>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
	Alan Stern <stern@...land.harvard.edu>,
	Sarah Sharp <sarah.a.sharp@...ux.intel.com>,
	Benson Leung <bleung@...omium.org>,
	Vincent Palatin <vpalatin@...omium.org>,
	Duncan Laurie <dlaurie@...omium.org>,
	Julius Werner <jwerner@...omium.org>
Subject: [PATCH v2] usb: hub: Clear Port Reset Change during init/resume

This patch adds the Port Reset Change flag to the set of bits that are
preemptively cleared on init/resume of a hub. In theory this bit should
never be set unexpectedly... in practice it can still happen if BIOS,
SMM or ACPI code plays around with USB devices without cleaning up
correctly. This is especially dangerous for XHCI root hubs, which don't
generate any more Port Status Change Events until all change bits are
cleared, so this is a good precaution to have (similar to how it's
already done for the Warm Port Reset Change flag).

Signed-off-by: Julius Werner <jwerner@...omium.org>
---
 drivers/usb/core/hub.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index e6b682c..c3dd64c 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -1130,6 +1130,11 @@ static void hub_activate(struct usb_hub *hub, enum hub_activation_type type)
 			usb_clear_port_feature(hub->hdev, port1,
 					USB_PORT_FEAT_C_ENABLE);
 		}
+		if (portchange & USB_PORT_STAT_C_RESET) {
+			need_debounce_delay = true;
+			usb_clear_port_feature(hub->hdev, port1,
+					USB_PORT_FEAT_C_RESET);
+		}
 		if ((portchange & USB_PORT_STAT_C_BH_RESET) &&
 				hub_is_superspeed(hub->hdev)) {
 			need_debounce_delay = true;
-- 
1.7.12.4

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