linux-kernel - [PATCH 4.4 032/113] usb: ehci: change order of register cleanup during shutdown

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Date:   Mon,  5 Sep 2016 18:43:55 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Marc Ohlf <ohlf@...-sys.de>,
        Alan Stern <stern@...land.harvard.edu>
Subject: [PATCH 4.4 032/113] usb: ehci: change order of register cleanup during shutdown

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Marc Ohlf <ohlf@...-sys.de>

commit bc337b51508beb2d039aff5074a76cfe1c212030 upstream.

In ehci_turn_off_all_ports() all EHCI port registers are cleared to zero.
On some hardware, this can lead to an system hang,
when ehci_port_power() accesses the already cleared registers.

This patch changes the order of cleanup.
First call ehci_port_power() which respects the current bits in
port status registers
and afterwards cleanup the hard way by setting everything to zero.

Signed-off-by: Marc Ohlf <ohlf@...-sys.de>
Acked-by: Alan Stern <stern@...land.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/usb/host/ehci-hcd.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/usb/host/ehci-hcd.c
+++ b/drivers/usb/host/ehci-hcd.c
@@ -332,11 +332,11 @@ static void ehci_turn_off_all_ports(stru
 	int	port = HCS_N_PORTS(ehci->hcs_params);
 
 	while (port--) {
-		ehci_writel(ehci, PORT_RWC_BITS,
-				&ehci->regs->port_status[port]);
 		spin_unlock_irq(&ehci->lock);
 		ehci_port_power(ehci, port, false);
 		spin_lock_irq(&ehci->lock);
+		ehci_writel(ehci, PORT_RWC_BITS,
+				&ehci->regs->port_status[port]);
 	}
 }