linux-kernel - [PATCH] [30/50] EHCI: only power off port if over-current is active

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Date:	Thu, 28 Jul 2011 16:44:34 -0700 (PDT)
From:	Andi Kleen <andi@...stfloor.org>
To:	sshtylyov@...mvista.com, stern@...land.harvard.edu, gregkh@...e.de,
	ak@...ux.intel.com, linux-kernel@...r.kernel.org,
	stable@...nel.org, tim.bird@...sony.com
Subject: [PATCH] [30/50] EHCI: only power off port if over-current is active

2.6.35-longterm review patch.  If anyone has any objections, please let me know.

------------------
From: Sergei Shtylyov <sshtylyov@...mvista.com>

[ upstream commit 81463c1d707186adbbe534016cd1249edeab0dac ]

MAX4967 USB power supply chip we use on our boards signals over-current when
power is not enabled; once it's enabled, over-current signal returns to normal.
That unfortunately caused the endless stream of "over-current change on port"
messages. The EHCI root hub code reacts on every over-current signal change
with powering off the port -- such change event is generated the moment the
port power is enabled, so once enabled the power is immediately cut off.
I think we should only cut off power when we're seeing the active over-current
signal, so I'm adding such check to that code. I also think that the fact that
we've cut off the port power should be reflected in the result of GetPortStatus
request immediately, hence I'm adding a PORTSCn register readback after write...

Signed-off-by: Sergei Shtylyov <sshtylyov@...mvista.com>
Cc: stable@...nel.org
Acked-by: Alan Stern <stern@...land.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>
Signed-off-by: Andi Kleen <ak@...ux.intel.com>

Index: linux-2.6.35.y/drivers/usb/host/ehci-hub.c
===================================================================
--- linux-2.6.35.y.orig/drivers/usb/host/ehci-hub.c
+++ linux-2.6.35.y/drivers/usb/host/ehci-hub.c
@@ -837,10 +837,11 @@ static int ehci_hub_control (
 			 * power switching; they're allowed to just limit the
 			 * current.  khubd will turn the power back on.
 			 */
-			if (HCS_PPC (ehci->hcs_params)){
+			if ((temp & PORT_OC) && HCS_PPC(ehci->hcs_params)) {
 				ehci_writel(ehci,
 					temp & ~(PORT_RWC_BITS | PORT_POWER),
 					status_reg);
+				temp = ehci_readl(ehci, status_reg);
 			}
 		}

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