[34-longterm 137/179] EHCI: only power off port if over-current is active

From: Paul Gortmaker
Date: Mon May 14 2012 - 22:37:44 EST

From: Sergei Shtylyov <sshtylyov@xxxxxxxxxxxxx>

This is a commit scheduled for the next v2.6.34 longterm release.
If you see a problem with using this for longterm, please comment.

commit 81463c1d707186adbbe534016cd1249edeab0dac upstream.

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@xxxxxxxxxxxxx>
Acked-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>
Signed-off-by: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>
drivers/usb/host/ehci-hub.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/host/ehci-hub.c b/drivers/usb/host/ehci-hub.c
index 1b2af4d..ae32f02 100644
--- a/drivers/usb/host/ehci-hub.c
+++ b/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)) {
+ temp = ehci_readl(ehci, status_reg);


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