linux-kernel - RE: [linux-pm] [PATCH v2] [RFC] ehci: Disable wake on overcurrent (WKOC_E) and disconnect (WKDISC

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Date:	Thu, 6 May 2010 16:23:09 +0800
From:	"Du, Alek" <alek.du@...el.com>
To:	Alan Stern <stern@...land.harvard.edu>
CC:	Ondrej Zary <linux@...nbow-software.org>,
	Linux-pm mailing list <linux-pm@...ts.linux-foundation.org>,
	USB list <linux-usb@...r.kernel.org>,
	Kernel development list <linux-kernel@...r.kernel.org>
Subject: RE: [linux-pm] [PATCH v2] [RFC] ehci: Disable wake on overcurrent
 (WKOC_E) and disconnect (WKDISC_E)

>> Alan,
>>
>> As I tested, the patch breaks phy low power mode, the EHCI works, but it
>never
>> enter phy low power mode when suspending port...
>>
>> I guess this part of the diff breaks it.
>>
>>
>>  -			/* only enable appropriate wake bits, otherwise the
>>  -			 * hardware can not go phy low power mode. If a race
>>  -			 * condition happens here(connection change during bits
>>  -			 * set), the port change detection will finally fix it.
>>  -			 */
>>  -			if (t1 & PORT_CONNECT) {
>>  -				t2 |= PORT_WKOC_E | PORT_WKDISC_E;
>>  -				t2 &= ~PORT_WKCONN_E;
>>  -			} else {
>>  -				t2 |= PORT_WKOC_E | PORT_WKCONN_E;
>>  -				t2 &= ~PORT_WKDISC_E;
>>  -			}
>
>That seems very odd.  Why should removing code that enables wakeup bits
>cause the suspend to fail?  Can't the phy go into low-power mode when
>all the wakeup bits are disabled?
>
>Does applying this additional patch on top of the previous one help?
>
>Alan Stern
>
>
>
>Index: usb-2.6/drivers/usb/host/ehci-hub.c
>===================================================================
>--- usb-2.6.orig/drivers/usb/host/ehci-hub.c
>+++ usb-2.6/drivers/usb/host/ehci-hub.c
>@@ -200,7 +200,7 @@ static int ehci_bus_suspend (struct usb_
> 	while (port--) {
> 		u32 __iomem	*reg = &ehci->regs->port_status [port];
> 		u32		t1 = ehci_readl(ehci, reg) & ~PORT_RWC_BITS;
>-		u32		t2 = t1;
>+		u32		t2;
>
> 		if (ehci->has_hostpc)
> 			hostpc_reg = (u32 __iomem *)((u8 *)ehci->regs
>@@ -209,6 +209,7 @@ static int ehci_bus_suspend (struct usb_
> 		if (t1 & PORT_OWNER)
> 			set_bit(port, &ehci->owned_ports);
> 		else if ((t1 & PORT_PE) && !(t1 & PORT_SUSPEND)) {
>+			t2 = t1 & ~PORT_WAKE_BITS;
> 			t2 |= PORT_SUSPEND;
> 			set_bit(port, &ehci->bus_suspended);
> 			ehci_vdbg (ehci, "port %d, %08x -> %08x\n",


Alan,

I think the problem is: For the original code, once t2 != t1, the HCD will try to put into phy low power mode. While after the patch, the HCD will only enter phy low power mode if PORT_PE is set and PORT_SUSPEND is not set.

Thanks,
Alek

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