linux-kernel - Re: [PATCH 07/10] ehci-dbgp,ehci: Allow early or late use of the dbgp device

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Date:	Sat, 1 Aug 2009 11:47:24 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Jason Wessel <jason.wessel@...driver.com>
cc:	gregkh@...e.de, <linux-usb@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <dbrownell@...rs.sourceforge.net>,
	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Yinghai Lu <yinghai@...nel.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>
Subject: Re: [PATCH 07/10] ehci-dbgp,ehci: Allow early or late use of the
 dbgp device

On Fri, 31 Jul 2009, Jason Wessel wrote:

> Alan Stern wrote:
> > What happens across a system suspend?
> >
> >   
> 
> I assume you mean as a test case:
> 
> echo -n mem > /sys/power/state
> 
> The dbgp device goes away entirely, when used with
> earlyprintk=dbgp,keep.  But there is a way to fix it reasonably
> easily.  Perhaps you might ack this resume patch, if you agree?
> 
> Jason.
> 
> ---
> From: Jason Wessel <jason.wessel@...driver.com>
> Subject: [PATCH] ehci-dbgp,ehci: Allow dbpg to work with suspend/resume
> 
> In order for the dbgp driver to survive suspend/resume, on every ehci
> resume operation the debug controller must get re-initialized.
> 
> Signed-off-by: Jason Wessel <jason.wessel@...driver.com>
> Cc: Greg KH <gregkh@...e.de>
> Cc: Alan Stern <stern@...land.harvard.edu>
> Cc: dbrownell@...rs.sourceforge.net
> Cc: Ingo Molnar <mingo@...e.hu>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Yinghai Lu <yinghai@...nel.org>
> Cc: "Eric W. Biederman" <ebiederm@...ssion.com>
> 
> ---
>  drivers/usb/host/ehci-hub.c |    6 ++++++
>  1 file changed, 6 insertions(+)
> 
> --- a/drivers/usb/host/ehci-hub.c
> +++ b/drivers/usb/host/ehci-hub.c
> @@ -204,6 +204,13 @@ static int ehci_bus_resume (struct usb_h
>  		return -ESHUTDOWN;
>  	}
>  
> +	if (unlikely(ehci->debug)) {
> +		if (ehci->debug && !dbgp_reset_prep())
> +			ehci->debug = NULL;
> +		else
> +			dbgp_external_startup();
> +	}
> +
>  	/* Ideally and we've got a real resume here, and no port's power
>  	 * was lost.  (For PCI, that means Vaux was maintained.)  But we
>  	 * could instead be restoring a swsusp snapshot -- so that BIOS was

It looks fine to me.  Would you perhaps want to make dbgp_reset_prep()
automatically call dbgp_external_startup() on success so that ehci-hcd
doesn't have to?

Alan Stern

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