linux-kernel - Re: [PATCH] firewire: Fix ohci free

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Date:	Fri, 01 Feb 2013 16:14:30 -0500
From:	Peter Hurley <peter@...leysoftware.com>
To:	Mark Einon <mark.einon@...il.com>
Cc:	Alan Stern <stern@...land.harvard.edu>,
	Stefan Richter <stefanr@...6.in-berlin.de>,
	linux1394-devel@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org
Subject: Re: [PATCH] firewire: Fix ohci free_irq() warning

On Fri, 2013-02-01 at 16:09 -0500, Peter Hurley wrote:
> On Fri, 2013-02-01 at 19:13 +0000, Mark Einon wrote:
> > On 31 January 2013 15:04, Alan Stern <stern@...land.harvard.edu> wrote:
> > > On Wed, 30 Jan 2013, Mark Einon wrote:
> > >
> > >> >> > >> This patch fixes the kernel warning generated when putting an MSI MS-1727
> > >> >> > >> GT740 laptop into suspend mode. The call sequence in this case calls
> > >> >> > >> free_irq() twice, once in pci_remove() and once then in pci_suspend().
> > >> >> > >
> > >> >> > > You mean /first/ in pci_suspend() and /then/ in pci_remove() on the
> > >> >> > > already suspended devices, right?
> > >> >> >
> > >> >> > Yes, I did. The call sequence is suspend then resume. My bad.
> > >> >
> > >> > Why does the pci_suspend routine call free_irq() at all?  As far as I
> > >> > know, it's not supposed to do that.  Won't the device continue to use
> > >> > the same IRQ after it is resumed?
> > >>
> > >> This sounds reasonable to me - I think we could probably get rid of
> > >> the request_irq() call from resume, and use
> > >> disable_irq()/enable_irq()?
> > >
> > > Why mess around with IRQ settings at all?  Just have the suspend
> > > routine tell the controller to stop generating them.
> > >
> > > Alan Stern
> > >
> > 
> > I looked into doing this; using context_stop() to stop the controller running.
> > 
> > However, removing the enable_irq() from pci_resume() involves not
> > calling ohci_enable() (as it is also the fw_card_driver.enable
> > function, and can't easily be modified). As this call involves a lot
> > of register writes and I have no devices to test, I decided against
> > it.
> > 
> > I'll send an updated patch for consideration that merely uses a bool
> > to stop the irq being freed twice - crude, but it works without
> > changing too much code.

Sorry that should read...

> Hi Mark,
> 
> I think what Alan means is that the suspend/resume code should just
> mask/unmask interrupts at the OHCI controller, via the OHCI
> IntEventClear/Set registers (naturally, saving the current mask and
     ^^^^^^^^
  IntMaskClear/Set

by clearing/setting masterIntEnable

> restoring it on resume).
> 
> Of course, there's a lot more to do with an OHCI controller -- as you
> note. Like stopping running DMA contexts :)  And restarting them on
> resume.
> 
> I'd do it, but I'm buried to my eyeballs in tty right now -- not fun. I
> can _eventually_ do this as I need to address problems with the FW643
> anyway at some point, but it's going to be a little while.
> 
> In the meantime, I'm a little confused: you say you can't test this code
> because you have no hardware; but then how'd you trip this bug?
> 
> Regards,
> Peter Hurley


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