linux-kernel - Re: "do_IRQ: 0.89 No irq handler for vector (irq -1)"

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Message-ID: <20101012124938.47170457@jbarnes-desktop>
Date:	Tue, 12 Oct 2010 12:49:38 -0700
From:	Jesse Barnes <jbarnes@...tuousgeek.org>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Dave Airlie <airlied@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
	Keith Packard <keithp@...thp.com>
Subject: Re: "do_IRQ: 0.89 No irq handler for vector (irq -1)"

On Tue, 12 Oct 2010 21:01:17 +0200
"Rafael J. Wysocki" <rjw@...k.pl> wrote:

> On Tuesday, October 12, 2010, Jesse Barnes wrote:
> > On Mon, 11 Oct 2010 15:48:26 -0700
> > Jesse Barnes <jbarnes@...tuousgeek.org> wrote:
> > 
> > > On Fri, 8 Oct 2010 21:46:50 +1000
> > > Dave Airlie <airlied@...il.com> wrote:
> > > > Not sure how best to fix, I can workaround by calling
> > > > pci_set_power_state(PCI_D0) in the drm drivers, but I sorta thing the
> > > > PCI layer should take care of this.
> > > 
> > > So I think we *should* be able to call pci_disable_device at remove
> > > time.  But as you say, some platforms may not correctly re-route VGA
> > > space to an existing device or disable it properly when we do that.
> > > AFAICT x86 will be ok here though (seems to work ok locally too).
> > 
> > Just tested this some more, and I think it's the right thing to do in
> > the KMS case at least.  When we load a KMS driver it takes over the gfx
> > device and nothing can assume anything about VGA state unless using the
> > VGA arbiter.  So calling pci_disable_device() in the shutdown path of a
> > KMS driver shouldn't make things any worse, and will work around this
> > issue.
> > 
> > Doing so in the non-KMS case violates some PC assumptions though, in
> > that things like vgacon and the BIOS will assume VGA memory is still
> > around, which on some platforms pci_disable_device() may affect (I only
> > checked the x86 implementation).
> > 
> > > That said, it seems like we should update the current device state at
> > > load time as well, once we've matched the driver it seems like there
> > > should be no harm.
> > > 
> > > Rafael, what do you think?  Would having the correct power state at
> > > load time cause any trouble with other PM code?  I know we've had
> > > issues with setting it explicitly in the past...
> > 
> > So we should probably make pci_enable_device pick up the current state
> > as well, instead of assuming it's unknown just because the enable count
> > was non-zero (which as Dave points out, can be affected by sysfs writes
> > too).
> > 
> > The only downside I can think of there is that if the device is already
> > enabled, we generally have to assume another driver owns it, and who
> > knows if the device is actually alive enough to read the current state
> > from.  But I think we handle those errors ok too, so pulling it out
> > should be safe.
> 
> I remember trying to do something like this and it didn't play well with the
> initialization.  Still, I didn't do that in pci_enable_device(), so I can't say
> for sure at the moment.  I _think_ it will be fine, though.

Seems to work ok for the buggy i915 reload case.  But looking at it
again, I really don't like two things:
  1) doing just the set_power_state seems wrong, what about the rest of
  enable?
  2) allowing nested enables at all

I know sysfs currently allows us to bump the enable count to arbitrary
levels, but that's easy to fix; we can just check pci_is_enabled()
before calling enable_device in the sysfs store routine.

If we did that, we could warn when pci_enable_device is called in a
nested way, which is generally a bug (two drivers trying to take over a
device?).

I don't think I buy that VGA is special anyway, at least not for KMS
enabled kernels, where vgacon and the BIOS can't assume anything about
graphics state anymore.  More generally, I don't think BIOSes have been
able to assume anything about the current graphics state since Windows
3.1, when most platforms stopped using BIOS calls and/or VGA regs for
mode setting.

Thoughts?

-- 
Jesse Barnes, Intel Open Source Technology Center

--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -963,9 +963,6 @@ static int do_pci_enable_device(struct pci_dev *dev, int bar
 {
        int err;
 
-       err = pci_set_power_state(dev, PCI_D0);
-       if (err < 0 && err != -EIO)
-               return err;
        err = pcibios_enable_device(dev, bars);
        if (err < 0)
                return err;
@@ -994,6 +991,10 @@ static int __pci_enable_device_flags(struct pci_dev *dev,
        int err;
        int i, bars = 0;
 
+       err = pci_set_power_state(dev, PCI_D0);
+       if (err < 0 && err != -EIO)
+               return err;
+
        if (atomic_add_return(1, &dev->enable_cnt) > 1)
                return 0;               /* already enabled */
 
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