Message-Id: <201010132348.17485.rjw@sisk.pl>
Date:	Wed, 13 Oct 2010 23:48:17 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Jesse Barnes <jbarnes@...tuousgeek.org>
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 Wednesday, October 13, 2010, Jesse Barnes wrote:
> 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.
> 
> Here's what I had in mind.  I think it's safer than setting the power
> state at enable time, and it works around the enable_cnt leak in the
> DRM drivers.

However, it would have to be done after pci_pm_init() runs.  Perhaps we can
make pci_pm_init() itself put the device into D0?

Thanks,
Rafael
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