On Tue, 12 Oct 2010 12:49:38 -0700
Jesse Barnes <[email protected]> wrote:
> On Tue, 12 Oct 2010 21:01:17 +0200
> "Rafael J. Wysocki" <[email protected]> wrote:
>
> > On Tuesday, October 12, 2010, Jesse Barnes wrote:
> > > On Mon, 11 Oct 2010 15:48:26 -0700
> > > Jesse Barnes <[email protected]> wrote:
> > >
> > > > On Fri, 8 Oct 2010 21:46:50 +1000
> > > > Dave Airlie <[email protected]> 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?
>
does this need to go to 2.6.36.y? (is it already on it's way?)
commit 97c145f7c87453cec90e91238fba5fe2c1561b32
Author: Jesse Barnes <[email protected]>
Date: Fri Nov 5 15:16:36 2010 -0400
PCI: read current power state at enable time
On Tue, 16 Nov 2010 20:46:45 +0100
Florian Mickler <[email protected]> wrote:
> On Tue, 12 Oct 2010 12:49:38 -0700
> Jesse Barnes <[email protected]> wrote:
> > 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?
> >
>
> does this need to go to 2.6.36.y? (is it already on it's way?)
>
> commit 97c145f7c87453cec90e91238fba5fe2c1561b32
> Author: Jesse Barnes <[email protected]>
> Date: Fri Nov 5 15:16:36 2010 -0400
>
> PCI: read current power state at enable time
I hadn't planned on pushing this to stable, but if you have a need
for it there, feel free to propose it.
--
Jesse Barnes, Intel Open Source Technology Center
On Tue, 16 Nov 2010 12:11:07 -0800
Jesse Barnes <[email protected]> wrote:
> On Tue, 16 Nov 2010 20:46:45 +0100
> Florian Mickler <[email protected]> wrote:
>
> > On Tue, 12 Oct 2010 12:49:38 -0700
> > Jesse Barnes <[email protected]> wrote:
> > > 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?
> > >
> >
> > does this need to go to 2.6.36.y? (is it already on it's way?)
> >
> > commit 97c145f7c87453cec90e91238fba5fe2c1561b32
> > Author: Jesse Barnes <[email protected]>
> > Date: Fri Nov 5 15:16:36 2010 -0400
> >
> > PCI: read current power state at enable time
>
> I hadn't planned on pushing this to stable, but if you have a need
> for it there, feel free to propose it.
>
No, I don't need it. I was closing a regression tracker and thought I
should check. You can judge the impact better then me.
Regards,
Flo