Re: [Intel-gfx] [PATCH] drm/i915: fix failure to power off after hibernate

[Imre Deak <imre.deak@intel.com>]

On Fri, 2015-02-27 at 14:15 +0200, David Weinehall wrote:
> On Thu, Feb 26, 2015 at 09:01:27PM +0100, Daniel Vetter wrote:
> > On Thu, Feb 26, 2015 at 08:50:48PM +0200, Imre Deak wrote:
> 
> [snip]
> > > 
> > > The problem seems to be that after the kernel puts the device into D3
> > > the BIOS still tries to access it, or otherwise assumes that it's in D0.
> > > This is clearly bogus, since ACPI mandates that devices are put into D3
> > > by the OSPM if they are not wake-up sources. In the future we want to
> > > unify more of the driver's runtime and system suspend paths, for example
> > > by skipping all the system suspend/hibernation hooks if the device is
> > > runtime suspended already. Accordingly for all other platforms the goal
> > > is still to properly power down the device during hibernation.
> 
> [snip]
> > 
> > If we see more of these troublesome machines we might need to apply an
> > even bigger hammer like gen < 5 or so. But as long as there's just 1
> > report I think this is the right approach.
> > 
> > Bjorn, as soon as we have your tested-by that this work we can apply this
> > and shovel it through the backporting machinery.
> 
> Isn't there a risk that this will negatively impact machines using gen4
> that *don't* have a buggy BIOS?  Wouldn't a quirk tied to the laptop
> or BIOS version be better suited -- or possibly a parameter that can be
> passed to the driver, which would make it easier to test if others
> suffering from similar symptoms on other systems suffer from the same
> issue or not?
> 
> Just my 2¢.

We've checked today with Ville a few machines we've found from GEN2 to
GEN5+. There was one Thinkpad x61s (GEN4) where I could reproduce the
exact same problem and get rid of it using the same workaround. All the
others were non-Lenovo (including GEN4) mobile and desktop platforms and
none of these had the problem. I also tried it on a Lenovo IVB
ultrabook, which also works fine. So the current theory is that it's
related to GEN4 Thinkpad BIOSes, and so we need to change the condition
to match that at least.

--Imre