[Intel-gfx] Reviving the LPSS PWM patches

[Lluís Batlle i Rossell]

On Tue, Apr 05, 2016 at 09:06:25PM +0200, Lluís Batlle i Rossell wrote:
> On Tue, Apr 05, 2016 at 12:39:30PM +0200, Lluís Batlle i Rossell wrote:
> > On Tue, Apr 05, 2016 at 12:03:44PM +0530, Kumar, Shobhit wrote:
> > > On Thursday 31 March 2016 03:57 PM, Lluís Batlle i Rossell wrote:
> > > >Hello,
> > > >
> > > >I saw that you did some work for LPSS PWM:
> > > >https://lists.freedesktop.org/archives/intel-gfx/2016-January/085006.html
> > 
> > Definitely I was quite blind in my initial attempts at applying the
> > patches, and gave me the idea that they did not apply in any recent tree.
> > I've checked that they apply and build over the released 4.5, so I will go
> > testing that, maybe today. I will report.
> 
> The screen goes black, as before.
> 
> I attach the dmesg after applying the four patches (3 + 1) to 4.5.
> PWM_LPSS=y and PWM_LPSS_PLATFORM=y
> 
> I also attach a dmesg of a panicked kernel that actually does run in that
> board, so you can see that it is actually a lpss-pwm case.

I don't see any trace of pwm/lpss in dmesg, so it's normal that i915 fails
to find it. I wonder if there may be a problem in the ACPI table. I have
the DSDT and it clearly reports the:

Name (_CID, "80860F09")  // _CID: Compatible ID
Name (_DDN, "Intel(R) PWM Controller #2 - 80860F09")  // _DDN: DOS Device Name

Which should be the lpss pwm. But somehow it is not loaded, so I guess it
fails the probing.

Maybe the DSDT is broken, and I should fix and recompile a new one for the
pwm controller to work? I don't really know how this things work, and
whether the kernel should report anything special if it were the case of a
broken DSDT.

Regards,
Lluḉis.

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