[coreboot] Question about Intel HD graphics and FLR

[Zoran Stojsavljevic]

OK, Joshua!

I do not promise anything. But I, out of (your) desperation, will try to
find answers for you. If (no promise)...

If I (eventually) return back, I have only one condition for you: NEVER ask
how I found (any future) answer for/to you!

Thank you,
Zoran

On Thu, Mar 30, 2017 at 5:48 PM, Joshua Pincus <joshua.pincus at gmail.com>
wrote:

> Hi Zoran,
>
> Thanks for your reply.
>
> My situation is this: When the VM guest comes up the first time from a
> system-level reset (aka power on), the Broadwell HD graphics device runs
> fine.  I see basic VGA both before and during the boot of Windows.  Once
> Windows boots, the HD graphics device is configured by Intel's driver and I
> see hi-rez output.  On a reboot of Windows within the VM, an FLR is
> issued.  When the guest comes back up, no VGA.  Windows does boot but
> provides no VGA output.  If Windows needs to drop into VGA mode so that a
> user can access the real-mode functionality of the recovery console, still
> no VGA.
>
> It's only on Broadwell-based boards that we have this problem.  If we
> issue FLRs during the reset of the PCI bus for older Intel boards, no
> problem.  We get VGA.  Something involved with the FLR is messing up the
> state of the hardware instead of actually returning the hardware to a
> virgin state, akin to what you would get from a full system reset.
>
> I was wondering if anyone had seen this kind of behavior.  We've tried
> everything.  We've manipulated all of the obvious HD graphics MMIO
> registers involved with restoring VGA but nothing seems to work.
>
> Thanks,
> JP
>
> On Thu, Mar 30, 2017 at 4:29 AM, Zoran Stojsavljevic <
> zoran.stojsavljevic at gmail.com> wrote:
>
>> Hello Joshua,
>>
>> I'll ask similar question, considering UEFI (BIOS). I have no idea if you
>> can issue somehow easy FLR (PCI Function Level Reset), but if you can,
>> does this use case repeat itself?
>>
>> I found, related to BIOS, this pointer (http://www.tomshardware.co.uk
>> /forum/278002-30-solved-what-capability-option-bios), since I do NOT
>> recall this option in any (legacy and UEFI) of the BIOSes I used (and I
>> used lot (>100) of them). Probably, did not pay too much attention, since I
>> do not recall this option to be tested/used?!
>>
>> Zoran
>>
>> On Wed, Mar 29, 2017 at 10:49 PM, Joshua Pincus <joshua.pincus at gmail.com>
>> wrote:
>>
>>> Hi,
>>>
>>> After performing just an FLR (PCI function level reset) of a Gen8 Intel
>>> HD graphics device, there's no VGA output from the device, no matter what I
>>> try to do.  I've had coreboot reset the graphics control register, VGA
>>> control, VGA display disable bit, etc.
>>>
>>> Has anyone seen anything like this?  The only way I can get VGA restored
>>> is by performing a system-level reset.  But I just want to do an FLR.  Any
>>> ideas?
>>>
>>> Thanks,
>>> JP
>>>
>>> --
>>> coreboot mailing list: coreboot at coreboot.org
>>> https://www.coreboot.org/mailman/listinfo/coreboot
>>>
>>
>>
>
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