[Intel-gfx] i915 Skylake: "Invalid ROM contents"

[Andy Lutomirski]

On Wed, Nov 18, 2015 at 8:12 AM, Daniel Stone <daniel at fooishbar.org> wrote:
> Hi,
>
> On 18 November 2015 at 15:59, Andy Lutomirski <luto at amacapital.net> wrote:
>> On Wed, Nov 18, 2015 at 2:59 AM, Ville Syrjälä
>> <ville.syrjala at linux.intel.com> wrote:
>>> On Tue, Nov 17, 2015 at 11:43:25AM -0800, Andy Lutomirski wrote:
>>>> Typing:
>>>>
>>>> # cat /sys/devices/pci0000:00/0000:00:02.0/rom
>>>>
>>>> Provokes:
>>>>
>>>> i915 0000:00:02.0: Invalid ROM contents
>>>
>>> Hmm. So there's no PCI option ROM there. I wonder what is there. I
>>> get the same on my Braswell BTW. I tried to look through the UEFI
>>> spec a bit, and it seems to say that even for non-legacy option ROMs
>>> the 0x55aa signature should be there.
>>>
>>> But this being the GPU means we may be using the shadow ROM stuff,
>>> which IIRC assumes that the shadow is at 0xc000. I'm not sure that
>>> holds anymore with UEFI, and maybe we should be using some UEFI
>>> trick instead to find out where it actually lives?
>>>
>>> BTW what does 'lspci -vv -s 00:02.0' say on your machine?
>>>
>>
>> 00:02.0 VGA compatible controller: Intel Corporation Sky Lake
>> Integrated Graphics (rev 07) (prog-if 00 [VGA controller])
>>     DeviceName:  Onboard IGD
>>     Subsystem: Dell Device 0704
>>     Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop-
>> ParErr- Stepping- SERR- FastB2B- DisINTx+
>>     Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort-
>> <TAbort- <MAbort- >SERR- <PERR- INTx-
>>     Latency: 0
>>     Interrupt: pin A routed to IRQ 128
>>     Region 0: Memory at db000000 (64-bit, non-prefetchable) [size=16M]
>>     Region 2: Memory at 90000000 (64-bit, prefetchable) [size=256M]
>>     Region 4: I/O ports at f000 [size=64]
>>     Expansion ROM at <unassigned> [disabled]
>
> UEFI has an option to enable option ROMs, which is disabled by
> default; I wonder if having it disabled prevents all access to the
> ROM.
>
> Mind you, it doesn't seem to be fatal; I've not had any issues with
> the same machine that I can pin down to lack of ROM.
>

FWIW, my logs also get spammed with:

[  127.101881] i915 0000:00:02.0: BAR 6: [??? 0x00000000 flags 0x2]
has bogus alignment

I suspect that the PCI core is just failing to recognize that the ROM
is disabled.

--Andy