[PATCH] modesetting: fail PreInit() if the device has zero connectors

[Dave Airlie]

On 24 October 2017 at 02:42, Tobias Jakobi
<tjakobi at math.uni-bielefeld.de> wrote:
> Hello Hans,
>
>
> Hans de Goede wrote:
>> Hi,
>>
>> On 20-10-17 19:08, tobias.jakobi1 at uni-bielefeld.de wrote:
>>> On laptop systems with a dedicated (powerful) GPU A, you usually
>>> have all connectors routed to another (less-powerful) GPU B.
>>>
>>> With my setup (GPU A = Nvidia, GPU B = Intel) I keep GPU A switched
>>> off by not loading the nouveau kernel driver during boot.
>>>
>>> Loading nouveau while X is running then crashes the server:
>>> [   540.775] (EE) 0: /usr/bin/X (xorg_backtrace+0x41) [0x57fa31]
>>> [   540.775] (EE) 1: /usr/bin/X (0x400000+0x183429) [0x583429]
>>> [   540.775] (EE) 2: /lib64/libpthread.so.0 (0x7ff02d508000+0x10ec0)
>>> [0x7ff02d518ec0]
>>> [   540.775] (EE) 3: /lib64/libc.so.6 (gsignal+0x38) [0x7ff02d1a2178]
>>> [   540.775] (EE) 4: /lib64/libc.so.6 (abort+0x16a) [0x7ff02d1a35fa]
>>> [   540.775] (EE) 5: /lib64/libc.so.6 (0x7ff02d16f000+0x2c0b7) [0x7ff02d19b0b7]
>>> [   540.775] (EE) 6: /lib64/libc.so.6 (0x7ff02d16f000+0x2c162) [0x7ff02d19b162]
>>> [   540.775] (EE) 7: /usr/bin/X (dixRegisterPrivateKey+0x247) [0x452197]
>>> [   540.775] (EE) 8: /usr/lib64/xorg/modules/libglamoregl.so
>>> (glamor_init+0x160) [0x7ff00ee564d0]
>>> [   540.775] (EE) 9: /usr/lib64/xorg/modules/drivers/modesetting_drv.so
>>> (0x7ff01c19a000+0x83e1) [0x7ff01c1a23e1]
>>> [   540.775] (EE) 10: /usr/bin/X (AddGPUScreen+0xf3) [0x4348b3]
>>> [   540.775] (EE) 11: /usr/bin/X (0x400000+0x90271) [0x490271]
>>> [   540.775] (EE) 12: /usr/bin/X (0x400000+0x9547b) [0x49547b]
>>> [   540.775] (EE) 13: /usr/bin/X (0x400000+0x905d7) [0x4905d7]
>>> [   540.775] (EE) 14: /usr/bin/X (xf86VTEnter+0x1bb) [0x47399b]
>>> [   540.775] (EE) 15: /usr/bin/X (WakeupHandler+0xda) [0x438e3a]
>>> [   540.775] (EE) 16: /usr/bin/X (WaitForSomething+0x1ce) [0x57d6fe]
>>> [   540.775] (EE) 17: /usr/bin/X (0x400000+0x34221) [0x434221]
>>> [   540.775] (EE) 18: /usr/bin/X (0x400000+0x382f8) [0x4382f8]
>>> [   540.775] (EE) 19: /lib64/libc.so.6 (__libc_start_main+0xf0) [0x7ff02d18f670]
>>> [   540.776] (EE) 20: /usr/bin/X (_start+0x29) [0x4235b9]
>>>
>>> In particular note that GLAMOR is initialized for GPU A, which
>>> makes no sense since it has no connectors.
>>>
>>> Fix this by bailing out early in the modesetting DDX when a setup
>>> with zero connectors is detected.
>>>
>>> Signed-off-by: Tobias Jakobi <tjakobi at math.uni-bielefeld.de>
>>
>> Sorry, but NACK. The modesetting driver actually had such a check before
>> and I removed it because not having a driver breaks rendering on
>> the dedicated GPU with "DRI_PRIME=1" for dri2 clients.
> sorry, I didn't consider DRI2 in this scenario.
>
>
>> I guess that there is some sort of assumption in the code for dealing
>> with glamor failure that it only happens on coldplug, if you really
>> want to be able to modprobe nouveau later you should figure out what
>> is exactly going wrong and fix that.
> OK, I'll try to get to the bottom of this.
>
>
>> Note BTW that nouveau should runtime suspend the GPU, even with Xorg
>> running and there really is no need to not load nouveau.
> No, sadly this is not true on my system. The system has a dual cooling solution,
> where cooler A is attached to the CPU, and cooler B to the GPU. When never
> inserting nouveau.ko after boot, cooler B stays off the entire time. Once I've
> inserted the module, cooler B comes up from time to time _even_ if the GPU is
> runtime suspended at that time (and has been since hours).

That seems strange, is the gpu powered down correctly?

It might be nouveau/acpi/pm isn't actually shutting it down.

Dave.