Re: genfb console on hybrid graphics

[David Brownlee <abs%netbsd.org@localhost>]

On Thu, 2 Jan 2020 at 20:20, <dhop%nwlink.com@localhost> wrote:
>
> Hi all,
>
> I have a Coffee Lake laptop that runs fine with genfb-- even at 4K-- when
> the BIOS is configured for discrete graphics.  Now, I don't expect either
> i915 or Nouveau to be working yet on this system (Intel UHD 630 and Nvidia
> Quadro RTX4000), but when I configure the BIOS for hybrid graphics to test
> genfb out on the Intel part, I get a 'no console' panic on NetBSD 8, 9.0_RC1
> or -current.  I've tried all the 'gop' modes but I get no console in this
> configuration.
>
> In the hybrid boot case both genfb0 (Nvidia) and genfb1 (Intel) are probed:
>
> genfb0 at pci1 dev 0 funciton 0: NVIDIA product 1eb6 (rev. 0xa1)
> [...]
> genfb1 at pci0 dev 2 function 0: Intel UHD Graphics 630 (rev. 0x82)
>
> ...but the console fails to attach-- I assume because it's trying to use the
> first possible framebuffer which is pointing the secondary device.  What are
> the settings I should be tweaking to test out performance of the Intel
> genfb-- if that's possible?
>
> I'm happy to post boot messages but I'm struggling to find a way forward for
> serial booting this USB-only laptop.

Pity about the BIOS modes - I remember that older Thinkpads had the
full Integrated/Discrete/Optimax option :(

How does the Nvidia probe in the discrete case? I wonder if you could
run boot -c and disable it so its not picked up in hybrid mode

David