[Intel-gfx] Enabling i915.fastboot=1 by default

[Maarten Lankhorst]

Op 06-06-18 om 11:09 schreef Hans de Goede:
> Hi All,
>
> So I'm working on making Linux boot in a complete
> flickerfree manner (no modesets, no black screens).
>
> I have this working on various machines with Intel
> gfx, but I need to pass i915.fastboot=1 on the kernel
> commandline.
>
> I know there was some talk about enabling this by
> default a while ago, but it seems that that still
> has not happened (yet?).
>
> I'm wondering what is holding this back ? Maybe we
> can change it from a bool to an int, init it to -1
> and when it is -1 have some automatic detection
> code which disables it where it is known to be
> troublesome and otherwise enables it by default? 

Main reason are bugs like https://bugs.freedesktop.org/show_bug.cgi?id=103781 and our hw
readout not being perfect. On some haswell/broadwell eDP laptops we stop generating vblanks
when we fastboot, and in general we don't trust our code enough for that.

The automatic detection code is already in place, we modeset if the mode is not compatible
enough, but we don't catch all the cases where this might happen.

~Maarten