Hi,
On 06-06-18 11:36, Maarten Lankhorst wrote:
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.
Right but the "mode is not compatible" check will be always
necessary, because e.g. some BIOs-es insist in bringing
up the display in 1024x768 instead of its native mode.
What I meant is, something like check which generation we are on
(and maybe if a specific type of output is used or not if that
does not convolute the code too much).
E.g. you mention vblank issues with haswell/broadwell eDP,
so if i915.fastboot=-1 we would then disable fastboot
if we are on a haswell or broadwell and eDP is used.
Or we could simply disable it on all haswell/broadwell devices
when i915.fastboot=-1 used, but maybe enable on skylake and
newer?
Regards,
Hans
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