[Intel-gfx] [PATCH] drm/i915: Handle changing enable_psr parameter at runtime better

[Pandiyan, Dhinakaran]

On Thu, 2018-03-08 at 18:52 +0100, Maarten Lankhorst wrote:
> Op 08-03-18 om 18:43 schreef Pandiyan, Dhinakaran:
> >
> >
> > On Thu, 2018-03-08 at 08:07 +0100, Maarten Lankhorst wrote:
> >> Op 07-03-18 om 23:22 schreef Pandiyan, Dhinakaran:
> >>> On Wed, 2018-03-07 at 17:39 +0100, Maarten Lankhorst wrote:
> >>>> Similar to enable_fbc, enable_psr was ignored at runtime if it was
> >>>> changed. The easiest fix is to pretend enable_psr is ignored at
> >>>> configure time, and never activate it for !enable_psr, so both cases
> >>>> are handled without modesets.
> >>> What about cases where psr_flush() is not called and consequently the
> >>> module parameter is not checked? With HW tracking, PSR is
> >>> enabled/disabled during modeset and the hardware is expected to exit and
> >>> activate PSR without driver intervention.
> >> It looks like intel_frontbuffer_flush always calls intel_psr_flush,
> >> so we at least get a PSR toggle after every atomic commit?
> > I have a patch to remove flush() from legacy_cursor_update(). We end up
> > with an inconsistent behavior when that patch gets merged,
> > cursor moves -> trigger psr exit but don't read module parameter
> > commits -> trigger psr exit but read module parameter
> Legacy cursor updates are special, I don't mind them not changing PSR.
> > Eventually, when we get to removing flush() from commits, then this
> > patch won't really be useful. And tests disabling/enabling PSR at
> > runtime will probably fail.
> Could we transition to debugfs for changing it at runtime?

That does sound like a better idea.

> 
> ~Maarten