Re: [PATCH] drm/i915: Handle changing enable_psr parameter at runtime better

[Rodrigo Vivi <rodrigo.vivi@intel.com>]

On Thu, Mar 08, 2018 at 10:07:05AM -0800, Pandiyan, Dhinakaran wrote:
> 
> 
> 
> 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.

+1

> 
> > 
> > ~Maarten
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