[PATCH v6 4/8] drm/i915/lobf: Update lobf if any change in dependent parameters

[Manna, Animesh]

> -----Original Message-----
> From: Hogander, Jouni <jouni.hogander at intel.com>
> Sent: Monday, March 24, 2025 1:36 PM
> To: intel-xe at lists.freedesktop.org; Manna, Animesh
> <animesh.manna at intel.com>; intel-gfx at lists.freedesktop.org
> Cc: Nikula, Jani <jani.nikula at intel.com>; B, Jeevan <jeevan.b at intel.com>
> Subject: Re: [PATCH v6 4/8] drm/i915/lobf: Update lobf if any change in
> dependent parameters
> 
> On Thu, 2025-03-20 at 00:45 +0530, Animesh Manna wrote:
> > For every commit the dependent condition for LOBF is checked and
> > accordingly update has_lobf flag which will be used to update the
> > ALPM_CTL register during commit.
> >
> > v1: Initial version.
> > v2: Avoid reading h/w register without has_lobf check. [Jani]
> > v3: Update LOBF in post plane update instead of separate function.
> > [Jouni]
> >
> > Signed-off-by: Animesh Manna <animesh.manna at intel.com>
> > ---
> >  drivers/gpu/drm/i915/display/intel_alpm.c | 5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/i915/display/intel_alpm.c
> > b/drivers/gpu/drm/i915/display/intel_alpm.c
> > index c2862888466f..5df1253a6b6c 100644
> > --- a/drivers/gpu/drm/i915/display/intel_alpm.c
> > +++ b/drivers/gpu/drm/i915/display/intel_alpm.c
> > @@ -378,9 +378,12 @@ void intel_alpm_post_plane_update(struct
> > intel_atomic_state *state,
> >  	struct intel_display *display = to_intel_display(state);
> >  	const struct intel_crtc_state *crtc_state =
> >  		intel_atomic_get_new_crtc_state(state, crtc);
> > +	const struct intel_crtc_state *old_crtc_state =
> > +		intel_atomic_get_old_crtc_state(state, crtc);
> >  	struct intel_encoder *encoder;
> >
> > -	if (!crtc_state->has_lobf && !crtc_state->has_psr)
> > +	if (!crtc_state->has_lobf && !crtc_state->has_psr &&
> > +	    !old_crtc_state->has_lobf)
> 
> I don't really understand this change? Where lobf is disabled when has_lobf
> is false?

When crtc_state->has_lobf = false and old_crtc_state->has_lobf = true,
then (!crtc_state->has_lobf && !crtc_state->has_psr && !old_crtc_state->has_lobf) = false, so return will not happen.
Next lnl_alpm_configure() will program other aux-wake/aux-less alpm related bits except lobf-enable. Do you see any issue here?

Regards,
Animesh
> 
> BR,
> 
> Jouni Högander
> >  		return;
> >
> >  	for_each_intel_encoder_mask(display->drm, encoder,