> -----Original Message-----
> From: Manna, Animesh
> Sent: Tuesday, April 22, 2025 7:47 PM
> To: Hogander, Jouni <jouni.hogan...@intel.com>; intel-
> x...@lists.freedesktop.org; intel-gfx@lists.freedesktop.org
> Cc: Nikula, Jani <jani.nik...@intel.com>; B, Jeevan <jeeva...@intel.com>
> Subject: RE: [PATCH v9 06/10] drm/i915/lobf: Update lobf if any change in
> dependent parameters
>
>
>
> > -----Original Message-----
> > From: Hogander, Jouni <jouni.hogan...@intel.com>
> > Sent: Tuesday, April 22, 2025 5:19 PM
> > To: intel...@lists.freedesktop.org; Manna, Animesh
> > <animesh.ma...@intel.com>; intel-gfx@lists.freedesktop.org
> > Cc: Nikula, Jani <jani.nik...@intel.com>; B, Jeevan
> > <jeeva...@intel.com>
> > Subject: Re: [PATCH v9 06/10] drm/i915/lobf: Update lobf if any change
> > in dependent parameters
> >
> > On Thu, 2025-04-17 at 15:11 +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]
> > > v4:
> > > - Add lobf disable print. [Jouni]
> > > - Simplify condition check for enabling/disabling lobf. [Jouni]
> > > v5: Disable LOBF in pre_plane_update(). [Jouni]
> > >
> > > Signed-off-by: Animesh Manna <animesh.ma...@intel.com>
> > > ---
> > > drivers/gpu/drm/i915/display/intel_alpm.c | 43
> > > +++++++++++++++++++-
> > > drivers/gpu/drm/i915/display/intel_alpm.h | 2 +
> > > drivers/gpu/drm/i915/display/intel_display.c | 1 +
> > > 3 files changed, 45 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/gpu/drm/i915/display/intel_alpm.c
> > > b/drivers/gpu/drm/i915/display/intel_alpm.c
> > > index 01949b90c0c3..3fbe8eca1301 100644
> > > --- a/drivers/gpu/drm/i915/display/intel_alpm.c
> > > +++ b/drivers/gpu/drm/i915/display/intel_alpm.c
> > > @@ -376,15 +376,56 @@ void intel_alpm_configure(struct intel_dp
> > > *intel_dp,
> > > intel_dp->alpm_parameters.transcoder = crtc_state-
> > > >cpu_transcoder;
> > > }
> > >
> > > +void intel_alpm_pre_plane_update(struct intel_atomic_state *state,
> > > + struct intel_crtc *crtc)
> > > +{
> > > + struct intel_display *display = to_intel_display(state);
> > > + const struct intel_crtc_state *crtc_state =
> > > + intel_atomic_get_new_crtc_state(state, crtc);
> > > + enum transcoder cpu_transcoder = crtc_state->cpu_transcoder;
> > > + struct intel_encoder *encoder;
> > > + u32 alpm_ctl;
> > > +
> > > + if (DISPLAY_VER(display) < 20)
> > > + return;
> > > +
> > > + if (crtc_state->has_lobf)
> > > + return;
> > > +
> > > + for_each_intel_encoder_mask(display->drm, encoder,
> > > + crtc_state->uapi.encoder_mask) {
> > > + struct intel_dp *intel_dp;
> > > +
> > > + if (!intel_encoder_is_dp(encoder))
> > > + continue;
> > > +
> > > + intel_dp = enc_to_intel_dp(encoder);
> > > +
> > > + if (!intel_dp_is_edp(intel_dp))
> > > + continue;
> > > +
> > > + alpm_ctl = intel_de_read(display, ALPM_CTL(display,
> > > cpu_transcoder));
> >
> > How about if instead of reading you would rely on old_crtc_state-
> > >has_lobf as is done in intel_alpm_post_plane_update ? I think you can
> > write 0 into ALPM_CTL. Parameters are anyways written in
> > intel_alpm_post_plane_update when ALPM is enable for LOBF or PSR.
>
> Writing 0 to ALPM_CTL maybe not good as some bitfields of ALPM_CTL are
> used by DMC And dynamically enabling/disabling LOBF can be impacted
> though it is not very clear from bspec.
> Still do you see this change as nice to have or must have.
>
> Regards,
> Animesh
>
> >
> > BR,
> >
> > Jouni Högander
> > > +
> > > + if (alpm_ctl & ALPM_CTL_LOBF_ENABLE) {
> > > + alpm_ctl &= ~ALPM_CTL_LOBF_ENABLE;
> > > + intel_de_write(display, ALPM_CTL(display,
> > > cpu_transcoder), alpm_ctl);
> > > + drm_dbg_kms(display->drm, "Link off between
> > > frames (LOBF) disabled\n");
> > > + }
> > > + }
> > > +}
> > > +
> > > void intel_alpm_post_plane_update(struct intel_atomic_state *state,
> > > struct intel_crtc *crtc)
> > > {
> > > 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_lobf == old_crtc_state->has_lobf) &&
> > > !crtc_state->has_psr)
The above condition check will not allow to reprogram the ALPM_CTL twice during
LOBF disablement.
Regards,
Animesh
> > > return;
> > >
> > > for_each_intel_encoder_mask(display->drm, encoder, diff --git
> > > a/drivers/gpu/drm/i915/display/intel_alpm.h
> > > b/drivers/gpu/drm/i915/display/intel_alpm.h
> > > index 91f51fb24f98..77bae022a0ea 100644
> > > --- a/drivers/gpu/drm/i915/display/intel_alpm.h
> > > +++ b/drivers/gpu/drm/i915/display/intel_alpm.h
> > > @@ -23,6 +23,8 @@ void intel_alpm_lobf_compute_config(struct
> > > intel_dp *intel_dp,
> > > struct drm_connector_state
> > > *conn_state);
> > > void intel_alpm_configure(struct intel_dp *intel_dp,
> > > const struct intel_crtc_state
> > > *crtc_state);
> > > +void intel_alpm_pre_plane_update(struct intel_atomic_state *state,
> > > + struct intel_crtc *crtc);
> > > void intel_alpm_post_plane_update(struct intel_atomic_state *state,
> > > struct intel_crtc *crtc);
> > > void intel_alpm_lobf_debugfs_add(struct intel_connector
> > > *connector); diff --git
> > > a/drivers/gpu/drm/i915/display/intel_display.c
> > > b/drivers/gpu/drm/i915/display/intel_display.c
> > > index 96a95bc9d5bf..f91401ebdd1a 100644
> > > --- a/drivers/gpu/drm/i915/display/intel_display.c
> > > +++ b/drivers/gpu/drm/i915/display/intel_display.c
> > > @@ -1177,6 +1177,7 @@ static void intel_pre_plane_update(struct
> > > intel_atomic_state *state,
> > > intel_atomic_get_new_crtc_state(state, crtc);
> > > enum pipe pipe = crtc->pipe;
> > >
> > > + intel_alpm_pre_plane_update(state, crtc);
> > > intel_psr_pre_plane_update(state, crtc);
> > >
> > > if (intel_crtc_vrr_disabling(state, crtc)) {
