[PATCH v4 4/8] drm/i915/lobf: Update lobf if any change in dependent parameters

[Manna, Animesh]

> -----Original Message-----
> From: Nikula, Jani <jani.nikula at intel.com>
> Sent: Monday, February 24, 2025 4:18 PM
> To: Manna, Animesh <animesh.manna at intel.com>; intel-
> gfx at lists.freedesktop.org; intel-xe at lists.freedesktop.org
> Cc: Hogander, Jouni <jouni.hogander at intel.com>; B, Jeevan
> <jeevan.b at intel.com>; Manna, Animesh <animesh.manna at intel.com>
> Subject: Re: [PATCH v4 4/8] drm/i915/lobf: Update lobf if any change in
> dependent parameters
> 
> On Mon, 24 Feb 2025, Animesh Manna <animesh.manna at intel.com> 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.
> >
> > Signed-off-by: Animesh Manna <animesh.manna at intel.com>
> > ---
> >  drivers/gpu/drm/i915/display/intel_alpm.c | 16 ++++++++++++++++
> > drivers/gpu/drm/i915/display/intel_alpm.h |  1 +
> > drivers/gpu/drm/i915/display/intel_ddi.c  |  2 ++
> >  3 files changed, 19 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/i915/display/intel_alpm.c
> > b/drivers/gpu/drm/i915/display/intel_alpm.c
> > index 1438e125cde1..83719ee1721c 100644
> > --- a/drivers/gpu/drm/i915/display/intel_alpm.c
> > +++ b/drivers/gpu/drm/i915/display/intel_alpm.c
> > @@ -312,6 +312,22 @@ void intel_alpm_lobf_compute_config(struct
> intel_dp *intel_dp,
> >  		(first_sdp_position + waketime_in_lines);  }
> >
> > +void intel_alpm_lobf_update(const struct intel_crtc_state
> > +*crtc_state) {
> > +	struct intel_display *display = to_intel_display(crtc_state);
> > +	enum transcoder cpu_transcoder = crtc_state->cpu_transcoder;
> > +	u32 alpm_ctl;
> > +
> > +	if (DISPLAY_VER(display) < 20)
> > +		return;
> > +
> > +	alpm_ctl = intel_de_read(display, ALPM_CTL(display,
> cpu_transcoder));
> > +	if (alpm_ctl & ALPM_CTL_LOBF_ENABLE && !crtc_state->has_lobf) {
> 
> You don't need to even read the register if crtc_state->has_lobf is true.

Thanks Jani for review.
Reading register to get what is there in ALPM_CTL register, like aux-less or aux-wake alpm and etc.
For LOBF we need to touch a specific bit, and don't want to modify other bitfields.

Regards,
Animesh

> 
> > +		alpm_ctl &= ~ALPM_CTL_LOBF_ENABLE;
> > +		intel_de_write(display, ALPM_CTL(display, cpu_transcoder),
> alpm_ctl);
> > +	}
> > +}
> > +
> >  static void lnl_alpm_configure(struct intel_dp *intel_dp,
> >  			       const struct intel_crtc_state *crtc_state)  { diff --
> git
> > a/drivers/gpu/drm/i915/display/intel_alpm.h
> > b/drivers/gpu/drm/i915/display/intel_alpm.h
> > index 91f51fb24f98..c6efd25c2062 100644
> > --- a/drivers/gpu/drm/i915/display/intel_alpm.h
> > +++ b/drivers/gpu/drm/i915/display/intel_alpm.h
> > @@ -23,6 +23,7 @@ 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_lobf_update(const struct intel_crtc_state
> > +*crtc_state);
> >  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_ddi.c
> > b/drivers/gpu/drm/i915/display/intel_ddi.c
> > index 26aa32d4d50e..44258ba0d951 100644
> > --- a/drivers/gpu/drm/i915/display/intel_ddi.c
> > +++ b/drivers/gpu/drm/i915/display/intel_ddi.c
> > @@ -37,6 +37,7 @@
> >  #include "icl_dsi.h"
> >  #include "intel_alpm.h"
> >  #include "intel_audio.h"
> > +#include "intel_alpm.h"
> >  #include "intel_audio_regs.h"
> >  #include "intel_backlight.h"
> >  #include "intel_combo_phy.h"
> > @@ -3621,6 +3622,7 @@ static void intel_ddi_update_pipe_dp(struct
> intel_atomic_state *state,
> >  	intel_ddi_set_dp_msa(crtc_state, conn_state);
> >
> >  	intel_dp_set_infoframes(encoder, true, crtc_state, conn_state);
> > +	intel_alpm_lobf_update(crtc_state);
> >
> >  	intel_backlight_update(state, encoder, crtc_state, conn_state);
> >  	drm_connector_update_privacy_screen(conn_state);
> 
> --
> Jani Nikula, Intel