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

[Jani Nikula <jani.nikula@intel.com>]

On Tue, 25 Feb 2025, "Manna, Animesh" <animesh.manna@intel.com> wrote:
>> -----Original Message-----
>> From: Nikula, Jani <jani.nikula@intel.com>
>> Sent: Monday, February 24, 2025 4:18 PM
>> To: Manna, Animesh <animesh.manna@intel.com>; intel-
>> gfx@lists.freedesktop.org; intel-xe@lists.freedesktop.org
>> Cc: Hogander, Jouni <jouni.hogander@intel.com>; B, Jeevan
>> <jeevan.b@intel.com>; Manna, Animesh <animesh.manna@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@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@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.

You only modify the register if crtc_state->has_lobf is false. You don't
need to read the register if crtc_state->has_lobf is true.


BR,
Jani.


>
> 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

-- 
Jani Nikula, Intel