Re: [Intel-gfx] [PATCH 2/3] drm/i915/pps: Enable 2nd pps for dual EDP scenario

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

On Wed, 09 Nov 2022, "Manna, Animesh" <animesh.manna@intel.com> wrote:
>> -----Original Message-----
>> From: Nikula, Jani <jani.nikula@intel.com>
>> Sent: Wednesday, November 9, 2022 5:12 PM
>> To: Manna, Animesh <animesh.manna@intel.com>; intel-
>> gfx@lists.freedesktop.org
>> Cc: Manna, Animesh <animesh.manna@intel.com>; Ville Syrjälä
>> <ville.syrjala@linux.intel.com>; Shankar, Uma <uma.shankar@intel.com>
>> Subject: Re: [PATCH 2/3] drm/i915/pps: Enable 2nd pps for dual EDP scenario
>>
>> On Wed, 09 Nov 2022, Animesh Manna <animesh.manna@intel.com> wrote:
>> > From display gen12 onwards to support dual EDP two instances of pps added.
>> > Currently backlight controller and pps instance can be mapped together
>> > for a specific panel. Currently dual PPS support is broken. This patch
>> > fixes it and enables for display 12+.
>> >
>> > v1: Iniital revision.
>> > v2: Called intel_bios_panel_init w/o PNPID before intel_pps_init.
>> > [Jani]
>> > v3: Set pps_id to -1 for pnpid type of panel which will be used by
>> > bxt_power_sequencer_idx() to set 2nd pps instance as default for 2nd
>> > EDP panel. [Jani]
>> > v4: Early return for PANEL_TYPE_FALLBACK. [Jani]
>> > v5: Removed additional pps_id variable and reused backlight
>> > controller. [Jani]
>> >
>> > Cc: Jani Nikula <jani.nikula@intel.com>
>> > Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
>> > Cc: Uma Shankar <uma.shankar@intel.com>
>> > Signed-off-by: Animesh Manna <animesh.manna@intel.com>
>> > ---
>> >  drivers/gpu/drm/i915/display/intel_bios.c |  9 ++++++++-
>> > drivers/gpu/drm/i915/display/intel_bios.h |  2 +-
>> >  drivers/gpu/drm/i915/display/intel_dp.c   | 10 +++++++---
>> >  drivers/gpu/drm/i915/display/intel_pps.c  | 12 +++++++++++-
>> >  4 files changed, 27 insertions(+), 6 deletions(-)
>> >
>> > diff --git a/drivers/gpu/drm/i915/display/intel_bios.c
>> > b/drivers/gpu/drm/i915/display/intel_bios.c
>> > index c2987f2c2b2e..1c1eea061fbb 100644
>> > --- a/drivers/gpu/drm/i915/display/intel_bios.c
>> > +++ b/drivers/gpu/drm/i915/display/intel_bios.c
>> > @@ -3183,7 +3183,7 @@ void intel_bios_init(struct drm_i915_private *i915)
>> >     kfree(oprom_vbt);
>> >  }
>> >
>> > -void intel_bios_init_panel(struct drm_i915_private *i915,
>> > +bool intel_bios_init_panel(struct drm_i915_private *i915,
>> >                        struct intel_panel *panel,
>> >                        const struct intel_bios_encoder_data *devdata,
>> >                        const struct edid *edid)
>> > @@ -3192,6 +3192,11 @@ void intel_bios_init_panel(struct
>> > drm_i915_private *i915,
>> >
>> >     panel->vbt.panel_type = get_panel_type(i915, devdata, edid);
>> >
>> > +   if (panel->vbt.panel_type == PANEL_TYPE_FALLBACK && !edid) {
>>
>> As Ville pointed out, "panel->vbt.panel_type == PANEL_TYPE_FALLBACK" is
>> comparing apples to oranges, and we hit this path only in the rare case that
>> panel_type == 3, regardless of where the panel type originated.
>
> Got it, tried returning some random negative number (for example -2) from fallback_get_panel_type() and checking the same here is fixing the WARN_ON.
>
>>
>> This is probably the reason patches 1&2 don't fix the original issue like it should.
>>
>> I remind you that the issue is two eDP having their own pps software states but
>> using the same pps hardware due to conflicting pps index (which is the same as
>> panel->vbt.backlight.controller). This is what we need to solve here.
>
> In this patch we decide to use the specific pps based on port number. Once we identify it is PORT B always 2nd instance of PPS will be used. All pps register get instantiated with pps_idx 1
>         if (backlight_controller == -1) {
>                 /*
>                  * Use 2nd PPS instance as default for 2nd EDP panel.
>                  */
>                 if (connector->encoder->port == PORT_A)
>                         return 0;
>                 else
>                         return 1;
>         }
> Not sure what is toggling the VDD.

The 2nd eDP obviously!

BR,
Jani.


> Anyways I agree patch 3 is not
> needed. Thanks for review.
>
> Regards,
> Animesh
>
>>
>> We get the wakeref imbalance because of two eDP trampling on the same pps
>> hardware. Patch 3 does nothing to address that issue, it just tries to hide the
>> problem.
>>
>>
>> BR,
>> Jani.
>>
>>
>> > +           panel->vbt.backlight.controller = -1;
>> > +           return true;
>> > +   }
>> > +
>> >     parse_panel_options(i915, panel);
>> >     parse_generic_dtd(i915, panel);
>> >     parse_lfp_data(i915, panel);
>> > @@ -3203,6 +3208,8 @@ void intel_bios_init_panel(struct drm_i915_private
>> *i915,
>> >     parse_psr(i915, panel);
>> >     parse_mipi_config(i915, panel);
>> >     parse_mipi_sequence(i915, panel);
>> > +
>> > +   return false;
>> >  }
>> >
>> >  /**
>> > diff --git a/drivers/gpu/drm/i915/display/intel_bios.h
>> > b/drivers/gpu/drm/i915/display/intel_bios.h
>> > index e375405a7828..f8ef0274f3ee 100644
>> > --- a/drivers/gpu/drm/i915/display/intel_bios.h
>> > +++ b/drivers/gpu/drm/i915/display/intel_bios.h
>> > @@ -232,7 +232,7 @@ struct mipi_pps_data {  } __packed;
>> >
>> >  void intel_bios_init(struct drm_i915_private *dev_priv); -void
>> > intel_bios_init_panel(struct drm_i915_private *dev_priv,
>> > +bool intel_bios_init_panel(struct drm_i915_private *dev_priv,
>> >                        struct intel_panel *panel,
>> >                        const struct intel_bios_encoder_data *devdata,
>> >                        const struct edid *edid);
>> > diff --git a/drivers/gpu/drm/i915/display/intel_dp.c
>> > b/drivers/gpu/drm/i915/display/intel_dp.c
>> > index 7400d6b4c587..78cf3a77f026 100644
>> > --- a/drivers/gpu/drm/i915/display/intel_dp.c
>> > +++ b/drivers/gpu/drm/i915/display/intel_dp.c
>> > @@ -5235,6 +5235,7 @@ static bool intel_edp_init_connector(struct intel_dp
>> *intel_dp,
>> >     struct intel_encoder *encoder = &dp_to_dig_port(intel_dp)->base;
>> >     bool has_dpcd;
>> >     struct edid *edid;
>> > +   bool retry;
>> >
>> >     if (!intel_dp_is_edp(intel_dp))
>> >             return true;
>> > @@ -5254,6 +5255,9 @@ static bool intel_edp_init_connector(struct intel_dp
>> *intel_dp,
>> >             return false;
>> >     }
>> >
>> > +   retry = intel_bios_init_panel(dev_priv, &intel_connector->panel,
>> > +                                 encoder->devdata, NULL);
>> > +
>> >     intel_pps_init(intel_dp);
>> >
>> >     /* Cache DPCD and EDID for edp. */
>> > @@ -5288,9 +5292,9 @@ static bool intel_edp_init_connector(struct intel_dp
>> *intel_dp,
>> >             edid = ERR_PTR(-ENOENT);
>> >     }
>> >     intel_connector->edid = edid;
>> > -
>> > -   intel_bios_init_panel(dev_priv, &intel_connector->panel,
>> > -                         encoder->devdata, IS_ERR(edid) ? NULL : edid);
>> > +   if (retry)
>> > +           intel_bios_init_panel(dev_priv, &intel_connector->panel,
>> > +                                 encoder->devdata, IS_ERR(edid) ? NULL :
>> edid);
>> >
>> >     intel_panel_add_edid_fixed_modes(intel_connector, true);
>> >
>> > diff --git a/drivers/gpu/drm/i915/display/intel_pps.c
>> > b/drivers/gpu/drm/i915/display/intel_pps.c
>> > index 3949fb449353..5738af154bd2 100644
>> > --- a/drivers/gpu/drm/i915/display/intel_pps.c
>> > +++ b/drivers/gpu/drm/i915/display/intel_pps.c
>> > @@ -219,6 +219,16 @@ bxt_power_sequencer_idx(struct intel_dp *intel_dp)
>> >     /* We should never land here with regular DP ports */
>> >     drm_WARN_ON(&dev_priv->drm, !intel_dp_is_edp(intel_dp));
>> >
>> > +   if (backlight_controller == -1) {
>> > +           /*
>> > +            * Use 2nd PPS instance as default for 2nd EDP panel.
>> > +            */
>> > +           if (connector->encoder->port == PORT_A)
>> > +                   return 0;
>> > +           else
>> > +                   return 1;
>> > +   }
>> > +
>> >     if (!intel_dp->pps.pps_reset)
>> >             return backlight_controller;
>> >
>> > @@ -1430,7 +1440,7 @@ void intel_pps_init(struct intel_dp *intel_dp)
>> >     intel_dp->pps.initializing = true;
>> >     INIT_DELAYED_WORK(&intel_dp->pps.panel_vdd_work,
>> > edp_panel_vdd_work);
>> >
>> > -   if (IS_GEMINILAKE(i915) || IS_BROXTON(i915))
>> > +   if (IS_GEMINILAKE(i915) || IS_BROXTON(i915) || DISPLAY_VER(i915) >=
>> > +12)
>> >             intel_dp->get_pps_idx = bxt_power_sequencer_idx;
>> >     else if (IS_VALLEYVIEW(i915) || IS_CHERRYVIEW(i915))
>> >             intel_dp->get_pps_idx = vlv_power_sequencer_pipe;
>>
>> --
>> Jani Nikula, Intel Open Source Graphics Center

-- 
Jani Nikula, Intel Open Source Graphics Center