Re: [PATCH v4 18/23] drm/i915/display: Introduce new intel_psr_pause/resume function

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On Fri, 2021-05-21 at 11:58 +0100, Mun, Gwan-gyeong wrote:
> On Tue, 2021-05-18 at 14:06 +0300, Ville Syrjälä wrote:
> > On Tue, May 18, 2021 at 09:33:09AM +0000, Mun, Gwan-gyeong wrote:
> > > Hi Ville, 
> > > initially, intel_psr_pause() called intel_psr_disable_locked()
> > > instead
> > > of intel_psr_exit().
> > > In intel_psr_resume(), _intel_psr_enable_locked() was called instead
> > > of
> > > intel_psr_activate().
> > > Can you share what problem the initial code caused when calling
> > > intel_psr_pause() / intel_psr_resume()?
> > 
> > It was doing illegal stuff with crtc->state/etc. That was oopsing.
> > The other problem was that IIRC it was going to do DPCD accesses
> > while the cdclk code was already holding the aux mutexes. I moved it
> > out from under the lock, but I think we might actually want it inside
> > the lock since we'll need that to prevent PSR during all AUX transfers
> > anyway. Putting it back inside the lock should also make it less racy
> > I guess.
> > 
> > > 
> > > In addition, intel_psr_exit() /intel_psr_activate() function  disable
> > > /
> > > enable only the PSR source.
> > > So, if disable/enable for PSR Sink Device is not called together,
> > > there
> > > will be a problem that the PSR state machine of sink and source is
> > > different.
> > > What do you think?
> > 
> > If possible I wouldn't want it touch the sink at all. It should
> > basically be no different to eg. enabling the vblank interrupt.
> > 
> 
> Hi Ville and Stan, 
> Thanks, Ville, for explaining.
> 
> intel_psr_pause() and intel_psr_resume() are an api added to use when
> reactivating (disable and enable) the psr functionality without
> intel_crtc_state and drm_connector_state, as described in the commit
> log.
> And in order to deactivate and activate psr normally, we must
> deactivate the psr functionality of the sink as well, and at this time,
> sink psr deactivate using dpcd.
> 
> And in the part explaining disabling psr in cdclk setting in bspec, the
> following procedure is explained for disabling psr.
> 1. Temporarily disable PSR1, PSR2, and GTC.
> 2. Wait for disabling status from those functions.
> 3. Wait for any pending Aux transactions to complete, and do not start
> any new Aux transaction.
> ...

I don't think we need to disable, psr_exit() + wait until PSR is idle is enough, all other stuff can be left as is.

> 
> So, in my opinion, when the cdclk setting is called from
> intel_atomic_commit_tail() with functions such as
> intel_set_cdclk_pre_plane_update() /
> intel_set_cdclk_post_plane_update(),
> if psr deactivation/activation is necessary, it seems that
> intel_set_cdclk_pre_plane_update() /
> intel_set_cdclk_post_plane_update() should be called with
> intel_psr_enable() / intel_psr_disable() functions together. What do
> you think?
> 
> Br,
> G.G. 
> > > 
> > > On Mon, 2021-05-17 at 09:58 -0700, Souza, Jose wrote:
> > > > On Fri, 2021-05-14 at 20:10 -0700, Matt Roper wrote:
> > > > > From: Gwan-gyeong Mun <gwan-gyeong.mun@xxxxxxxxx>
> > > > > 
> > > > > This introduces the following function that can enable and
> > > > > disable
> > > > > psr
> > > > > without intel_crtc_state/drm_connector_state when intel_psr is
> > > > > already
> > > > > enabled with current intel_crtc_state and drm_connector_state
> > > > > information.
> > > > > 
> > > > > - intel_psr_pause(): Pause current PSR. it deactivates current
> > > > > psr
> > > > > state.
> > > > > - intel_psr_resume(): Resume paused PSR without intel_crtc_state
> > > > > and
> > > > >                       drm_connector_state. It activates paused
> > > > > psr
> > > > > state.
> > > > > 
> > > > > Cc: José Roberto de Souza <jose.souza@xxxxxxxxx>
> > > > > Cc: Stanislav Lisovskiy <stanislav.lisovskiy@xxxxxxxxx>
> > > > > Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> > > > > Signed-off-by: Gwan-gyeong Mun <gwan-gyeong.mun@xxxxxxxxx>
> > > > > Signed-off-by: Matt Roper <matthew.d.roper@xxxxxxxxx>
> > > > > ---
> > > > >  .../drm/i915/display/intel_display_types.h    |  1 +
> > > > >  drivers/gpu/drm/i915/display/intel_psr.c      | 93
> > > > > ++++++++++++++++-
> > > > > --
> > > > >  drivers/gpu/drm/i915/display/intel_psr.h      |  2 +
> > > > >  3 files changed, 82 insertions(+), 14 deletions(-)
> > > > > 
> > > > > diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h
> > > > > b/drivers/gpu/drm/i915/display/intel_display_types.h
> > > > > index b8d1f702d808..ee7cbdd7db87 100644
> > > > > --- a/drivers/gpu/drm/i915/display/intel_display_types.h
> > > > > +++ b/drivers/gpu/drm/i915/display/intel_display_types.h
> > > > > @@ -1482,6 +1482,7 @@ struct intel_psr {
> > > > >         bool sink_support;
> > > > >         bool source_support;
> > > > >         bool enabled;
> > > > > +       bool paused;
> > > > >         enum pipe pipe;
> > > > >         enum transcoder transcoder;
> > > > >         bool active;
> > > > > diff --git a/drivers/gpu/drm/i915/display/intel_psr.c
> > > > > b/drivers/gpu/drm/i915/display/intel_psr.c
> > > > > index 4a63d10876ce..d4df3f5e7918 100644
> > > > > --- a/drivers/gpu/drm/i915/display/intel_psr.c
> > > > > +++ b/drivers/gpu/drm/i915/display/intel_psr.c
> > > > > @@ -1060,34 +1060,23 @@ static bool
> > > > > psr_interrupt_error_check(struct
> > > > > intel_dp *intel_dp)
> > > > >         return true;
> > > > >  }
> > > > >  
> > > > > -static void intel_psr_enable_locked(struct intel_dp *intel_dp,
> > > > > -                                   const struct intel_crtc_state
> > > > > *crtc_state,
> > > > > -                                   const struct
> > > > > drm_connector_state
> > > > > *conn_state)
> > > > > +static void _intel_psr_enable_locked(struct intel_dp *intel_dp,
> > > > > +                                    const struct
> > > > > intel_crtc_state
> > > > > *crtc_state)
> > > > >  {
> > > > >         struct intel_digital_port *dig_port =
> > > > > dp_to_dig_port(intel_dp);
> > > > >         struct drm_i915_private *dev_priv = dp_to_i915(intel_dp);
> > > > >         struct intel_encoder *encoder = &dig_port->base;
> > > > > -       u32 val;
> > > > >  
> > > > >         drm_WARN_ON(&dev_priv->drm, intel_dp->psr.enabled);
> > > > >  
> > > > > -       intel_dp->psr.psr2_enabled = crtc_state->has_psr2;
> > > > >         intel_dp->psr.busy_frontbuffer_bits = 0;
> > > > > -       intel_dp->psr.pipe = to_intel_crtc(crtc_state-
> > > > > > uapi.crtc)-
> > > > > > pipe;
> > > > > -       intel_dp->psr.transcoder = crtc_state->cpu_transcoder;
> > > > > -       /* DC5/DC6 requires at least 6 idle frames */
> > > > > -       val =
> > > > > usecs_to_jiffies(intel_get_frame_time_us(crtc_state) *
> > > > > 6);
> > > > > -       intel_dp->psr.dc3co_exit_delay = val;
> > > > > -       intel_dp->psr.dc3co_exitline = crtc_state-
> > > > > > dc3co_exitline;
> > > > > -       intel_dp->psr.psr2_sel_fetch_enabled = crtc_state-
> > > > > > enable_psr2_sel_fetch;
> > > > >  
> > > > >         if (!psr_interrupt_error_check(intel_dp))
> > > > >                 return;
> > > > >  
> > > > >         drm_dbg_kms(&dev_priv->drm, "Enabling PSR%s\n",
> > > > >                     intel_dp->psr.psr2_enabled ? "2" : "1");
> > > > > -       intel_dp_compute_psr_vsc_sdp(intel_dp, crtc_state,
> > > > > conn_state,
> > > > > -                                    &intel_dp->psr.vsc);
> > > > > +
> > > > >         intel_write_dp_vsc_sdp(encoder, crtc_state, &intel_dp-
> > > > > > psr.vsc);
> > > > >         intel_psr_enable_sink(intel_dp);
> > > > >         intel_psr_enable_source(intel_dp);
> > > > > @@ -1096,6 +1085,28 @@ static void intel_psr_enable_locked(struct
> > > > > intel_dp *intel_dp,
> > > > >         intel_psr_activate(intel_dp);
> > > > >  }
> > > > >  
> > > > > +static void intel_psr_enable_locked(struct intel_dp *intel_dp,
> > > > > +                                   const struct intel_crtc_state
> > > > > *crtc_state,
> > > > > +                                   const struct
> > > > > drm_connector_state
> > > > > *conn_state)
> > > > > +{
> > > > > +       u32 val;
> > > > > +
> > > > > +       intel_dp->psr.psr2_enabled = crtc_state->has_psr2;
> > > > > +       intel_dp->psr.pipe = to_intel_crtc(crtc_state-
> > > > > > uapi.crtc)-
> > > > > > pipe;
> > > > > +       intel_dp->psr.transcoder = crtc_state->cpu_transcoder;
> > > > > +       /* DC5/DC6 requires at least 6 idle frames */
> > > > > +       val =
> > > > > usecs_to_jiffies(intel_get_frame_time_us(crtc_state) *
> > > > > 6);
> > > > > +       intel_dp->psr.dc3co_exit_delay = val;
> > > > > +       intel_dp->psr.psr2_sel_fetch_enabled = crtc_state-
> > > > > > enable_psr2_sel_fetch;
> > > > > +       intel_dp->psr.dc3co_exitline = crtc_state-
> > > > > > dc3co_exitline;
> > > > > +       intel_dp->psr.paused = false;
> > > > > +
> > > > > +       intel_dp_compute_psr_vsc_sdp(intel_dp, crtc_state,
> > > > > conn_state,
> > > > > +                                    &intel_dp->psr.vsc);
> > > > > +
> > > > > +       _intel_psr_enable_locked(intel_dp, crtc_state);
> > > > > +}
> > > > > +
> > > > >  /**
> > > > >   * intel_psr_enable - Enable PSR
> > > > >   * @intel_dp: Intel DP
> > > > > @@ -1233,6 +1244,60 @@ void intel_psr_disable(struct intel_dp
> > > > > *intel_dp,
> > > > >         cancel_delayed_work_sync(&intel_dp->psr.dc3co_work);
> > > > >  }
> > > > >  
> > > > > +/**
> > > > > + * intel_psr_pause - Pause PSR
> > > > > + * @intel_dp: Intel DP
> > > > > + *
> > > > > + * This function need to be called after enabling psr.
> > > > > + */
> > > > > +void intel_psr_pause(struct intel_dp *intel_dp)
> > > > > +{
> > > > > +       struct intel_psr *psr = &intel_dp->psr;
> > > > > +
> > > > > +       if (!CAN_PSR(intel_dp))
> > > > > +               return;
> > > > > +
> > > > > +       mutex_lock(&psr->lock);
> > > > > +
> > > > > +       if (!psr->active) {
> > > > > +               mutex_unlock(&psr->lock);
> > > > > +               return;
> > > > > +       }
> > > > > +
> > > > > +       intel_psr_exit(intel_dp);
> > > > > +       psr->paused = true;
> > > > > +
> > > > > +       mutex_unlock(&psr->lock);
> > > > > +
> > > > > +       cancel_work_sync(&psr->work);
> > > > > +       cancel_delayed_work_sync(&psr->dc3co_work);
> > > > > +}
> > > > > +
> > > > > +/**
> > > > > + * intel_psr_resume - Resume PSR
> > > > > + * @intel_dp: Intel DP
> > > > > + *
> > > > > + * This function need to be called after pausing psr.
> > > > > + */
> > > > > +void intel_psr_resume(struct intel_dp *intel_dp)
> > > > > +{
> > > > > +       struct intel_psr *psr = &intel_dp->psr;
> > > > > +
> > > > > +       if (!CAN_PSR(intel_dp))
> > > > > +               return;
> > > > > +
> > > > > +       mutex_lock(&psr->lock);
> > > > > +
> > > > > +       if (!psr->paused)
> > > > > +               goto unlock;
> > > > > +
> > > > > +       psr->paused = false;
> > > > > +       intel_psr_activate(intel_dp);
> > > > 
> > > > This patch is doing a bunch of changes around the intel_psr_enable
> > > > but
> > > > then it is calling intel_psr_activate().
> > > > 
> > > > > +
> > > > > +unlock:
> > > > > +       mutex_unlock(&psr->lock);
> > > > > +}
> > > > > +
> > > > >  static void psr_force_hw_tracking_exit(struct intel_dp
> > > > > *intel_dp)
> > > > >  {
> > > > >         struct drm_i915_private *dev_priv = dp_to_i915(intel_dp);
> > > > > diff --git a/drivers/gpu/drm/i915/display/intel_psr.h
> > > > > b/drivers/gpu/drm/i915/display/intel_psr.h
> > > > > index e3db85e97f4c..641521b101c8 100644
> > > > > --- a/drivers/gpu/drm/i915/display/intel_psr.h
> > > > > +++ b/drivers/gpu/drm/i915/display/intel_psr.h
> > > > > @@ -51,5 +51,7 @@ void intel_psr2_program_plane_sel_fetch(struct
> > > > > intel_plane *plane,
> > > > >                                         const struct
> > > > > intel_crtc_state
> > > > > *crtc_state,
> > > > >                                         const struct
> > > > > intel_plane_state *plane_state,
> > > > >                                         int color_plane);
> > > > > +void intel_psr_pause(struct intel_dp *intel_dp);
> > > > > +void intel_psr_resume(struct intel_dp *intel_dp);
> > > > >  
> > > > >  #endif /* __INTEL_PSR_H__ */
> > > > 
> > > 
> > 
> 

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