Re: [PATCH 10/14] drm/i915/dsb: Introduce intel_dsb_chain()

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Wed, Jul 03, 2024 at 12:10:38PM +0000, Manna, Animesh wrote:
> 
> 
> > -----Original Message-----
> > From: Intel-gfx <intel-gfx-bounces@lists.freedesktop.org> On Behalf Of Ville
> > Syrjala
> > Sent: Tuesday, June 25, 2024 12:40 AM
> > To: intel-gfx@lists.freedesktop.org
> > Subject: [PATCH 10/14] drm/i915/dsb: Introduce intel_dsb_chain()
> > 
> > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > 
> > In order to handle the DEwake tricks without involving the CPU we need a
> > mechanism by which one DSB can start another one. Add a basic function to
> > do so. We'll extend it later with additional code to actually deal with DEwake.
> 
> Is chained DSB concept restricting to only 2 DSB instance or can be extended to available/max DSB instances? 
> 
> Are we exposing full chain of DSB to user or can be restrict to primary DSB which will control other instances?

You can start any DSB from any other DSB.

> > 
> > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > ---
> >  drivers/gpu/drm/i915/display/intel_dsb.c | 42 ++++++++++++++++++++++++
> > drivers/gpu/drm/i915/display/intel_dsb.h |  3 ++
> >  2 files changed, 45 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/i915/display/intel_dsb.c
> > b/drivers/gpu/drm/i915/display/intel_dsb.c
> > index 092cf082ac39..4c0519c41f16 100644
> > --- a/drivers/gpu/drm/i915/display/intel_dsb.c
> > +++ b/drivers/gpu/drm/i915/display/intel_dsb.c
> > @@ -502,6 +502,48 @@ static u32 dsb_error_int_en(struct intel_display
> > *display)
> >  	return errors;
> >  }
> > 
> > +static void _intel_dsb_chain(struct intel_atomic_state *state,
> > +			     struct intel_dsb *dsb,
> > +			     struct intel_dsb *chained_dsb,
> > +			     u32 ctrl)
> 
> I do not see any usage of ctrl variable in this patch, maybe good to add wherever will be using it.

It's in the next patch.

> 
> Regards,
> Animesh
> > +{
> > +	struct intel_display *display = to_intel_display(state->base.dev);
> > +	struct intel_crtc *crtc = dsb->crtc;
> > +	enum pipe pipe = crtc->pipe;
> > +	u32 tail;
> > +
> > +	if (drm_WARN_ON(display->drm, dsb->id == chained_dsb->id))
> > +		return;
> > +
> > +	tail = chained_dsb->free_pos * 4;
> > +	if (drm_WARN_ON(display->drm, !IS_ALIGNED(tail,
> > CACHELINE_BYTES)))
> > +		return;
> > +
> > +	intel_dsb_reg_write(dsb, DSB_CTRL(pipe, chained_dsb->id),
> > +			    ctrl | DSB_ENABLE);
> > +
> > +	intel_dsb_reg_write(dsb, DSB_CHICKEN(pipe, chained_dsb->id),
> > +			    dsb_chicken(state, crtc));
> > +
> > +	intel_dsb_reg_write(dsb, DSB_INTERRUPT(pipe, chained_dsb->id),
> > +			    dsb_error_int_status(display) |
> > DSB_PROG_INT_STATUS |
> > +			    dsb_error_int_en(display));
> > +
> > +	intel_dsb_reg_write(dsb, DSB_HEAD(pipe, chained_dsb->id),
> > +			    intel_dsb_buffer_ggtt_offset(&chained_dsb-
> > >dsb_buf));
> > +
> > +	intel_dsb_reg_write(dsb, DSB_TAIL(pipe, chained_dsb->id),
> > +			    intel_dsb_buffer_ggtt_offset(&chained_dsb-
> > >dsb_buf) + tail); }
> > +
> > +void intel_dsb_chain(struct intel_atomic_state *state,
> > +		     struct intel_dsb *dsb,
> > +		     struct intel_dsb *chained_dsb)
> > +{
> > +	_intel_dsb_chain(state, dsb, chained_dsb,
> > +			 0);
> > +}
> > +
> >  static void _intel_dsb_commit(struct intel_dsb *dsb, u32 ctrl,
> >  			      int hw_dewake_scanline)
> >  {
> > diff --git a/drivers/gpu/drm/i915/display/intel_dsb.h
> > b/drivers/gpu/drm/i915/display/intel_dsb.h
> > index d0737cefb393..e59fd7da0fc0 100644
> > --- a/drivers/gpu/drm/i915/display/intel_dsb.h
> > +++ b/drivers/gpu/drm/i915/display/intel_dsb.h
> > @@ -45,6 +45,9 @@ void intel_dsb_wait_scanline_in(struct
> > intel_atomic_state *state,  void intel_dsb_wait_scanline_out(struct
> > intel_atomic_state *state,
> >  				 struct intel_dsb *dsb,
> >  				 int lower, int upper);
> > +void intel_dsb_chain(struct intel_atomic_state *state,
> > +		     struct intel_dsb *dsb,
> > +		     struct intel_dsb *chained_dsb);
> > 
> >  void intel_dsb_commit(struct intel_dsb *dsb,
> >  		      bool wait_for_vblank);
> > --
> > 2.44.2
> 

-- 
Ville Syrjälä
Intel