Re: [Intel-gfx] [PATCH v27 2/6] drm/i915: Separate icl and skl SAGV checking

["Lisovskiy, Stanislav" <stanislav.lisovskiy@intel.com>]

On Tue, May 05, 2020 at 01:42:46PM +0300, Ville Syrjälä wrote:
> On Tue, May 05, 2020 at 01:22:43PM +0300, Stanislav Lisovskiy wrote:
> > Introduce platform dependent SAGV checking in
> > combination with bandwidth state pipe SAGV mask.
> > 
> > v2, v3, v4, v5, v6: Fix rebase conflict
> > 
> > Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
> > ---
> >  drivers/gpu/drm/i915/intel_pm.c | 30 ++++++++++++++++++++++++++++--
> >  1 file changed, 28 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> > index da567fac7c93..c7d726a656b2 100644
> > --- a/drivers/gpu/drm/i915/intel_pm.c
> > +++ b/drivers/gpu/drm/i915/intel_pm.c
> > @@ -3853,6 +3853,24 @@ static bool intel_crtc_can_enable_sagv(const struct intel_crtc_state *crtc_state
> >  	return true;
> >  }
> >  
> > +static bool skl_crtc_can_enable_sagv(const struct intel_crtc_state *crtc_state)
> > +{
> > +	struct intel_atomic_state *state = to_intel_atomic_state(crtc_state->uapi.state);
> > +	/*
> > +	 * SKL+ workaround: bspec recommends we disable SAGV when we have
> > +	 * more then one pipe enabled
> > +	 */
> > +	if (hweight8(state->active_pipes) > 1)
> > +		return false;
> 
> That stuff should no longer be here since we now have it done properly
> in intel_can_eanble_sagv().
> 
> > +
> > +	return intel_crtc_can_enable_sagv(crtc_state);
> > +}
> > +
> > +static bool icl_crtc_can_enable_sagv(const struct intel_crtc_state *crtc_state)
> > +{
> > +	return intel_crtc_can_enable_sagv(crtc_state);
> > +}
> 
> This looks the wrong way around. IMO intel_crtc_can_enable_sagv()
> should rather call the skl vs. icl variants as needed. Although we
> don't yet have the icl variant so the oerdering of the patches is
> a bit weird.

This is done so, because icl and skl checking share the same code
to check if SAGV can be enabled, except active_pipes > 1 thing.

So that icl and skl can share the same code avoiding duplicating,
i.e if I put code from intel_crtc_can_enable_sagv to 
skl_crtc_can_enable_sagv, I will have to 
1) either duplicate this code to icl_crtc_can_enable_sagv(if I add remaining active_pipes check to
skl)
2) use skl_crtc_can_enable_sagv from icl_crtc_can_enable_sagv,
but this active_pipes check will be still outside of this skl function,
which I don't find nice - to me the best way is to keep all skl
specific checks in a correspondent function.

So that is why I preferred to extract some common code to some separate
universal function which can be then used from both icl and skl functions:
from icl it is used "as is" and from skl it is intel_crtc_can_enable_sagv
+ this active_pipes check.

Currently anyway we of course have that active_pipes check in intel_can_enable_sagv
i.e already outside of skl_crtc_can_enable_sagv(where it should be imo),
so was your intention to leave it outside anyway?

Stan

> 
> > +
> >  bool intel_can_enable_sagv(const struct intel_bw_state *bw_state)
> >  {
> >  	if (bw_state->active_pipes && !is_power_of_2(bw_state->active_pipes))
> > @@ -3863,22 +3881,30 @@ bool intel_can_enable_sagv(const struct intel_bw_state *bw_state)
> >  
> >  static int intel_compute_sagv_mask(struct intel_atomic_state *state)
> >  {
> > +	struct drm_i915_private *dev_priv = to_i915(state->base.dev);
> >  	int ret;
> >  	struct intel_crtc *crtc;
> > -	struct intel_crtc_state *new_crtc_state;
> > +	const struct intel_crtc_state *new_crtc_state;
> >  	struct intel_bw_state *new_bw_state = NULL;
> >  	const struct intel_bw_state *old_bw_state = NULL;
> >  	int i;
> >  
> >  	for_each_new_intel_crtc_in_state(state, crtc,
> >  					 new_crtc_state, i) {
> > +		bool can_sagv;
> > +
> >  		new_bw_state = intel_atomic_get_bw_state(state);
> >  		if (IS_ERR(new_bw_state))
> >  			return PTR_ERR(new_bw_state);
> >  
> >  		old_bw_state = intel_atomic_get_old_bw_state(state);
> >  
> > -		if (intel_crtc_can_enable_sagv(new_crtc_state))
> > +		if (INTEL_GEN(dev_priv) >= 11)
> > +			can_sagv = icl_crtc_can_enable_sagv(new_crtc_state);
> > +		else
> > +			can_sagv = skl_crtc_can_enable_sagv(new_crtc_state);
> > +
> > +		if (can_sagv)
> >  			new_bw_state->pipe_sagv_reject &= ~BIT(crtc->pipe);
> >  		else
> >  			new_bw_state->pipe_sagv_reject |= BIT(crtc->pipe);
> > -- 
> > 2.24.1.485.gad05a3d8e5
> 
> -- 
> Ville Syrjälä
> Intel
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