Re: [PATCH v3 2/9] drm/i915/skl+: use linetime latency instead of ddb size

["Zanoni, Paulo R" <paulo.r.zanoni@intel.com>]

Em Seg, 2016-09-19 às 15:19 -0300, Paulo Zanoni escreveu:
> Em Sex, 2016-09-09 às 13:30 +0530, Kumar, Mahesh escreveu:
> > 
> > From: Mahesh Kumar <mahesh1.kumar@intel.com>
> > 
> > This patch make changes to use linetime latency instead of
> > allocated
> > DDB size during plane watermark calculation in switch case, This is
> > required to implement new DDB allocation algorithm.
> > 
> > In New Algorithm DDB is allocated based on WM values, because of
> > which
> > number of DDB blocks will not be available during WM calculation,
> > So this "linetime latency" is suggested by SV/HW team to use during
> > switch-case for WM blocks selection.
> 
> Why is this not part of BSpec? If there's some problem with the
> current
> algorithm and we need a new one, why is it not part of our spec?
> 
> > 
> > 
> > Changes since v1:
> >  - Rebase on top of Paulo's patch series
> > 
> > Signed-off-by: Mahesh Kumar <mahesh1.kumar@intel.com>
> > ---
> >  drivers/gpu/drm/i915/intel_pm.c | 7 ++++++-
> >  1 file changed, 6 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/intel_pm.c
> > b/drivers/gpu/drm/i915/intel_pm.c
> > index 3fdec4d..cfd9b7d1 100644
> > --- a/drivers/gpu/drm/i915/intel_pm.c
> > +++ b/drivers/gpu/drm/i915/intel_pm.c
> > @@ -3622,10 +3622,15 @@ static int skl_compute_plane_wm(const
> > struct
> > drm_i915_private *dev_priv,
> >  	    fb->modifier[0] == I915_FORMAT_MOD_Yf_TILED) {
> >  		selected_result = max(method2, y_tile_minimum);
> >  	} else {
> > +		uint32_t linetime_us = 0;
> > +
> > +		linetime_us = DIV_ROUND_UP(width * 1000,
> > +				skl_pipe_pixel_rate(cstate));

Also, shouldn't this be width * 8 * 1000?

> > +
> >  		if ((cpp * cstate->base.adjusted_mode.crtc_htotal
> > /
> > 512 < 1) &&
> >  		    (plane_bytes_per_line / 512 < 1))
> >  			selected_result = method2;
> > -		else if ((ddb_allocation / plane_blocks_per_line)
> > >=
> > 1)
> > +		if (latency >= linetime_us)
> >  			selected_result = min(method1, method2);
> >  		else
> >  			selected_result = method1;
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