Re: [Intel-gfx] [PATCH v3 3/4] drm/i915/psr: Check that vblank is long enough for psr2

["Hogander, Jouni" <jouni.hogander@intel.com>]

On Tue, 2023-03-21 at 17:43 +0200, Ville Syrjälä wrote:
> On Mon, Mar 20, 2023 at 06:59:44PM +0200, Jouni Högander wrote:
> > Ensure vblank >= psr2 vblank
> > where
> > Psr2 vblank = PSR2_CTL Block Count Number maximum line count.
> > 
> > Bspec: 71580, 49274
> > 
> > Signed-off-by: Jouni Högander <jouni.hogander@intel.com>
> > ---
> >  drivers/gpu/drm/i915/display/intel_psr.c | 8 ++++++++
> >  1 file changed, 8 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/i915/display/intel_psr.c
> > b/drivers/gpu/drm/i915/display/intel_psr.c
> > index 1050d777a108..1b40d9c73c18 100644
> > --- a/drivers/gpu/drm/i915/display/intel_psr.c
> > +++ b/drivers/gpu/drm/i915/display/intel_psr.c
> > @@ -958,6 +958,14 @@ static bool intel_psr2_config_valid(struct
> > intel_dp *intel_dp,
> >                 return false;
> >         }
> >  
> > +       /* Vblank >= PSR2_CTL Block Count Number maximum line count
> > */
> > +       if (crtc_state->hw.adjusted_mode.crtc_vblank_end -
> > +           crtc_state->hw.adjusted_mode.crtc_vblank_start < 12) {
> 
> Why 12? Shouldn't it be based on the wake_lines/BLOCK_COUNT_NUM
> stuff?

I took this directly from Bspec. I think your suggestions make sense. I
will experiment them and come back on this.

> 
> 
> If so I would suggest we try someting like this:
> 
> psr2_block_count_lines()
> {
>         return ...wake_lines... ? 12 : 8;
> }
> 
> psr2_block_count()
> {
>         return psr2_block_count_lines() / 4;
> }
> 
> if (vblank_lengh < psr2_block_count_lines())
>         fail;
> 
> if (psr_block_count() > 2)
>         val |= BLOCK_COUNT_NUM_3;
> else
>         val |= BLOCK_COUNT_NUM_2;
> 
> > +               drm_dbg_kms(&dev_priv->drm,
> > +                           "PSR2 not enabled, too short vblank
> > time\n");
> > +               return false;
> > +       }
> > +
> >         if (HAS_PSR2_SEL_FETCH(dev_priv)) {
> >                 if (!intel_psr2_sel_fetch_config_valid(intel_dp,
> > crtc_state) &&
> >                     !HAS_PSR_HW_TRACKING(dev_priv)) {
> > -- 
> > 2.34.1
>