[PATCH v4 4/5] drm/i915/psr: Add IO buffer wake times for LunarLake and beyond

[Hogander, Jouni]

On Thu, 2024-03-07 at 19:15 +0200, Ville Syrjälä wrote:
> On Wed, Mar 06, 2024 at 10:34:26AM +0200, Jouni Högander wrote:
> > IO buffer wake time used for IO wake calculation is dependent on
> > port clock
> > on LunarLake and beyond. Take this into account in
> > get_io_buffer_wake_time.
> > 
> > Bspec: 65450
> > 
> > Signed-off-by: Jouni Högander <jouni.hogander at intel.com>
> > ---
> >  drivers/gpu/drm/i915/display/intel_psr.c | 9 ++++++++-
> >  1 file changed, 8 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/display/intel_psr.c
> > b/drivers/gpu/drm/i915/display/intel_psr.c
> > index e1df0ece9fa3..e8410e770da8 100644
> > --- a/drivers/gpu/drm/i915/display/intel_psr.c
> > +++ b/drivers/gpu/drm/i915/display/intel_psr.c
> > @@ -1160,6 +1160,9 @@ static bool _lnl_compute_alpm_params(struct
> > intel_dp *intel_dp,
> >   * This is not directly mentioned in Bspec. There are 50 us io
> > wake time and 32
> >   * us fast wake time. Clearly preharge pulses are not (improperly)
> > included in
> >   * 32 us fast wake time. 50 us - 32 us = 18 us.
> > + *
> > + * For DISPLAY_VER >= 20
> > + * RBR 15us, HBR1 11us, higher rates 10us
> >   */
> >  static int get_io_buffer_wake_time(const struct intel_crtc_state
> > *crtc_state)
> >  {
> > @@ -1167,8 +1170,12 @@ static int get_io_buffer_wake_time(const
> > struct intel_crtc_state *crtc_state)
> >  
> >         if (DISPLAY_VER(i915) < 12)
> >                 return 18;
> > -       else
> > +       else if (DISPLAY_VER(i915) < 20 || crtc_state->port_clock >
> > 270000)
> >                 return 10;
> > +       else if (crtc_state->port_clock > 162000)
> > +               return 11;
> > +       else
> > +               return 15;
> 
> That's getting rather messy. I think having separate functions for 
> skl vs. tgl vs. mtl (assuming the ver==20 is mtl) would be cleaner.

ver == 20 == lnl
ver == 14 == mtl

So you are thinking get_io_buffer_wake_time would do:

 	if (DISPLAY_VER(i915) >= 20)
 		lnl_get_io_buffer_wake_time();
	else if (DISPLAY_VER(i915) >= 12)
                tgl_get_io_buffer_wake_time();
        else
		skl_get_buffer_wake_time();

?

BR,

Jouni Högander

> And the only one of those that I think deserves a comment is skl
> since 
> there we don't get a proper value from bspec directly.
> 
> >  }
> >  
> >  static bool _compute_alpm_params(struct intel_dp *intel_dp,
> > -- 
> > 2.34.1
>