[PATCHv4] drm/i915/dp: Guarantee a minimum HBlank time

[Murthy, Arun R]

> > -----Original Message-----
> > From: Intel-xe <intel-xe-bounces at lists.freedesktop.org> On Behalf Of
> > Arun R Murthy
> > Sent: Monday, November 11, 2024 2:56 PM
> > To: intel-xe at lists.freedesktop.org; intel-gfx at lists.freedesktop.org
> > Cc: Murthy, Arun R <arun.r.murthy at intel.com>
> > Subject: [PATCHv4] drm/i915/dp: Guarantee a minimum HBlank time
> >
> > Mandate a minimum Hblank symbol cycle count between BS and BE in
> > 8b/10b MST and 12b/132b mode.
> 
> Missed the typo here *128
> 
> > Spec: DP2.1a
> >
> > v2: Affine calculation/updation of min HBlank to dp_mst (Jani)
> > v3: moved min_hblank from struct intel_dp to intel_crtc_state (Jani)
> > v4: use max/min functions, change intel_xx *intel_xx to intel_xx *xx
> >     (Jani)
> >     Limit hblank to 511 and accomodate BS/BE in calculated value
> >     (Srikanth)
> >
> > Signed-off-by: Arun R Murthy <arun.r.murthy at intel.com>
> > ---
> >  .../drm/i915/display/intel_crtc_state_dump.c  |  1 +
> >  .../drm/i915/display/intel_display_types.h    |  1 +
> >  drivers/gpu/drm/i915/display/intel_dp_mst.c   | 35 +++++++++++++++++++
> >  drivers/gpu/drm/i915/i915_reg.h               |  4 +++
> >  4 files changed, 41 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/i915/display/intel_crtc_state_dump.c
> > b/drivers/gpu/drm/i915/display/intel_crtc_state_dump.c
> > index 705ec5ad385c..f8c1d1dd66a3 100644
> > --- a/drivers/gpu/drm/i915/display/intel_crtc_state_dump.c
> > +++ b/drivers/gpu/drm/i915/display/intel_crtc_state_dump.c
> > @@ -258,6 +258,7 @@ void intel_crtc_state_dump(const struct
> > intel_crtc_state *pipe_config,
> >  			   str_enabled_disabled(pipe_config-
> > >has_sel_update),
> >  			   str_enabled_disabled(pipe_config-
> > >has_panel_replay),
> >  			   str_enabled_disabled(pipe_config-
> > >enable_psr2_sel_fetch));
> > +		drm_printf(&p, "minimum HBlank: %d\n", pipe_config-
> > >min_hblank);
> >  	}
> 
> Covers the dump but still missing the checker Also maybe a different patch for
> this work
> 
Checker may not be required alike max_link_bpp_x16 since this a must on every modeset.

> >
> >  	drm_printf(&p, "framestart delay: %d, MSA timing delay: %d\n", diff
> > -- git a/drivers/gpu/drm/i915/display/intel_display_types.h
> > b/drivers/gpu/drm/i915/display/intel_display_types.h
> > index d3a1aa7c919f..d2716addf88e 100644
> > --- a/drivers/gpu/drm/i915/display/intel_display_types.h
> > +++ b/drivers/gpu/drm/i915/display/intel_display_types.h
> > @@ -1075,6 +1075,7 @@ struct intel_crtc_state {
> >
> >  	int max_link_bpp_x16;	/* in 1/16 bpp units */
> >  	int pipe_bpp;		/* in 1 bpp units */
> > +	int min_hblank;		/* min HBlank for DP2.1 */
> 
> Is it only for DP2.1 because we end up filling in both cases if uhbr or not just
> with different values
> 
Its for only MST case applicable for both uhbr and non-uhbr rates. The minimum calculation values changes based on uhbr/non-uhbr rates.

Thanks and Regards,
Arun R Murthy
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