[Intel-gfx] [PATCH] drm/i915/dp: Add missing TPS4 programming bits

[Ville Syrjälä]

On Tue, Oct 19, 2021 at 02:52:15PM +0300, Jani Nikula wrote:
> On Mon, 19 Jul 2021, Khaled Almahallawy <khaled.almahallawy at intel.com> wrote:
> > Bits 20:19 are used to set CP2520 Patterns 1/2/3 (refer to Specs:50484).
> > TPS4 is CP2520 Pattern 3 (refer to DP2.0 spaces Table 3-11, DPCD 00248h
> > LINK_QUAL_PATTERN_SELECT, and DP PHY 1.4 CTS - Appendix A - Compliance
> > EYE Pattern(CP2520; Normative))
> >
> > For TPS4, setting bits 20:19 to value != 00b, leads to a non-TPS4 pattern.
> > This is confirmed using DP Scope running DP1.4 PHY CTS.
> >
> > To avoid any accidental wrong setting of bits 20:19, set it correctly for
> > TPS4 LT pattern selection. This programming sequence is the same used by EV.
> 
> Do we need this?

I think what we need is some place to initialize DP_TP_CTL fully.
Right now it seems to be just all RMW.

> 
> BR,
> Jani.
> 
> >
> > Cc: Manasi Navare <manasi.d.navare at intel.com>
> > Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > CC: José Roberto de Souza <jose.souza at intel.com>
> > Cc: Imre Deak <imre.deak at intel.com>
> > Signed-off-by: Khaled Almahallawy <khaled.almahallawy at intel.com>
> > ---
> >  drivers/gpu/drm/i915/display/intel_ddi.c | 2 ++
> >  drivers/gpu/drm/i915/i915_reg.h          | 4 ++++
> >  2 files changed, 6 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/i915/display/intel_ddi.c b/drivers/gpu/drm/i915/display/intel_ddi.c
> > index 26a3aa73fcc4..54b4b28fdc74 100644
> > --- a/drivers/gpu/drm/i915/display/intel_ddi.c
> > +++ b/drivers/gpu/drm/i915/display/intel_ddi.c
> > @@ -3412,6 +3412,8 @@ static void intel_ddi_set_link_train(struct intel_dp *intel_dp,
> >  		break;
> >  	case DP_TRAINING_PATTERN_4:
> >  		temp |= DP_TP_CTL_LINK_TRAIN_PAT4;
> > +		temp &= ~DP_TP_CTL_TRAIN_PAT4_SEL_MASK;
> > +		temp |= DP_TP_CTL_TRAIN_PAT4_SEL_TP4a;
> >  		break;
> >  	}
> >  
> > diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> > index 943fe485c662..a65998df9994 100644
> > --- a/drivers/gpu/drm/i915/i915_reg.h
> > +++ b/drivers/gpu/drm/i915/i915_reg.h
> > @@ -10176,6 +10176,10 @@ enum skl_power_gate {
> >  #define  DP_TP_CTL_MODE_SST			(0 << 27)
> >  #define  DP_TP_CTL_MODE_MST			(1 << 27)
> >  #define  DP_TP_CTL_FORCE_ACT			(1 << 25)
> > +#define  DP_TP_CTL_TRAIN_PAT4_SEL_MASK		(3 << 19)
> > +#define  DP_TP_CTL_TRAIN_PAT4_SEL_TP4a		(0 << 19)
> > +#define  DP_TP_CTL_TRAIN_PAT4_SEL_TP4b		(1 << 19)
> > +#define  DP_TP_CTL_TRAIN_PAT4_SEL_TP4c		(2 << 19)
> >  #define  DP_TP_CTL_ENHANCED_FRAME_ENABLE	(1 << 18)
> >  #define  DP_TP_CTL_FDI_AUTOTRAIN		(1 << 15)
> >  #define  DP_TP_CTL_LINK_TRAIN_MASK		(7 << 8)
> 
> -- 
> Jani Nikula, Intel Open Source Graphics Center

-- 
Ville Syrjälä
Intel