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

["Almahallawy, Khaled" <khaled.almahallawy@intel.com>]

On Tue, 2021-10-19 at 15:01 +0300, Ville Syrjälä wrote:
> On Tue, Oct 19, 2021 at 02:52:15PM +0300, Jani Nikula wrote:
> > On Mon, 19 Jul 2021, Khaled Almahallawy <
> > khaled.almahallawy@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.

The  intention for this patch is to call “intel_dp->set_link_train”
inside “intel_dp_phy_pattern_update” when adding CP2520_PAT3/TPS4
instead of following this approach: 
https://patchwork.freedesktop.org/patch/378522/ 
 
Unfortunately, the only way to set TPS4 is through DP_TP_CTL unlike the
rest of PHY test patterns in DP_COMP_CTL(specs:50482) 
 
Could you please suggest what is the recommended way to add the support
of TPS4 PHY pattern to compliance code?

Thank you
Khaled
> 
> > BR,
> > Jani.
> > 
> > > Cc: Manasi Navare <manasi.d.navare@intel.com>
> > > Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > > CC: José Roberto de Souza <jose.souza@intel.com>
> > > Cc: Imre Deak <imre.deak@intel.com>
> > > Signed-off-by: Khaled Almahallawy <khaled.almahallawy@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