Re: [PATCH v4 4/5] drm/i915/display: Implement HOBL

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On Thu, 2020-07-09 at 17:24 +0300, Ville Syrjälä wrote:
> On Wed, Jul 08, 2020 at 01:55:11PM -0700, José Roberto de Souza wrote:
> > Hours Of Battery Life is a new GEN12+ power-saving feature that allows
> > supported motherboards to use a special voltage swing table for eDP
> > panels that uses less power.
> > 
> > So here if supported by HW, OEM will set it in VBT and i915 will try
> > to train link with HOBL vswing table if link training fails it fall
> > back to the original table.
> > 
> > intel_ddi_dp_preemph_max() was optimized to only check the HOBL flag
> > instead of do something like is done in intel_ddi_dp_voltage_max()
> > because it is only called after the first entry of the voltage swing
> > table was loaded so the HOBL flag is valid at that point.
> > 
> > v3:
> > - removed a few parameters of icl_ddi_combo_vswing_program() that
> > can be taken from encoder(TODO)
> > 
> > v4:
> > - using the HOBL vswing table until training fails completely (Ville)
> > 
> > BSpec: 49291
> > BSpec: 49399
> > Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> > Cc: Animesh Manna <animesh.manna@xxxxxxxxx>
> > Cc: Manasi Navare <manasi.d.navare@xxxxxxxxx>
> > Signed-off-by: José Roberto de Souza <jose.souza@xxxxxxxxx>
> > ---
> >  drivers/gpu/drm/i915/display/intel_ddi.c      | 37 ++++++++++++++++---
> >  .../drm/i915/display/intel_display_types.h    |  2 +
> >  .../drm/i915/display/intel_dp_link_training.c |  5 +++
> >  drivers/gpu/drm/i915/i915_reg.h               |  2 +
> >  4 files changed, 41 insertions(+), 5 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/display/intel_ddi.c b/drivers/gpu/drm/i915/display/intel_ddi.c
> > index 2c484b55bcdf..bf86c588f726 100644
> > --- a/drivers/gpu/drm/i915/display/intel_ddi.c
> > +++ b/drivers/gpu/drm/i915/display/intel_ddi.c
> > @@ -706,6 +706,15 @@ static const struct cnl_ddi_buf_trans tgl_combo_phy_ddi_translations_dp_hbr2[] =
> >  	{ 0x6, 0x7F, 0x3F, 0x00, 0x00 },	/* 900   900      0.0   */
> >  };
> >  
> > +static const struct cnl_ddi_buf_trans tgl_combo_phy_ddi_translations_edp_hbr2_hobl[] = {
> > +	{ 0x6, 0x7F, 0x3F, 0x00, 0x00 }
> > +};
> > +
> > +static bool is_hobl_buf_trans(const struct cnl_ddi_buf_trans *table)
> > +{
> > +	return table == tgl_combo_phy_ddi_translations_edp_hbr2_hobl;
> > +}
> > +
> >  static const struct ddi_buf_trans *
> >  bdw_get_buf_trans_edp(struct intel_encoder *encoder, int *n_entries)
> >  {
> > @@ -1050,6 +1059,16 @@ static const struct cnl_ddi_buf_trans *
> >  tgl_get_combo_buf_trans(struct intel_encoder *encoder, int type, int rate,
> >  			int *n_entries)
> >  {
> > +	if (type == INTEL_OUTPUT_EDP && dev_priv->vbt.edp.hobl) {
> > +		struct intel_dp *intel_dp = enc_to_intel_dp(encoder);
> > +
> > +		if (!intel_dp->hobl_disabled && rate <= 540000) {
> > +			/* Same table applies to TGL, RKL and DG1 */
> > +			*n_entries = ARRAY_SIZE(tgl_combo_phy_ddi_translations_edp_hbr2_hobl);
> > +			return tgl_combo_phy_ddi_translations_edp_hbr2_hobl;
> > +		}
> > +	}
> > +
> >  	if (type == INTEL_OUTPUT_HDMI || type == INTEL_OUTPUT_EDP) {
> >  		return icl_get_combo_buf_trans(encoder, type, rate, n_entries);
> >  	} else if (rate > 270000) {
> > @@ -2223,13 +2242,12 @@ static u8 intel_ddi_dp_voltage_max(struct intel_dp *intel_dp)
> >  		DP_TRAIN_VOLTAGE_SWING_MASK;
> >  }
> >  
> > -/*
> > - * We assume that the full set of pre-emphasis values can be
> > - * used on all DDI platforms. Should that change we need to
> > - * rethink this code.
> > - */
> >  static u8 intel_ddi_dp_preemph_max(struct intel_dp *intel_dp)
> >  {
> > +	/* HOBL voltage swing table only have one entry */
> > +	if (intel_dp->hobl_active)
> > +		return DP_TRAIN_PRE_EMPH_LEVEL_0;
> 
> That's illegal. We need to claim support for at least all
> vswing/pre-emphasis levels 0-2. 3 is optional. Though there is
> some confusion around this in the eDP spec where it kinda seems suggest
> that even some of the level 2 things are optional. But it's so unclear
> I would defer to just trusting what the DP spec says.

Okay so in this case I should add more entries to tgl_combo_phy_ddi_translations_edp_hbr2_hobl with the same values to match the minimum required by
DP spec?

> 
> /me goes to write the patch with the WARNs...

Will take a look.

> 
> 
> > +
> >  	return DP_TRAIN_PRE_EMPH_LEVEL_3;
> >  }
> >  
> > @@ -2392,6 +2410,15 @@ static void icl_ddi_combo_vswing_program(struct intel_encoder *encoder,
> >  		level = n_entries - 1;
> >  	}
> >  
> > +	if (INTEL_GEN(dev_priv) >= 12 && type == INTEL_OUTPUT_EDP) {
> > +		struct intel_dp *intel_dp = enc_to_intel_dp(encoder);
> > +
> > +		val = EDP4K2K_MODE_OVRD_EN | EDP4K2K_MODE_OVRD_OPTIMIZED;
> > +		intel_dp->hobl_active = is_hobl_buf_trans(ddi_translations);
> > +		intel_de_rmw(dev_priv, ICL_PORT_CL_DW10(phy), val,
> > +			     intel_dp->hobl_active ? val : 0);
> > +	}
> 
> I'd still suggest writing that unconditionally.

Okay

> 
> > +
> >  	/* Set PORT_TX_DW5 */
> >  	val = intel_de_read(dev_priv, ICL_PORT_TX_DW5_LN0(phy));
> >  	val &= ~(SCALING_MODE_SEL_MASK | RTERM_SELECT_MASK |
> > diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h b/drivers/gpu/drm/i915/display/intel_display_types.h
> > index e8f809161c75..fd4f0e4d0be7 100644
> > --- a/drivers/gpu/drm/i915/display/intel_display_types.h
> > +++ b/drivers/gpu/drm/i915/display/intel_display_types.h
> > @@ -1375,6 +1375,8 @@ struct intel_dp {
> >  
> >  	/* Display stream compression testing */
> >  	bool force_dsc_en;
> > +
> > +	u8 hobl_disabled : 1, hobl_active : 1, hobl_not_used : 6;
> 
> Why did we go from a simple boolean to this complicated thing?

Will try to remove one.

> 
> >  };
> >  
> >  enum lspcon_vendor {
> > diff --git a/drivers/gpu/drm/i915/display/intel_dp_link_training.c b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
> > index 2493142a70e9..925822fd386d 100644
> > --- a/drivers/gpu/drm/i915/display/intel_dp_link_training.c
> > +++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
> > @@ -401,6 +401,11 @@ intel_dp_start_link_train(struct intel_dp *intel_dp)
> >  		    intel_connector->base.base.id,
> >  		    intel_connector->base.name,
> >  		    intel_dp->link_rate, intel_dp->lane_count);
> > +	if (intel_dp->hobl_active) {
> > +		drm_dbg_kms(&dp_to_i915(intel_dp)->drm,
> > +			    "Link Training failed with HOBL active, not enabling it for now on");
> > +		intel_dp->hobl_disabled = true;
> 
> I don't think we should do the link rate/lanes reduction in
> this case. Ie. we should just mark hobl as no good and retry
> the link training with the same link param limits.

Okay

> 
> > +	}
> >  	if (!intel_dp_get_link_train_fallback_values(intel_dp,
> >  						     intel_dp->link_rate,
> >  						     intel_dp->lane_count))
> > diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> > index 86a23ced051b..ea16931c0fa4 100644
> > --- a/drivers/gpu/drm/i915/i915_reg.h
> > +++ b/drivers/gpu/drm/i915/i915_reg.h
> > @@ -1898,6 +1898,8 @@ static inline bool i915_mmio_reg_valid(i915_reg_t reg)
> >  #define  PWR_DOWN_LN_3_1_0		(0xb << 4)
> >  #define  PWR_DOWN_LN_MASK		(0xf << 4)
> >  #define  PWR_DOWN_LN_SHIFT		4
> > +#define  EDP4K2K_MODE_OVRD_EN		(1 << 3)
> > +#define  EDP4K2K_MODE_OVRD_OPTIMIZED	(1 << 2)
> >  
> >  #define ICL_PORT_CL_DW12(phy)		_MMIO(_ICL_PORT_CL_DW(12, phy))
> >  #define   ICL_LANE_ENABLE_AUX		(1 << 0)
> > -- 
> > 2.27.0
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