Re: [Intel-gfx] [PATCH v5 1/2] drm/i915/display: Implement HOBL

["Souza, Jose" <jose.souza@intel.com>]

On Tue, 2020-07-14 at 19:43 +0300, Ville Syrjälä wrote:
> On Mon, Jul 13, 2020 at 04:53:33PM -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
> > 
> > v4:
> > - using the HOBL vswing table until training fails completely (Ville)
> > 
> > v5:
> > - not reducing lane or link rate when link training fails with HOBL
> > active
> > - duplicated the HOBL voltage swing entry to match DP spec requirement
> > 
> > BSpec: 49291
> > BSpec: 49399
> > Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > Cc: Animesh Manna <animesh.manna@intel.com>
> > Cc: Manasi Navare <manasi.d.navare@intel.com>
> > Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
> > ---
> >  drivers/gpu/drm/i915/display/intel_ddi.c      | 42 +++++++++++++++++++
> >  .../drm/i915/display/intel_display_types.h    |  2 +
> >  .../drm/i915/display/intel_dp_link_training.c | 19 ++++++---
> >  drivers/gpu/drm/i915/i915_reg.h               |  2 +
> >  4 files changed, 59 insertions(+), 6 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/display/intel_ddi.c b/drivers/gpu/drm/i915/display/intel_ddi.c
> > index 2c484b55bcdf..92ae036440fa 100644
> > --- a/drivers/gpu/drm/i915/display/intel_ddi.c
> > +++ b/drivers/gpu/drm/i915/display/intel_ddi.c
> > @@ -706,6 +706,29 @@ static const struct cnl_ddi_buf_trans tgl_combo_phy_ddi_translations_dp_hbr2[] =
> >  	{ 0x6, 0x7F, 0x3F, 0x00, 0x00 },	/* 900   900      0.0   */
> >  };
> >  
> > +/*
> > + * Cloned the HOBL entry to comply with the voltage and pre-emphasis entries
> > + * that DisplayPort specification requires
> > + */
> > +static const struct cnl_ddi_buf_trans tgl_combo_phy_ddi_translations_edp_hbr2_hobl[] = {
> > +						/* VS	pre-emp	*/
> > +	{ 0x6, 0x7F, 0x3F, 0x00, 0x00 },	/* 0	0	*/
> > +	{ 0x6, 0x7F, 0x3F, 0x00, 0x00 },	/* 0	1	*/
> > +	{ 0x6, 0x7F, 0x3F, 0x00, 0x00 },	/* 0	2	*/
> > +	{ 0x6, 0x7F, 0x3F, 0x00, 0x00 },	/* 0	3	*/
> > +	{ 0x6, 0x7F, 0x3F, 0x00, 0x00 },	/* 1	0	*/
> > +	{ 0x6, 0x7F, 0x3F, 0x00, 0x00 },	/* 1	1	*/
> > +	{ 0x6, 0x7F, 0x3F, 0x00, 0x00 },	/* 1	2	*/
> > +	{ 0x6, 0x7F, 0x3F, 0x00, 0x00 },	/* 2	0	*/
> > +	{ 0x6, 0x7F, 0x3F, 0x00, 0x00 },	/* 2	1	*/
> > +	{ 0x6, 0x7F, 0x3F, 0x00, 0x00 },	/* 3	0	*/
> 
> We could skip the last entry since that's still legal. Dunno which is
> better though.
> 
> > +};
> > +
> > +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 +1073,16 @@ 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_failed && 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) {
> > @@ -2392,6 +2425,15 @@ static void icl_ddi_combo_vswing_program(struct intel_encoder *encoder,
> >  		level = n_entries - 1;
> >  	}
> >  
> > +	if (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);
> 
> Still don't understand why we have these two booleans and this table
> comparison. Why not just set the intel_dp->hobl=true intiailly
> based on vbt, and clear it if and when link training fails?

Because HOBL is not compatible with HBR3, so if the link training fails at HBR3 we need to know if HOBL was active.The additional boolean is a better
solution than add a function that will call tgl_get_combo_buf_trans() and check if is a HOBL table or duplicate the checks for the conditions to have
HOBL active.

> 
> > +		intel_de_rmw(dev_priv, ICL_PORT_CL_DW10(phy), val,
> > +			     intel_dp->hobl_active ? val : 0);
> > +	}
> > +
> >  	/* 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..5e6634b55e84 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_failed : 1, hobl_active : 1;
> >  };
> >  
> >  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 a23ed7290843..f2c8b56be9ea 100644
> > --- a/drivers/gpu/drm/i915/display/intel_dp_link_training.c
> > +++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
> > @@ -410,10 +410,17 @@ 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_get_link_train_fallback_values(intel_dp,
> > -						     intel_dp->link_rate,
> > -						     intel_dp->lane_count))
> > -		/* Schedule a Hotplug Uevent to userspace to start modeset */
> > -		schedule_work(&intel_connector->modeset_retry_work);
> > -	return;
> > +
> > +	if (intel_dp->hobl_active) {
> > +		drm_dbg_kms(&dp_to_i915(intel_dp)->drm,
> > +			    "Link Training failed with HOBL active, not enabling it from now on");
> > +		intel_dp->hobl_failed = true;
> > +	} else if (intel_dp_get_link_train_fallback_values(intel_dp,
> > +							   intel_dp->link_rate,
> > +							   intel_dp->lane_count)) {
> > +		return;
> > +	}
> > +
> > +	/* Schedule a Hotplug Uevent to userspace to start modeset */
> > +	schedule_work(&intel_connector->modeset_retry_work);
> >  }
> > 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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