drm/i915: Adjust system agent voltage on CNL if required by DDI ports

On CNL we may need to bump up the system agent voltage not only due
to CDCLK but also when driving DDI port with a sufficiently high clock.
To that end start tracking the minimum acceptable voltage for each crtc.
We do the tracking via crtcs because we don't have any kind of encoder
state. Also there's no downside to doing it this way, and it matches how
we track cdclk requirements on account of pixel rate.

v2: Allow disabled crtcs to use the min voltage
    Add IS_CNL check to intel_ddi_compute_min_voltage() since
    we're using CNL specific values there
    s/intel_compute_min_voltage/cnl_compute_min_voltage/ since
    the function makes hw specific assumptions about the voltage
    values
v3: Drop the test hack leftovers from skl_modeset_calc_cdclk()
v4: s/voltage/voltage_level/ (Rodrigo)
    Replace DPLL DVFS FIXMEs with an explanation why we don't
    do anything there (Rodrigo)

Cc: Mika Kahola <mika.kahola@intel.com>
Cc: Manasi Navare <manasi.d.navare@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171024095216.1638-9-ville.syrjala@linux.intel.com

drivers/gpu/drm/i915/i915_drv.h

@@ -2416,6 +2416,8 @@ struct drm_i915_private {
 	unsigned int active_crtcs;
 	/* minimum acceptable cdclk for each pipe */
 	int min_cdclk[I915_MAX_PIPES];
+	/* minimum acceptable voltage level for each pipe */
+	u8 min_voltage_level[I915_MAX_PIPES];
 
 	int dpio_phy_iosf_port[I915_NUM_PHYS_VLV];
 

drivers/gpu/drm/i915/intel_cdclk.c

@@ -1665,6 +1665,12 @@ static void cnl_set_cdclk(struct drm_i915_private *dev_priv,
 	mutex_unlock(&dev_priv->pcu_lock);
 
 	intel_update_cdclk(dev_priv);
+
+	/*
+	 * Can't read out the voltage level :(
+	 * Let's just assume everything is as expected.
+	 */
+	dev_priv->cdclk.hw.voltage_level = cdclk_state->voltage_level;
 }
 
 static int cnl_cdclk_pll_vco(struct drm_i915_private *dev_priv, int cdclk)
@@ -1934,6 +1940,43 @@ static int intel_compute_min_cdclk(struct drm_atomic_state *state)
 	return min_cdclk;
 }
 
+/*
+ * Note that this functions assumes that 0 is
+ * the lowest voltage value, and higher values
+ * correspond to increasingly higher voltages.
+ *
+ * Should that relationship no longer hold on
+ * future platforms this code will need to be
+ * adjusted.
+ */
+static u8 cnl_compute_min_voltage_level(struct intel_atomic_state *state)
+{
+	struct drm_i915_private *dev_priv = to_i915(state->base.dev);
+	struct intel_crtc *crtc;
+	struct intel_crtc_state *crtc_state;
+	u8 min_voltage_level;
+	int i;
+	enum pipe pipe;
+
+	memcpy(state->min_voltage_level, dev_priv->min_voltage_level,
+	       sizeof(state->min_voltage_level));
+
+	for_each_new_intel_crtc_in_state(state, crtc, crtc_state, i) {
+		if (crtc_state->base.enable)
+			state->min_voltage_level[i] =
+				crtc_state->min_voltage_level;
+		else
+			state->min_voltage_level[i] = 0;
+	}
+
+	min_voltage_level = 0;
+	for_each_pipe(dev_priv, pipe)
+		min_voltage_level = max(state->min_voltage_level[pipe],
+					min_voltage_level);
+
+	return min_voltage_level;
+}
+
 static int vlv_modeset_calc_cdclk(struct drm_atomic_state *state)
 {
 	struct drm_i915_private *dev_priv = to_i915(state->dev);
@@ -2097,7 +2140,8 @@ static int cnl_modeset_calc_cdclk(struct drm_atomic_state *state)
 	intel_state->cdclk.logical.vco = vco;
 	intel_state->cdclk.logical.cdclk = cdclk;
 	intel_state->cdclk.logical.voltage_level =
-		cnl_calc_voltage_level(cdclk);
+		max(cnl_calc_voltage_level(cdclk),
+		    cnl_compute_min_voltage_level(intel_state));
 
 	if (!intel_state->active_crtcs) {
 		cdclk = cnl_calc_cdclk(0);

drivers/gpu/drm/i915/intel_ddi.c

@@ -2542,6 +2542,13 @@ bool intel_ddi_is_audio_enabled(struct drm_i915_private *dev_priv,
 	return false;
 }
 
+void intel_ddi_compute_min_voltage_level(struct drm_i915_private *dev_priv,
+					 struct intel_crtc_state *crtc_state)
+{
+	if (IS_CANNONLAKE(dev_priv) && crtc_state->port_clock > 594000)
+		crtc_state->min_voltage_level = 2;
+}
+
 void intel_ddi_get_config(struct intel_encoder *encoder,
 			  struct intel_crtc_state *pipe_config)
 {
@@ -2641,6 +2648,8 @@ void intel_ddi_get_config(struct intel_encoder *encoder,
 	if (IS_GEN9_LP(dev_priv))
 		pipe_config->lane_lat_optim_mask =
 			bxt_ddi_phy_get_lane_lat_optim_mask(encoder);
+
+	intel_ddi_compute_min_voltage_level(dev_priv, pipe_config);
 }
 
 static bool intel_ddi_compute_config(struct intel_encoder *encoder,
@@ -2667,6 +2676,8 @@ static bool intel_ddi_compute_config(struct intel_encoder *encoder,
 			bxt_ddi_phy_calc_lane_lat_optim_mask(encoder,
 							     pipe_config->lane_count);
 
+	intel_ddi_compute_min_voltage_level(dev_priv, pipe_config);
+
 	return ret;
 
 }

drivers/gpu/drm/i915/intel_display.c

@@ -5938,6 +5938,7 @@ static void intel_crtc_disable_noatomic(struct drm_crtc *crtc,
 
 	dev_priv->active_crtcs &= ~(1 << intel_crtc->pipe);
 	dev_priv->min_cdclk[intel_crtc->pipe] = 0;
+	dev_priv->min_voltage_level[intel_crtc->pipe] = 0;
 }
 
 /*
@@ -11289,6 +11290,8 @@ intel_pipe_config_compare(struct drm_i915_private *dev_priv,
 	PIPE_CONF_CHECK_CLOCK_FUZZY(base.adjusted_mode.crtc_clock);
 	PIPE_CONF_CHECK_CLOCK_FUZZY(port_clock);
 
+	PIPE_CONF_CHECK_I(min_voltage_level);
+
 #undef PIPE_CONF_CHECK_X
 #undef PIPE_CONF_CHECK_I
 #undef PIPE_CONF_CHECK_P
@@ -11949,6 +11952,9 @@ static int intel_modeset_checks(struct drm_atomic_state *state)
 		DRM_DEBUG_KMS("New cdclk calculated to be logical %u kHz, actual %u kHz\n",
 			      intel_state->cdclk.logical.cdclk,
 			      intel_state->cdclk.actual.cdclk);
+		DRM_DEBUG_KMS("New voltage level calculated to be logical %u, actual %u\n",
+			      intel_state->cdclk.logical.voltage_level,
+			      intel_state->cdclk.actual.voltage_level);
 	} else {
 		to_intel_atomic_state(state)->cdclk.logical = dev_priv->cdclk.logical;
 	}
@@ -12517,6 +12523,9 @@ static int intel_atomic_commit(struct drm_device *dev,
 	if (intel_state->modeset) {
 		memcpy(dev_priv->min_cdclk, intel_state->min_cdclk,
 		       sizeof(intel_state->min_cdclk));
+		memcpy(dev_priv->min_voltage_level,
+		       intel_state->min_voltage_level,
+		       sizeof(intel_state->min_voltage_level));
 		dev_priv->active_crtcs = intel_state->active_crtcs;
 		dev_priv->cdclk.logical = intel_state->cdclk.logical;
 		dev_priv->cdclk.actual = intel_state->cdclk.actual;
@@ -15027,6 +15036,8 @@ static void intel_modeset_readout_hw_state(struct drm_device *dev)
 		}
 
 		dev_priv->min_cdclk[crtc->pipe] = min_cdclk;
+		dev_priv->min_voltage_level[crtc->pipe] =
+			crtc_state->min_voltage_level;
 
 		intel_pipe_config_sanity_check(dev_priv, crtc_state);
 	}

drivers/gpu/drm/i915/intel_dp_mst.c

@@ -34,6 +34,7 @@ static bool intel_dp_mst_compute_config(struct intel_encoder *encoder,
 					struct intel_crtc_state *pipe_config,
 					struct drm_connector_state *conn_state)
 {
+	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
 	struct intel_dp_mst_encoder *intel_mst = enc_to_mst(&encoder->base);
 	struct intel_digital_port *intel_dig_port = intel_mst->primary;
 	struct intel_dp *intel_dp = &intel_dig_port->dp;
@@ -87,6 +88,8 @@ static bool intel_dp_mst_compute_config(struct intel_encoder *encoder,
 
 	pipe_config->dp_m_n.tu = slots;
 
+	intel_ddi_compute_min_voltage_level(dev_priv, pipe_config);
+
 	return true;
 }
 
@@ -307,6 +310,8 @@ static void intel_dp_mst_enc_get_config(struct intel_encoder *encoder,
 	intel_dp_get_m_n(crtc, pipe_config);
 
 	intel_ddi_clock_get(&intel_dig_port->base, pipe_config);
+
+	intel_ddi_compute_min_voltage_level(dev_priv, pipe_config);
 }
 
 static int intel_dp_mst_get_ddc_modes(struct drm_connector *connector)

drivers/gpu/drm/i915/intel_dpll_mgr.c

@@ -2008,8 +2008,8 @@ static void cnl_ddi_pll_enable(struct drm_i915_private *dev_priv,
 	 * requirement, follow the Display Voltage Frequency Switching
 	 * Sequence Before Frequency Change
 	 *
-	 * FIXME: (DVFS) is used to adjust the display voltage to match the
-	 * display clock frequencies
+	 * Note: DVFS is actually handled via the cdclk code paths,
+	 * hence we do nothing here.
 	 */
 
 	/* 6. Enable DPLL in DPLL_ENABLE. */
@@ -2030,8 +2030,8 @@ static void cnl_ddi_pll_enable(struct drm_i915_private *dev_priv,
 	 * requirement, follow the Display Voltage Frequency Switching
 	 * Sequence After Frequency Change
 	 *
-	 * FIXME: (DVFS) is used to adjust the display voltage to match the
-	 * display clock frequencies
+	 * Note: DVFS is actually handled via the cdclk code paths,
+	 * hence we do nothing here.
 	 */
 
 	/*
@@ -2055,8 +2055,8 @@ static void cnl_ddi_pll_disable(struct drm_i915_private *dev_priv,
 	 * requirement, follow the Display Voltage Frequency Switching
 	 * Sequence Before Frequency Change
 	 *
-	 * FIXME: (DVFS) is used to adjust the display voltage to match the
-	 * display clock frequencies
+	 * Note: DVFS is actually handled via the cdclk code paths,
+	 * hence we do nothing here.
 	 */
 
 	/* 3. Disable DPLL through DPLL_ENABLE. */
@@ -2077,8 +2077,8 @@ static void cnl_ddi_pll_disable(struct drm_i915_private *dev_priv,
 	 * requirement, follow the Display Voltage Frequency Switching
 	 * Sequence After Frequency Change
 	 *
-	 * FIXME: (DVFS) is used to adjust the display voltage to match the
-	 * display clock frequencies
+	 * Note: DVFS is actually handled via the cdclk code paths,
+	 * hence we do nothing here.
 	 */
 
 	/* 6. Disable DPLL power in DPLL_ENABLE. */

drivers/gpu/drm/i915/intel_drv.h

@@ -386,6 +386,8 @@ struct intel_atomic_state {
 	unsigned int active_crtcs;
 	/* minimum acceptable cdclk for each pipe */
 	int min_cdclk[I915_MAX_PIPES];
+	/* minimum acceptable voltage level for each pipe */
+	u8 min_voltage_level[I915_MAX_PIPES];
 
 	struct intel_shared_dpll_state shared_dpll[I915_NUM_PLLS];
 
@@ -739,6 +741,9 @@ struct intel_crtc_state {
 	 */
 	uint8_t lane_lat_optim_mask;
 
+	/* minimum acceptable voltage level */
+	u8 min_voltage_level;
+
 	/* Panel fitter controls for gen2-gen4 + VLV */
 	struct {
 		u32 control;
@@ -1293,6 +1298,8 @@ void intel_ddi_clock_get(struct intel_encoder *encoder,
 			 struct intel_crtc_state *pipe_config);
 void intel_ddi_set_vc_payload_alloc(const struct intel_crtc_state *crtc_state,
 				    bool state);
+void intel_ddi_compute_min_voltage_level(struct drm_i915_private *dev_priv,
+					 struct intel_crtc_state *crtc_state);
 u32 bxt_signal_levels(struct intel_dp *intel_dp);
 uint32_t ddi_signal_levels(struct intel_dp *intel_dp);
 u8 intel_ddi_dp_voltage_max(struct intel_encoder *encoder);