drm/i915: Force common lane on for the PPS kick on CHV

With DPIO powergating active the DPLL can't be accessed unless
something else is keeping the common lane in the channel on.
That means the PPS kick procedure could fail to enable the PLL.

Power up some data lanes to force the common lane to power up
so that the PLL can be enabled temporarily.

v2: Avoid gcc uninitilized variable warning
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Deepak S <deepak.s@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_dp.c

@@ -341,7 +341,9 @@ vlv_power_sequencer_kick(struct intel_dp *intel_dp)
 	struct drm_device *dev = intel_dig_port->base.base.dev;
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	enum pipe pipe = intel_dp->pps_pipe;
-	bool pll_enabled;
+	bool pll_enabled, release_cl_override = false;
+	enum dpio_phy phy = DPIO_PHY(pipe);
+	enum dpio_channel ch = vlv_pipe_to_channel(pipe);
 	uint32_t DP;
 
 	if (WARN(I915_READ(intel_dp->output_reg) & DP_PORT_EN,
@@ -371,9 +373,13 @@ vlv_power_sequencer_kick(struct intel_dp *intel_dp)
 	 * The DPLL for the pipe must be enabled for this to work.
 	 * So enable temporarily it if it's not already enabled.
 	 */
-	if (!pll_enabled)
+	if (!pll_enabled) {
+		release_cl_override = IS_CHERRYVIEW(dev) &&
+			!chv_phy_powergate_ch(dev_priv, phy, ch, true);
+
 		vlv_force_pll_on(dev, pipe, IS_CHERRYVIEW(dev) ?
 				 &chv_dpll[0].dpll : &vlv_dpll[0].dpll);
+	}
 
 	/*
 	 * Similar magic as in intel_dp_enable_port().
@@ -390,8 +396,12 @@ vlv_power_sequencer_kick(struct intel_dp *intel_dp)
 	I915_WRITE(intel_dp->output_reg, DP & ~DP_PORT_EN);
 	POSTING_READ(intel_dp->output_reg);
 
-	if (!pll_enabled)
+	if (!pll_enabled) {
 		vlv_force_pll_off(dev, pipe);
+
+		if (release_cl_override)
+			chv_phy_powergate_ch(dev_priv, phy, ch, false);
+	}
 }
 
 static enum pipe