drm/i915/eDP: do not write power sequence registers for ghost eDP

Some machines detect an eDP port even if it's not really there, and eDP
initialization has a fail path for this. Typically such machines have an
LVDS display instead. A regression introduced in

commit 82ed61fa
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date:   Sat Oct 20 20:57:41 2012 +0200

    drm/i915: make edp panel power sequence setup more robust

updated the power sequence registers PCH_PP_ON_DELAYS, PCH_PP_OFF_DELAYS,
and PCH_PP_DIVISOR also in the ghost eDP case, messing up the LVDS display.

Split the power sequencer initialization into two, delaying the register
updates until after we know the eDP is real.

Note: Keep the PP_CONTROL unlocking in the first part, even if it does not
update registers, per the commit message of the above mentioned commit.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=52601Reported-and-tested-by: Ryan Coe <ryan@rycomotorsports.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_dp.c

@@ -2579,7 +2579,8 @@ intel_dp_add_properties(struct intel_dp *intel_dp, struct drm_connector *connect
 
 static void
 intel_dp_init_panel_power_sequencer(struct drm_device *dev,
-				    struct intel_dp *intel_dp)
+				    struct intel_dp *intel_dp,
+				    struct edp_power_seq *out)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	struct edp_power_seq cur, vbt, spec, final;
@@ -2650,16 +2651,35 @@ intel_dp_init_panel_power_sequencer(struct drm_device *dev,
 	intel_dp->panel_power_cycle_delay = get_delay(t11_t12);
 #undef get_delay
 
+	DRM_DEBUG_KMS("panel power up delay %d, power down delay %d, power cycle delay %d\n",
+		      intel_dp->panel_power_up_delay, intel_dp->panel_power_down_delay,
+		      intel_dp->panel_power_cycle_delay);
+
+	DRM_DEBUG_KMS("backlight on delay %d, off delay %d\n",
+		      intel_dp->backlight_on_delay, intel_dp->backlight_off_delay);
+
+	if (out)
+		*out = final;
+}
+
+static void
+intel_dp_init_panel_power_sequencer_registers(struct drm_device *dev,
+					      struct intel_dp *intel_dp,
+					      struct edp_power_seq *seq)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	u32 pp_on, pp_off, pp_div;
+
 	/* And finally store the new values in the power sequencer. */
-	pp_on = (final.t1_t3 << PANEL_POWER_UP_DELAY_SHIFT) |
-		(final.t8 << PANEL_LIGHT_ON_DELAY_SHIFT);
-	pp_off = (final.t9 << PANEL_LIGHT_OFF_DELAY_SHIFT) |
-		 (final.t10 << PANEL_POWER_DOWN_DELAY_SHIFT);
+	pp_on = (seq->t1_t3 << PANEL_POWER_UP_DELAY_SHIFT) |
+		(seq->t8 << PANEL_LIGHT_ON_DELAY_SHIFT);
+	pp_off = (seq->t9 << PANEL_LIGHT_OFF_DELAY_SHIFT) |
+		 (seq->t10 << PANEL_POWER_DOWN_DELAY_SHIFT);
 	/* Compute the divisor for the pp clock, simply match the Bspec
 	 * formula. */
 	pp_div = ((100 * intel_pch_rawclk(dev))/2 - 1)
 			<< PP_REFERENCE_DIVIDER_SHIFT;
-	pp_div |= (DIV_ROUND_UP(final.t11_t12, 1000)
+	pp_div |= (DIV_ROUND_UP(seq->t11_t12, 1000)
 			<< PANEL_POWER_CYCLE_DELAY_SHIFT);
 
 	/* Haswell doesn't have any port selection bits for the panel
@@ -2675,14 +2695,6 @@ intel_dp_init_panel_power_sequencer(struct drm_device *dev,
 	I915_WRITE(PCH_PP_OFF_DELAYS, pp_off);
 	I915_WRITE(PCH_PP_DIVISOR, pp_div);
 
-
-	DRM_DEBUG_KMS("panel power up delay %d, power down delay %d, power cycle delay %d\n",
-		      intel_dp->panel_power_up_delay, intel_dp->panel_power_down_delay,
-		      intel_dp->panel_power_cycle_delay);
-
-	DRM_DEBUG_KMS("backlight on delay %d, off delay %d\n",
-		      intel_dp->backlight_on_delay, intel_dp->backlight_off_delay);
-
 	DRM_DEBUG_KMS("panel power sequencer register settings: PP_ON %#x, PP_OFF %#x, PP_DIV %#x\n",
 		      I915_READ(PCH_PP_ON_DELAYS),
 		      I915_READ(PCH_PP_OFF_DELAYS),
@@ -2699,6 +2711,7 @@ intel_dp_init_connector(struct intel_digital_port *intel_dig_port,
 	struct drm_device *dev = intel_encoder->base.dev;
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	struct drm_display_mode *fixed_mode = NULL;
+	struct edp_power_seq power_seq = { 0 };
 	enum port port = intel_dig_port->port;
 	const char *name = NULL;
 	int type;
@@ -2771,7 +2784,7 @@ intel_dp_init_connector(struct intel_digital_port *intel_dig_port,
 	}
 
 	if (is_edp(intel_dp))
-		intel_dp_init_panel_power_sequencer(dev, intel_dp);
+		intel_dp_init_panel_power_sequencer(dev, intel_dp, &power_seq);
 
 	intel_dp_i2c_init(intel_dp, intel_connector, name);
 
@@ -2798,6 +2811,10 @@ intel_dp_init_connector(struct intel_digital_port *intel_dig_port,
 			return;
 		}
 
+		/* We now know it's not a ghost, init power sequence regs. */
+		intel_dp_init_panel_power_sequencer_registers(dev, intel_dp,
+							      &power_seq);
+
 		ironlake_edp_panel_vdd_on(intel_dp);
 		edid = drm_get_edid(connector, &intel_dp->adapter);
 		if (edid) {