drm/i915: Add lspcon resume function

As per the software design, we are driving lspcon in
PCON mode. But while resuming from suspend, lspcon can go
in LS mode (which is its default operating mode on power on)

This patch adds a resume function for lspcon, which makes sure
its operating in PCON mode, post resume.

V2: Address review comments from Imre
	- move lspcon_resume call to encoder->reset()
	- use early returns

Signed-off-by: Shashank Sharma <shashank.sharma@intel.com>
Reviewed-by: Imre Deak <imre.deak@intel.com>
Acked-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1476455212-27893-6-git-send-email-shashank.sharma@intel.com

drivers/gpu/drm/i915/intel_dp.c

@@ -4780,11 +4780,16 @@ static void intel_edp_panel_vdd_sanitize(struct intel_dp *intel_dp)
 void intel_dp_encoder_reset(struct drm_encoder *encoder)
 {
 	struct drm_i915_private *dev_priv = to_i915(encoder->dev);
-	struct intel_dp *intel_dp = enc_to_intel_dp(encoder);
+	struct intel_digital_port *intel_dig_port = enc_to_dig_port(encoder);
+	struct intel_lspcon *lspcon = &intel_dig_port->lspcon;
+	struct intel_dp *intel_dp = &intel_dig_port->dp;
 
 	if (!HAS_DDI(dev_priv))
 		intel_dp->DP = I915_READ(intel_dp->output_reg);
 
+	if (IS_GEN9(dev_priv) && lspcon->active)
+		lspcon_resume(lspcon);
+
 	if (to_intel_encoder(encoder)->type != INTEL_OUTPUT_EDP)
 		return;
 

drivers/gpu/drm/i915/intel_drv.h

@@ -1857,4 +1857,5 @@ void intel_color_load_luts(struct drm_crtc_state *crtc_state);
 
 /* intel_lspcon.c */
 bool lspcon_init(struct intel_digital_port *intel_dig_port);
+void lspcon_resume(struct intel_lspcon *lspcon);
 #endif /* __INTEL_DRV_H__ */

drivers/gpu/drm/i915/intel_lspcon.c

@@ -89,6 +89,14 @@ static bool lspcon_probe(struct intel_lspcon *lspcon)
 	return true;
 }
 
+void lspcon_resume(struct intel_lspcon *lspcon)
+{
+	if (lspcon_change_mode(lspcon, DRM_LSPCON_MODE_PCON, true))
+		DRM_ERROR("LSPCON resume failed\n");
+	else
+		DRM_DEBUG_KMS("LSPCON resume success\n");
+}
+
 bool lspcon_init(struct intel_digital_port *intel_dig_port)
 {
 	struct intel_dp *dp = &intel_dig_port->dp;