commit 357c0ae9198ad7f526f229c4f33921e8e3a3e9a0
author Imre Deak <imre.deak@intel.com> Mon Nov 21 21:15:06 2016 +0200
committer Imre Deak <imre.deak@intel.com> Wed Nov 23 13:32:01 2016 +0200
tree 9266b64f1f7182c060f0569ad8d136f09359a03b
parent dd75f6dd2e7d5de544e8aa8b75d1e50308cd8561

drm/i915/lspcon: Wait for expected LSPCON mode to settle

Some LSPCON adaptors may return an incorrect LSPCON mode right after
waking from DP Sleep state. This is the case at least for the ParadTech
PS175 adaptor, both when waking because of exiting the DP Sleep to
active state, or due to any other AUX CH transfer. We can determine the
current expected mode based on whether the DPCD area is accessible,
since according to the LSPCON spec this area is only accesible
in PCON mode.

This wait will avoid us trying to change the mode, while the current
expected mode hasn't settled yet and start link training before the
adaptor thinks it's in PCON mode after waking from DP Sleep state.

Cc: Shashank Sharma <shashank.sharma@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Shashank Sharma <shashank.sharma@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1479755707-29596-4-git-send-email-imre.deak@intel.com

drivers/gpu/drm/i915/intel_lspcon.c

diff --git a/drivers/gpu/drm/i915/intel_lspcon.c b/drivers/gpu/drm/i915/intel_lspcon.c
index 5013124..281127d 100644
--- a/drivers/gpu/drm/i915/intel_lspcon.c
+++ b/drivers/gpu/drm/i915/intel_lspcon.c
@@ -35,16 +35,54 @@
 	return &dig_port->dp;
 }
 
+static const char *lspcon_mode_name(enum drm_lspcon_mode mode)
+{
+	switch (mode) {
+	case DRM_LSPCON_MODE_PCON:
+		return "PCON";
+	case DRM_LSPCON_MODE_LS:
+		return "LS";
+	case DRM_LSPCON_MODE_INVALID:
+		return "INVALID";
+	default:
+		MISSING_CASE(mode);
+		return "INVALID";
+	}
+}
+
 static enum drm_lspcon_mode lspcon_get_current_mode(struct intel_lspcon *lspcon)
 {
-	enum drm_lspcon_mode current_mode = DRM_LSPCON_MODE_INVALID;
+	enum drm_lspcon_mode current_mode;
 	struct i2c_adapter *adapter = &lspcon_to_intel_dp(lspcon)->aux.ddc;
 
-	if (drm_lspcon_get_mode(adapter, &current_mode))
+	if (drm_lspcon_get_mode(adapter, &current_mode)) {
 		DRM_ERROR("Error reading LSPCON mode\n");
-	else
-		DRM_DEBUG_KMS("Current LSPCON mode %s\n",
-			current_mode == DRM_LSPCON_MODE_PCON ? "PCON" : "LS");
+		return DRM_LSPCON_MODE_INVALID;
+	}
+	return current_mode;
+}
+
+static enum drm_lspcon_mode lspcon_wait_mode(struct intel_lspcon *lspcon,
+					     enum drm_lspcon_mode mode)
+{
+	enum drm_lspcon_mode current_mode;
+
+	current_mode = lspcon_get_current_mode(lspcon);
+	if (current_mode == mode || current_mode == DRM_LSPCON_MODE_INVALID)
+		goto out;
+
+	DRM_DEBUG_KMS("Waiting for LSPCON mode %s to settle\n",
+		      lspcon_mode_name(mode));
+
+	wait_for((current_mode = lspcon_get_current_mode(lspcon)) == mode ||
+		 current_mode == DRM_LSPCON_MODE_INVALID, 100);
+	if (current_mode != mode)
+		DRM_DEBUG_KMS("LSPCON mode hasn't settled\n");
+
+out:
+	DRM_DEBUG_KMS("Current LSPCON mode %s\n",
+		      lspcon_mode_name(current_mode));
+
 	return current_mode;
 }
 
@@ -97,8 +135,10 @@
 {
 	enum drm_dp_dual_mode_type adaptor_type;
 	struct i2c_adapter *adapter = &lspcon_to_intel_dp(lspcon)->aux.ddc;
+	enum drm_lspcon_mode expected_mode;
 
-	lspcon_wake_native_aux_ch(lspcon);
+	expected_mode = lspcon_wake_native_aux_ch(lspcon) ?
+			DRM_LSPCON_MODE_PCON : DRM_LSPCON_MODE_LS;
 
 	/* Lets probe the adaptor and check its type */
 	adaptor_type = drm_dp_dual_mode_detect(adapter);
@@ -110,7 +150,7 @@
 
 	/* Yay ... got a LSPCON device */
 	DRM_DEBUG_KMS("LSPCON detected\n");
-	lspcon->mode = lspcon_get_current_mode(lspcon);
+	lspcon->mode = lspcon_wait_mode(lspcon, expected_mode);
 	lspcon->active = true;
 	return true;
 }
@@ -150,8 +190,17 @@
 
 void lspcon_resume(struct intel_lspcon *lspcon)
 {
-	if (lspcon_wake_native_aux_ch(lspcon))
+	enum drm_lspcon_mode expected_mode;
+
+	if (lspcon_wake_native_aux_ch(lspcon)) {
+		expected_mode = DRM_LSPCON_MODE_PCON;
 		lspcon_resume_in_pcon_wa(lspcon);
+	} else {
+		expected_mode = DRM_LSPCON_MODE_LS;
+	}
+
+	if (lspcon_wait_mode(lspcon, expected_mode) == DRM_LSPCON_MODE_PCON)
+		return;
 
 	if (lspcon_change_mode(lspcon, DRM_LSPCON_MODE_PCON, true))
 		DRM_ERROR("LSPCON resume failed\n");
@@ -159,6 +208,11 @@
 		DRM_DEBUG_KMS("LSPCON resume success\n");
 }
 
+void lspcon_wait_pcon_mode(struct intel_lspcon *lspcon)
+{
+	lspcon_wait_mode(lspcon, DRM_LSPCON_MODE_PCON);
+}
+
 bool lspcon_init(struct intel_digital_port *intel_dig_port)
 {
 	struct intel_dp *dp = &intel_dig_port->dp;