drm/i915/dp: abstract training pattern selection

Make it cleaner to add more checks in the function. No functional
changes.

Cc: Ander Conselvan de Oliveira <conselvan2@gmail.com>
Cc: Sivakumar Thulasimani <sivakumar.thulasimani@intel.com>
Reviewed-by: Sivakumar Thulasimani <sivakumar.thulasimani@intel.com>
Cc: drm-intel-fixes@lists.freedesktop.org # dependency on the next patch
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1454667370-8001-1-git-send-email-jani.nikula@intel.com
(cherry picked from commit 23a5110d)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

drivers/gpu/drm/i915/intel_dp_link_training.c

@@ -215,16 +215,15 @@ intel_dp_link_training_clock_recovery(struct intel_dp *intel_dp)
 	}
 }
 
-static void
-intel_dp_link_training_channel_equalization(struct intel_dp *intel_dp)
+/*
+ * Pick training pattern for channel equalization. Training Pattern 3 for HBR2
+ * or 1.2 devices that support it, Training Pattern 2 otherwise.
+ */
+static u32 intel_dp_training_pattern(struct intel_dp *intel_dp)
 {
-	bool channel_eq = false;
-	int tries, cr_tries;
-	uint32_t training_pattern = DP_TRAINING_PATTERN_2;
+	u32 training_pattern = DP_TRAINING_PATTERN_2;
 
 	/*
-	 * Training Pattern 3 for HBR2 or 1.2 devices that support it.
-	 *
 	 * Intel platforms that support HBR2 also support TPS3. TPS3 support is
 	 * also mandatory for downstream devices that support HBR2.
 	 *
@@ -237,6 +236,18 @@ intel_dp_link_training_channel_equalization(struct intel_dp *intel_dp)
 	else if (intel_dp->link_rate == 540000)
 		DRM_ERROR("5.4 Gbps link rate without HBR2/TPS3 support\n");
 
+	return training_pattern;
+}
+
+static void
+intel_dp_link_training_channel_equalization(struct intel_dp *intel_dp)
+{
+	bool channel_eq = false;
+	int tries, cr_tries;
+	u32 training_pattern;
+
+	training_pattern = intel_dp_training_pattern(intel_dp);
+
 	/* channel equalization */
 	if (!intel_dp_set_link_train(intel_dp,
 				     training_pattern |