drm/i915/edp: fix eDP MSO pipe sanity checks for ADL-P

ADL-P supports stream splitter on pipe B in addition to pipe A. Update
the sanity check in intel_ddi_mso_get_config() to reflect this, and
remove the check in intel_ddi_mso_configure() as redundant with
encoder->pipe_mask. Abstract the splitter pipe mask to a single point of
truth while at it to avoid similar mistakes in the future.

Fixes: 7bc188cc ("drm/i915/adl_p: enable MSO on pipe B")
Cc: Uma Shankar <uma.shankar@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Swati Sharma <swati2.sharma@intel.com>
Reviewed-by: Swati Sharma <swati2.sharma@intel.com>
Tested-by: Swati Sharma <swati2.sharma@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210812132354.10885-1-jani.nikula@intel.com
(cherry picked from commit f6864b27)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

drivers/gpu/drm/i915/display/intel_ddi.c

@@ -2463,6 +2463,15 @@ static void intel_ddi_power_up_lanes(struct intel_encoder *encoder,
 	}
 }
 
+/* Splitter enable for eDP MSO is limited to certain pipes. */
+static u8 intel_ddi_splitter_pipe_mask(struct drm_i915_private *i915)
+{
+	if (IS_ALDERLAKE_P(i915))
+		return BIT(PIPE_A) | BIT(PIPE_B);
+	else
+		return BIT(PIPE_A);
+}
+
 static void intel_ddi_mso_get_config(struct intel_encoder *encoder,
 				     struct intel_crtc_state *pipe_config)
 {
@@ -2480,8 +2489,7 @@ static void intel_ddi_mso_get_config(struct intel_encoder *encoder,
 	if (!pipe_config->splitter.enable)
 		return;
 
-	/* Splitter enable is supported for pipe A only. */
-	if (drm_WARN_ON(&i915->drm, pipe != PIPE_A)) {
+	if (drm_WARN_ON(&i915->drm, !(intel_ddi_splitter_pipe_mask(i915) & BIT(pipe)))) {
 		pipe_config->splitter.enable = false;
 		return;
 	}
@@ -2513,10 +2521,6 @@ static void intel_ddi_mso_configure(const struct intel_crtc_state *crtc_state)
 		return;
 
 	if (crtc_state->splitter.enable) {
-		/* Splitter enable is supported for pipe A only. */
-		if (drm_WARN_ON(&i915->drm, pipe != PIPE_A))
-			return;
-
 		dss1 |= SPLITTER_ENABLE;
 		dss1 |= OVERLAP_PIXELS(crtc_state->splitter.pixel_overlap);
 		if (crtc_state->splitter.link_count == 2)
@@ -4743,12 +4747,8 @@ void intel_ddi_init(struct drm_i915_private *dev_priv, enum port port)
 
 		dig_port->hpd_pulse = intel_dp_hpd_pulse;
 
-		/* Splitter enable for eDP MSO is limited to certain pipes. */
-		if (dig_port->dp.mso_link_count) {
-			encoder->pipe_mask = BIT(PIPE_A);
-			if (IS_ALDERLAKE_P(dev_priv))
-				encoder->pipe_mask |= BIT(PIPE_B);
-		}
+		if (dig_port->dp.mso_link_count)
+			encoder->pipe_mask = intel_ddi_splitter_pipe_mask(dev_priv);
 	}
 
 	/* In theory we don't need the encoder->type check, but leave it just in