drm/i915: Simplify ironlake_crtc_compute_clock() CPU eDP case

None of the code in ironlake_crtc_compute_clock() is relevant for CPU
eDP. The CPU eDP PLL is turned on and off in ironlake_edp_pll_{on,off}
from the DP code and that doesn't depend on the crtc_state->dpll values,
so just return early in that case.

v2: Rebase without patch that drops lvds downclock code. (Ville)
Signed-off-by: Ander Conselvan de Oliveira <ander.conselvan.de.oliveira@intel.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1458576016-30348-9-git-send-email-ander.conselvan.de.oliveira@intel.com

drivers/gpu/drm/i915/intel_display.c

@@ -8800,13 +8800,16 @@ static int ironlake_crtc_compute_clock(struct intel_crtc *crtc,
 	intel_clock_t clock, reduced_clock;
 	u32 dpll = 0, fp = 0, fp2 = 0;
 	bool has_reduced_clock = false;
-	bool is_lvds = false;
 	struct intel_shared_dpll *pll;
 
 	memset(&crtc_state->dpll_hw_state, 0,
 	       sizeof(crtc_state->dpll_hw_state));
 
-	is_lvds = intel_pipe_will_have_type(crtc_state, INTEL_OUTPUT_LVDS);
+	crtc->lowfreq_avail = false;
+
+	/* CPU eDP is the only output that doesn't need a PCH PLL of its own. */
+	if (!crtc_state->has_pch_encoder)
+		return 0;
 
 	if (!crtc_state->clock_set) {
 		if (!ironlake_compute_clocks(&crtc->base, crtc_state, &clock,
@@ -8824,8 +8827,6 @@ static int ironlake_crtc_compute_clock(struct intel_crtc *crtc,
 		crtc_state->dpll.p2 = clock.p2;
 	}
 
-	/* CPU eDP is the only output that doesn't need a PCH PLL of its own. */
-	if (crtc_state->has_pch_encoder) {
 	fp = i9xx_dpll_compute_fp(&crtc_state->dpll);
 	if (has_reduced_clock)
 		fp2 = i9xx_dpll_compute_fp(&reduced_clock);
@@ -8846,12 +8847,10 @@ static int ironlake_crtc_compute_clock(struct intel_crtc *crtc,
 				 pipe_name(crtc->pipe));
 		return -EINVAL;
 	}
-	}
 
-	if (is_lvds && has_reduced_clock)
+	if (intel_pipe_will_have_type(crtc_state, INTEL_OUTPUT_LVDS) &&
+	    has_reduced_clock)
 		crtc->lowfreq_avail = true;
-	else
-		crtc->lowfreq_avail = false;
 
 	return 0;
 }