drm/i915: Fix up cpt pixel multiplier enable sequence

Bspec for the "DPLL HDMI multiplier" field says:

"Restriction : The DPLL must be enabled and stable before setting these bits.
These bits must be programmed after DPLL_SEL is programmed."

There is apparently no restriction on programming the DPLL_SEL
register wrt the DPLL. So let's just move that up before we enable the
pch dpll.
Reviewed-by: Imre Deak <imre.deak@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_display.c

@@ -3004,15 +3004,8 @@ static void ironlake_pch_enable(struct drm_crtc *crtc)
 	/* For PCH output, training FDI link */
 	dev_priv->display.fdi_link_train(crtc);
 
-	/* XXX: pch pll's can be enabled any time before we enable the PCH
-	 * transcoder, and we actually should do this to not upset any PCH
-	 * transcoder that already use the clock when we share it.
-	 *
-	 * Note that enable_shared_dpll tries to do the right thing, but
-	 * get_shared_dpll unconditionally resets the pll - we need that to have
-	 * the right LVDS enable sequence. */
-	ironlake_enable_shared_dpll(intel_crtc);
-
+	/* We need to program the right clock selection before writing the pixel
+	 * mutliplier into the DPLL. */
 	if (HAS_PCH_CPT(dev)) {
 		u32 sel;
 
@@ -3026,6 +3019,15 @@ static void ironlake_pch_enable(struct drm_crtc *crtc)
 		I915_WRITE(PCH_DPLL_SEL, temp);
 	}
 
+	/* XXX: pch pll's can be enabled any time before we enable the PCH
+	 * transcoder, and we actually should do this to not upset any PCH
+	 * transcoder that already use the clock when we share it.
+	 *
+	 * Note that enable_shared_dpll tries to do the right thing, but
+	 * get_shared_dpll unconditionally resets the pll - we need that to have
+	 * the right LVDS enable sequence. */
+	ironlake_enable_shared_dpll(intel_crtc);
+
 	/* set transcoder timing, panel must allow it */
 	assert_panel_unlocked(dev_priv, pipe);
 	ironlake_pch_transcoder_set_timings(intel_crtc, pipe);