drm/i915/dp: make eDP PLL functions work as advertised

Signed-off-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>

drivers/gpu/drm/i915/intel_dp.c

@@ -891,8 +891,10 @@ static void ironlake_edp_pll_on(struct drm_encoder *encoder)
 
 	DRM_DEBUG_KMS("\n");
 	dpa_ctl = I915_READ(DP_A);
-	dpa_ctl &= ~DP_PLL_ENABLE;
+	dpa_ctl |= DP_PLL_ENABLE;
 	I915_WRITE(DP_A, dpa_ctl);
+	POSTING_READ(DP_A);
+	udelay(200);
 }
 
 static void ironlake_edp_pll_off(struct drm_encoder *encoder)
@@ -902,7 +904,7 @@ static void ironlake_edp_pll_off(struct drm_encoder *encoder)
 	u32 dpa_ctl;
 
 	dpa_ctl = I915_READ(DP_A);
-	dpa_ctl |= DP_PLL_ENABLE;
+	dpa_ctl &= ~DP_PLL_ENABLE;
 	I915_WRITE(DP_A, dpa_ctl);
 	POSTING_READ(DP_A);
 	udelay(200);