drm/i915/vlv: reset DPIO on load and resume v2

DPIO needs to have common reset de-asserted on soft resets like boot and
S3.  In some cases, the BIOS will have done this for us, but it should
be safe to do at runtime as well, as long as we do it when the pipes are
otherwise off.

v2: update bit name to match docs better (Ville)
    reset after CRI clock select (Ville)

References: https://bugs.freedesktop.org/show_bug.cgi?id=69166
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_reg.h

@@ -430,7 +430,7 @@
 #define  DPIO_MODSEL1			(1<<3) /* if ref clk b == 27 */
 #define  DPIO_MODSEL0			(1<<2) /* if ref clk a == 27 */
 #define  DPIO_SFR_BYPASS		(1<<1)
-#define  DPIO_RESET			(1<<0)
+#define  DPIO_CMNRST			(1<<0)
 
 #define _DPIO_TX3_SWING_CTL4_A		0x690
 #define _DPIO_TX3_SWING_CTL4_B		0x2a90

drivers/gpu/drm/i915/intel_display.c

@@ -1360,6 +1360,26 @@ static void assert_pch_ports_disabled(struct drm_i915_private *dev_priv,
 	assert_pch_hdmi_disabled(dev_priv, pipe, PCH_HDMID);
 }
 
+static void intel_init_dpio(struct drm_device *dev)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+
+	if (!IS_VALLEYVIEW(dev))
+		return;
+
+	/*
+	 * From VLV2A0_DP_eDP_DPIO_driver_vbios_notes_10.docx -
+	 *  6.	De-assert cmn_reset/side_reset. Same as VLV X0.
+	 *   a.	GUnit 0x2110 bit[0] set to 1 (def 0)
+	 *   b.	The other bits such as sfr settings / modesel may all be set
+	 *      to 0.
+	 *
+	 * This should only be done on init and resume from S3 with both
+	 * PLLs disabled, or we risk losing DPIO and PLL synchronization.
+	 */
+	I915_WRITE(DPIO_CTL, I915_READ(DPIO_CTL) | DPIO_CMNRST);
+}
+
 static void vlv_enable_pll(struct intel_crtc *crtc)
 {
 	struct drm_device *dev = crtc->base.dev;
@@ -10370,6 +10390,8 @@ void intel_modeset_init_hw(struct drm_device *dev)
 		I915_WRITE(DPLL(PIPE_B), I915_READ(DPLL(PIPE_B)) |
 			   DPLL_INTEGRATED_CRI_CLK_VLV);
 
+	intel_init_dpio(dev);
+
 	mutex_lock(&dev->struct_mutex);
 	intel_enable_gt_powersave(dev);
 	mutex_unlock(&dev->struct_mutex);