drm/i915: Acquire dpio_lock for VLV sideband programming in DP/HDMI

Otherwise we get flooded by the kernel warning us that we are doing
long sequences of IO without serialisation. For example,

 WARNING: CPU: 0 PID: 11136 at drivers/gpu/drm/i915/intel_sideband.c:40 vlv_sideband_rw+0x48/0x1ef()
 Modules linked in:
 CPU: 0 PID: 11136 Comm: kworker/u2:0 Tainted: G        W    3.11.0-rc2+ #4
 Call Trace:
  [<c2028564>] ?  warn_slowpath_common+0x63/0x78
  [<c227ad43>] ?  vlv_sideband_rw+0x48/0x1ef
  [<c20285dd>] ?  warn_slowpath_null+0xf/0x13
  [<c227ad43>] ?  vlv_sideband_rw+0x48/0x1ef
  [<c227b060>] ?  vlv_dpio_write+0x1c/0x21
  [<c2262b3b>] ?  intel_dp_set_signal_levels+0x24a/0x385
  [<c2264909>] ?  intel_dp_complete_link_train+0x25/0x1d1
  [<c2264c55>] ?  intel_dp_check_link_status+0xf7/0x106
  [<c2238ced>] ?  i915_hotplug_work_func+0x17b/0x221
  [<c203a204>] ?  process_one_work+0x12e/0x210
  [<c203a5e4>] ?  worker_thread+0x116/0x1ad
  [<c203a4ce>] ?  rescuer_thread+0x1cb/0x1cb
  [<c203d8f5>] ?  kthread+0x67/0x6c
  [<c2457ebb>] ?  ret_from_kernel_thread+0x1b/0x30
  [<c203d88e>] ?  init_completion+0x18/0x18

v2: Retire the locking in vlv_crtc_enable() and do it close to the meat.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
[danvet: Squash in a s/mutex_lock/mutex_unlock/ fixup spotted by the 0
day kernel build/coccinelle and reported by Dan Carpenter.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_display.c

@@ -3652,8 +3652,6 @@ static void valleyview_crtc_enable(struct drm_crtc *crtc)
 	intel_crtc->active = true;
 	intel_update_watermarks(dev);
 
-	mutex_lock(&dev_priv->dpio_lock);
-
 	for_each_encoder_on_crtc(dev, crtc, encoder)
 		if (encoder->pre_pll_enable)
 			encoder->pre_pll_enable(encoder);
@@ -3678,8 +3676,6 @@ static void valleyview_crtc_enable(struct drm_crtc *crtc)
 	intel_crtc_update_cursor(crtc, true);
 
 	intel_update_fbc(dev);
-
-	mutex_unlock(&dev_priv->dpio_lock);
 }
 
 static void i9xx_crtc_enable(struct drm_crtc *crtc)

drivers/gpu/drm/i915/intel_dp.c

@@ -1727,6 +1727,7 @@ static void intel_pre_enable_dp(struct intel_encoder *encoder)
 		int pipe = intel_crtc->pipe;
 		u32 val;
 
+		mutex_lock(&dev_priv->dpio_lock);
 		val = vlv_dpio_read(dev_priv, DPIO_DATA_LANE_A(port));
 		val = 0;
 		if (pipe)
@@ -1740,6 +1741,7 @@ static void intel_pre_enable_dp(struct intel_encoder *encoder)
 				 0x00760018);
 		vlv_dpio_write(dev_priv, DPIO_PCS_CLOCKBUF8(port),
 				 0x00400888);
+		mutex_unlock(&dev_priv->dpio_lock);
 	}
 }
 
@@ -1754,6 +1756,7 @@ static void intel_dp_pre_pll_enable(struct intel_encoder *encoder)
 		return;
 
 	/* Program Tx lane resets to default */
+	mutex_lock(&dev_priv->dpio_lock);
 	vlv_dpio_write(dev_priv, DPIO_PCS_TX(port),
 			 DPIO_PCS_TX_LANE2_RESET |
 			 DPIO_PCS_TX_LANE1_RESET);
@@ -1767,6 +1770,7 @@ static void intel_dp_pre_pll_enable(struct intel_encoder *encoder)
 	vlv_dpio_write(dev_priv, DPIO_PCS_STAGGER1(port), 0x00750f00);
 	vlv_dpio_write(dev_priv, DPIO_TX_CTL(port), 0x00001500);
 	vlv_dpio_write(dev_priv, DPIO_TX_LANE(port), 0x40400000);
+	mutex_unlock(&dev_priv->dpio_lock);
 }
 
 /*
@@ -1978,6 +1982,7 @@ static uint32_t intel_vlv_signal_levels(struct intel_dp *intel_dp)
 		return 0;
 	}
 
+	mutex_lock(&dev_priv->dpio_lock);
 	vlv_dpio_write(dev_priv, DPIO_TX_OCALINIT(port), 0x00000000);
 	vlv_dpio_write(dev_priv, DPIO_TX_SWING_CTL4(port), demph_reg_value);
 	vlv_dpio_write(dev_priv, DPIO_TX_SWING_CTL2(port),
@@ -1986,6 +1991,7 @@ static uint32_t intel_vlv_signal_levels(struct intel_dp *intel_dp)
 	vlv_dpio_write(dev_priv, DPIO_PCS_STAGGER0(port), 0x00030000);
 	vlv_dpio_write(dev_priv, DPIO_PCS_CTL_OVER1(port), preemph_reg_value);
 	vlv_dpio_write(dev_priv, DPIO_TX_OCALINIT(port), 0x80000000);
+	mutex_unlock(&dev_priv->dpio_lock);
 
 	return 0;
 }

drivers/gpu/drm/i915/intel_hdmi.c

@@ -1019,6 +1019,7 @@ static void intel_hdmi_pre_enable(struct intel_encoder *encoder)
 		return;
 
 	/* Enable clock channels for this port */
+	mutex_lock(&dev_priv->dpio_lock);
 	val = vlv_dpio_read(dev_priv, DPIO_DATA_LANE_A(port));
 	val = 0;
 	if (pipe)
@@ -1049,6 +1050,7 @@ static void intel_hdmi_pre_enable(struct intel_encoder *encoder)
 			 0x00760018);
 	vlv_dpio_write(dev_priv, DPIO_PCS_CLOCKBUF8(port),
 			 0x00400888);
+	mutex_unlock(&dev_priv->dpio_lock);
 }
 
 static void intel_hdmi_pre_pll_enable(struct intel_encoder *encoder)
@@ -1062,6 +1064,7 @@ static void intel_hdmi_pre_pll_enable(struct intel_encoder *encoder)
 		return;
 
 	/* Program Tx lane resets to default */
+	mutex_lock(&dev_priv->dpio_lock);
 	vlv_dpio_write(dev_priv, DPIO_PCS_TX(port),
 			 DPIO_PCS_TX_LANE2_RESET |
 			 DPIO_PCS_TX_LANE1_RESET);
@@ -1080,6 +1083,7 @@ static void intel_hdmi_pre_pll_enable(struct intel_encoder *encoder)
 			 0x00002000);
 	vlv_dpio_write(dev_priv, DPIO_TX_OCALINIT(port),
 			 DPIO_TX_OCALINIT_EN);
+	mutex_unlock(&dev_priv->dpio_lock);
 }
 
 static void intel_hdmi_post_disable(struct intel_encoder *encoder)