drm/i915/tv: Poll for DAC state change

Instead of sleeping for an arbitrary length of time (the documentation
fails to specify how long to wait for) wait until the load detection has
changed state (or at most the 20ms as before).
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

drivers/gpu/drm/i915/intel_tv.c

@@ -1234,9 +1234,7 @@ intel_tv_detect_type (struct intel_tv *intel_tv)
 	unsigned long irqflags;
 	u32 tv_ctl, save_tv_ctl;
 	u32 tv_dac, save_tv_dac;
-	int type = DRM_MODE_CONNECTOR_Unknown;
-
-	tv_dac = I915_READ(TV_DAC);
+	int type;
 
 	/* Disable TV interrupts around load detect or we'll recurse */
 	spin_lock_irqsave(&dev_priv->user_irq_lock, irqflags);
@@ -1244,19 +1242,14 @@ intel_tv_detect_type (struct intel_tv *intel_tv)
 			      PIPE_HOTPLUG_TV_INTERRUPT_ENABLE);
 	spin_unlock_irqrestore(&dev_priv->user_irq_lock, irqflags);
 
-	/*
-	 * Detect TV by polling)
-	 */
-	save_tv_dac = tv_dac;
-	tv_ctl = I915_READ(TV_CTL);
-	save_tv_ctl = tv_ctl;
-	tv_ctl &= ~TV_ENC_ENABLE;
-	tv_ctl &= ~TV_TEST_MODE_MASK;
+	save_tv_dac = tv_dac = I915_READ(TV_DAC);
+	save_tv_ctl = tv_ctl = I915_READ(TV_CTL);
+
+	/* Poll for TV detection */
+	tv_ctl &= ~(TV_ENC_ENABLE | TV_TEST_MODE_MASK);
 	tv_ctl |= TV_TEST_MODE_MONITOR_DETECT;
-	tv_dac &= ~TVDAC_SENSE_MASK;
-	tv_dac &= ~DAC_A_MASK;
-	tv_dac &= ~DAC_B_MASK;
-	tv_dac &= ~DAC_C_MASK;
+
+	tv_dac &= ~(TVDAC_SENSE_MASK | DAC_A_MASK | DAC_B_MASK | DAC_C_MASK);
 	tv_dac |= (TVDAC_STATE_CHG_EN |
 		   TVDAC_A_SENSE_CTL |
 		   TVDAC_B_SENSE_CTL |
@@ -1265,37 +1258,37 @@ intel_tv_detect_type (struct intel_tv *intel_tv)
 		   DAC_A_0_7_V |
 		   DAC_B_0_7_V |
 		   DAC_C_0_7_V);
+
 	I915_WRITE(TV_CTL, tv_ctl);
 	I915_WRITE(TV_DAC, tv_dac);
 	POSTING_READ(TV_DAC);
-	msleep(20);
-
-	tv_dac = I915_READ(TV_DAC);
-	I915_WRITE(TV_DAC, save_tv_dac);
-	I915_WRITE(TV_CTL, save_tv_ctl);
-	POSTING_READ(TV_CTL);
-	msleep(20);
 
-	/*
-	 *  A B C
-	 *  0 1 1 Composite
-	 *  1 0 X svideo
-	 *  0 0 0 Component
-	 */
-	if ((tv_dac & TVDAC_SENSE_MASK) == (TVDAC_B_SENSE | TVDAC_C_SENSE)) {
-		DRM_DEBUG_KMS("Detected Composite TV connection\n");
-		type = DRM_MODE_CONNECTOR_Composite;
-	} else if ((tv_dac & (TVDAC_A_SENSE|TVDAC_B_SENSE)) == TVDAC_A_SENSE) {
-		DRM_DEBUG_KMS("Detected S-Video TV connection\n");
-		type = DRM_MODE_CONNECTOR_SVIDEO;
-	} else if ((tv_dac & TVDAC_SENSE_MASK) == 0) {
-		DRM_DEBUG_KMS("Detected Component TV connection\n");
-		type = DRM_MODE_CONNECTOR_Component;
-	} else {
-		DRM_DEBUG_KMS("No TV connection detected\n");
-		type = -1;
+	type = -1;
+	if (wait_for((tv_dac = I915_READ(TV_DAC)) & TVDAC_STATE_CHG, 20) == 0) {
+		/*
+		 *  A B C
+		 *  0 1 1 Composite
+		 *  1 0 X svideo
+		 *  0 0 0 Component
+		 */
+		if ((tv_dac & TVDAC_SENSE_MASK) == (TVDAC_B_SENSE | TVDAC_C_SENSE)) {
+			DRM_DEBUG_KMS("Detected Composite TV connection\n");
+			type = DRM_MODE_CONNECTOR_Composite;
+		} else if ((tv_dac & (TVDAC_A_SENSE|TVDAC_B_SENSE)) == TVDAC_A_SENSE) {
+			DRM_DEBUG_KMS("Detected S-Video TV connection\n");
+			type = DRM_MODE_CONNECTOR_SVIDEO;
+		} else if ((tv_dac & TVDAC_SENSE_MASK) == 0) {
+			DRM_DEBUG_KMS("Detected Component TV connection\n");
+			type = DRM_MODE_CONNECTOR_Component;
+		} else {
+			DRM_DEBUG_KMS("Unrecognised TV connection: %x\n",
+				      tv_dac);
+		}
 	}
 
+	I915_WRITE(TV_DAC, save_tv_dac & ~TVDAC_STATE_CHG_EN);
+	I915_WRITE(TV_CTL, save_tv_ctl);
+
 	/* Restore interrupt config */
 	spin_lock_irqsave(&dev_priv->user_irq_lock, irqflags);
 	i915_enable_pipestat(dev_priv, 0, PIPE_HOTPLUG_INTERRUPT_ENABLE |