drm/i915: Add support for VGA load detection (pre-945).

Two approaches for VGA detections: hot plug detection for 945G onwards
and load pipe detection for Pre-945G.  Load pipe detection will get one free
pipe, set border color as red and blue, then check CRT status by
swf register.  This is a sync-up with the 2D driver.
Signed-off-by: Ma Ling <ling.ma@intel.com>
Signed-off-by: Eric Anholt <eric@anholt.net>

drivers/gpu/drm/i915/intel_crt.c

@@ -198,9 +198,142 @@ static bool intel_crt_detect_ddc(struct drm_connector *connector)
 	return intel_ddc_probe(intel_output);
 }
 
+static enum drm_connector_status
+intel_crt_load_detect(struct drm_crtc *crtc, struct intel_output *intel_output)
+{
+	struct drm_encoder *encoder = &intel_output->enc;
+	struct drm_device *dev = encoder->dev;
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
+	uint32_t pipe = intel_crtc->pipe;
+	uint32_t save_bclrpat;
+	uint32_t save_vtotal;
+	uint32_t vtotal, vactive;
+	uint32_t vsample;
+	uint32_t vblank, vblank_start, vblank_end;
+	uint32_t dsl;
+	uint32_t bclrpat_reg;
+	uint32_t vtotal_reg;
+	uint32_t vblank_reg;
+	uint32_t vsync_reg;
+	uint32_t pipeconf_reg;
+	uint32_t pipe_dsl_reg;
+	uint8_t	st00;
+	enum drm_connector_status status;
+
+	if (pipe == 0) {
+		bclrpat_reg = BCLRPAT_A;
+		vtotal_reg = VTOTAL_A;
+		vblank_reg = VBLANK_A;
+		vsync_reg = VSYNC_A;
+		pipeconf_reg = PIPEACONF;
+		pipe_dsl_reg = PIPEADSL;
+	} else {
+		bclrpat_reg = BCLRPAT_B;
+		vtotal_reg = VTOTAL_B;
+		vblank_reg = VBLANK_B;
+		vsync_reg = VSYNC_B;
+		pipeconf_reg = PIPEBCONF;
+		pipe_dsl_reg = PIPEBDSL;
+	}
+
+	save_bclrpat = I915_READ(bclrpat_reg);
+	save_vtotal = I915_READ(vtotal_reg);
+	vblank = I915_READ(vblank_reg);
+
+	vtotal = ((save_vtotal >> 16) & 0xfff) + 1;
+	vactive = (save_vtotal & 0x7ff) + 1;
+
+	vblank_start = (vblank & 0xfff) + 1;
+	vblank_end = ((vblank >> 16) & 0xfff) + 1;
+
+	/* Set the border color to purple. */
+	I915_WRITE(bclrpat_reg, 0x500050);
+
+	if (IS_I9XX(dev)) {
+		uint32_t pipeconf = I915_READ(pipeconf_reg);
+		I915_WRITE(pipeconf_reg, pipeconf | PIPECONF_FORCE_BORDER);
+		/* Wait for next Vblank to substitue
+		 * border color for Color info */
+		intel_wait_for_vblank(dev);
+		st00 = I915_READ8(VGA_MSR_WRITE);
+		status = ((st00 & (1 << 4)) != 0) ?
+			connector_status_connected :
+			connector_status_disconnected;
+
+		I915_WRITE(pipeconf_reg, pipeconf);
+	} else {
+		bool restore_vblank = false;
+		int count, detect;
+
+		/*
+		* If there isn't any border, add some.
+		* Yes, this will flicker
+		*/
+		if (vblank_start <= vactive && vblank_end >= vtotal) {
+			uint32_t vsync = I915_READ(vsync_reg);
+			uint32_t vsync_start = (vsync & 0xffff) + 1;
+
+			vblank_start = vsync_start;
+			I915_WRITE(vblank_reg,
+				   (vblank_start - 1) |
+				   ((vblank_end - 1) << 16));
+			restore_vblank = true;
+		}
+		/* sample in the vertical border, selecting the larger one */
+		if (vblank_start - vactive >= vtotal - vblank_end)
+			vsample = (vblank_start + vactive) >> 1;
+		else
+			vsample = (vtotal + vblank_end) >> 1;
+
+		/*
+		 * Wait for the border to be displayed
+		 */
+		while (I915_READ(pipe_dsl_reg) >= vactive)
+			;
+		while ((dsl = I915_READ(pipe_dsl_reg)) <= vsample)
+			;
+		/*
+		 * Watch ST00 for an entire scanline
+		 */
+		detect = 0;
+		count = 0;
+		do {
+			count++;
+			/* Read the ST00 VGA status register */
+			st00 = I915_READ8(VGA_MSR_WRITE);
+			if (st00 & (1 << 4))
+				detect++;
+		} while ((I915_READ(pipe_dsl_reg) == dsl));
+
+		/* restore vblank if necessary */
+		if (restore_vblank)
+			I915_WRITE(vblank_reg, vblank);
+		/*
+		 * If more than 3/4 of the scanline detected a monitor,
+		 * then it is assumed to be present. This works even on i830,
+		 * where there isn't any way to force the border color across
+		 * the screen
+		 */
+		status = detect * 4 > count * 3 ?
+			 connector_status_connected :
+			 connector_status_disconnected;
+	}
+
+	/* Restore previous settings */
+	I915_WRITE(bclrpat_reg, save_bclrpat);
+
+	return status;
+}
+
 static enum drm_connector_status intel_crt_detect(struct drm_connector *connector)
 {
 	struct drm_device *dev = connector->dev;
+	struct intel_output *intel_output = to_intel_output(connector);
+	struct drm_encoder *encoder = &intel_output->enc;
+	struct drm_crtc *crtc;
+	int dpms_mode;
+	enum drm_connector_status status;
 
 	if (IS_I9XX(dev) && !IS_I915G(dev) && !IS_I915GM(dev)) {
 		if (intel_crt_detect_hotplug(connector))
@@ -212,8 +345,20 @@ static enum drm_connector_status intel_crt_detect(struct drm_connector *connecto
 	if (intel_crt_detect_ddc(connector))
 		return connector_status_connected;
 
-	/* TODO use load detect */
-	return connector_status_unknown;
+	/* for pre-945g platforms use load detect */
+	if (encoder->crtc && encoder->crtc->enabled) {
+		status = intel_crt_load_detect(encoder->crtc, intel_output);
+	} else {
+		crtc = intel_get_load_detect_pipe(intel_output,
+						  NULL, &dpms_mode);
+		if (crtc) {
+			status = intel_crt_load_detect(crtc, intel_output);
+			intel_release_load_detect_pipe(intel_output, dpms_mode);
+		} else
+			status = connector_status_unknown;
+	}
+
+	return status;
 }
 
 static void intel_crt_destroy(struct drm_connector *connector)