disable vga plane before doing CRT hotplug
---
 src/i830_crt.c |   33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

Index: xf86_video_intel/src/i830_crt.c
===================================================================
--- xf86_video_intel.orig/src/i830_crt.c	2009-08-25 17:20:07.000000000 +0800
+++ xf86_video_intel/src/i830_crt.c	2009-08-31 11:23:59.000000000 +0800
@@ -156,6 +156,38 @@
 
     OUTREG(ADPA, adpa);
 }
+static void
+disable_vga_plane (xf86OutputPtr output)
+{
+    ScrnInfoPtr pScrn = output->scrn;
+    I830Ptr pI830 = I830PTR(pScrn);
+    uint8_t sr01;
+    uint32_t vgadisable;
+
+    vgadisable = INREG(VGACNTRL);
+    if (vgadisable & VGA_DISP_DISABLE)
+	return;
+
+    /*
+     * Bug #17235: G4X machine needs following steps
+     * for disable VGA.
+     * - set bit 5 of SR01;
+     * - Wait 30us;
+     * - disable vga plane;
+     * - restore SR01;
+     */
+	OUTREG8(SRX, 1);
+	sr01 = INREG8(SRX + 1);
+	OUTREG8(SRX + 1, sr01 | (1 << 5));
+	usleep(30);
+
+    OUTREG(VGACNTRL, VGA_DISP_DISABLE);
+    i830WaitForVblank(pScrn);
+
+	OUTREG8(SRX, 1);
+	OUTREG8(SRX + 1, sr01);
+}
+
 
 /**
  * Uses CRT_HOTPLUG_EN and CRT_HOTPLUG_STAT to detect CRT presence.
@@ -176,6 +208,7 @@
     int		tries = 1;
     int		try;
 
+	disable_vga_plane(output);
     /* On 4 series desktop, CRT detect sequence need to be done twice
      * to get a reliable result. */
     if (IS_G4X(pI830) && !IS_GM45(pI830))