VGA: Detect analog monitors differently from digital monitors

If a display is connected only to the DVI port, it can be
"accidentally" detected as both DVI and analog VGA.  If EDID is
supported, determine whether the EDID block says the monitor is
digital.  If EDID is not supported, do some voodoo to determine if
there is a monitor load present.

1 files changed, 114 insertions, 4 deletions

diff --git a/src/xg47_outputs.c b/src/xg47_outputs.c
index d13ecfc..6454d61 100644
--- a/src/xg47_outputs.c
+++ b/src/xg47_outputs.c
@@ -55,7 +55,8 @@ static void xg47_output_mode_set(xf86OutputPtr output, DisplayModePtr mode,
 static void xg47_vga_dpms(xf86OutputPtr output, int mode);
 static void xg47_dvi_dpms(xf86OutputPtr output, int mode);
 
-static xf86OutputStatus xg47_output_detect(xf86OutputPtr output);
+static xf86OutputStatus xg47_vga_detect(xf86OutputPtr output);
+static xf86OutputStatus xg47_dvi_detect(xf86OutputPtr output);
 
 static void xg47_output_save(xf86OutputPtr output);
 
@@ -78,7 +79,7 @@ static const xf86OutputFuncsRec xg47_vga_funcs = {
     .prepare = xg47_output_prepare,
     .mode_set = xg47_output_mode_set,
     .commit = xg47_output_commit,
-    .detect = xg47_output_detect,
+    .detect = xg47_vga_detect,
     .get_modes = xg47_output_get_modes,
     .destroy = xg47_output_destroy
 };
@@ -93,7 +94,7 @@ static const xf86OutputFuncsRec xg47_dvi_funcs = {
     .prepare = xg47_output_prepare,
     .mode_set = xg47_output_mode_set,
     .commit = xg47_output_commit,
-    .detect = xg47_output_detect,
+    .detect = xg47_dvi_detect,
     .get_modes = xg47_output_get_modes,
     .destroy = xg47_output_destroy
 };
@@ -145,8 +146,117 @@ xg47_dvi_dpms(xf86OutputPtr output, int mode)
 }
 
 
+void delay4I2C(XGIPtr pXGI, unsigned times)
+{
+    unsigned i;
+
+    for (i = 0; i < (0x40 * times); i++) {
+	(void) INB(0x3c4);
+	(void) INB(0x3c4);
+    }
+}
+
+
+/**
+ * Wait for vertical retrace on specified CRT
+ *
+ * \param pXGI  Device information handle
+ * \param crt   0 for first CRT, 1 for second CRT
+ */
+void waitVerticalRetrace(XGIPtr pXGI, int crt)
+{
+    const unsigned pattern = (crt == 0) ? 0x08 : 0x80;
+    unsigned i;
+
+    (void) INB(0x3DA);
+
+    for(i = 0; i < 0xFFFFU; i++) {
+        const uint8_t sync = INB(0x3DA);
+        if (sync & pattern)
+            return;
+    }
+}
+
+
+xf86OutputStatus
+xg47_vga_detect(xf86OutputPtr output)
+{
+    XGIPtr pXGI = XGIPTR(output->scrn);
+    struct xg47_crtc_private *xg47_output = 
+	(struct xg47_crtc_private *) output->driver_private;
+    I2CDevPtr i2c_dev;
+    Bool attached;
+
+
+    /* See if there is a display attached that returns an EDID block.
+     */
+    i2c_dev = xf86I2CFindDev(xg47_output->pI2C, 0xA0);
+    if (i2c_dev != NULL) {
+	I2CByte data;
+
+	/* If bit 7 of byte 14 is set, then the attached device is digital.
+	 * This means that it's not an analog CRT.
+	 */
+	xf86I2CReadByte(i2c_dev, 14, &data);
+	attached = ((data & 0x80) == 0);
+    } else {
+	uint8_t seq_24;
+	uint8_t seq_25;
+	uint8_t seq_69;
+
+
+	/* Enable the DAC.
+	 */
+	seq_24 = IN3C5B(0x24);
+	OUT3C5B(0x24, seq_24 | 0x01);
+
+
+	/* Wait for the vertical refresh period.
+	 */
+	waitVerticalRetrace(pXGI, 0);
+
+
+	/* 3c5.68-69 - Monitor sensing control register for CRT1
+	 *    15: Monitor sensing enable
+	 * 14:13: reserved
+	 *    12: scheme 
+	 *        1: apply monitor sensing data during blanking
+	 *        0: apply monitor sensing data all the time
+	 * 11:10: reserved
+	 *   9:0: monitor sensing data
+	 *
+	 * Registers 6B-6A have the same meaning for CRT2
+	 */
+	seq_69 = IN3C5B(0x69);
+	OUT3C5B(0x69, seq_69 | 0x80);
+	
+
+	delay4I2C(pXGI, 300);
+	waitVerticalRetrace(pXGI, 0);
+
+
+	/* 3c5.25 - Monitor sensing register
+	 *    7: DAC2 sensing status after anti-jitter filtering.
+	 *  6:4: DAC2 red/green/blue sensing status
+	 *    3: DAC1 sensing status after anti-jitter filtering.
+	 *  2:0: DAC1 red/green/blue sensing status
+	 */
+	seq_25 = IN3C5B(0x25);
+	attached = ((seq_25 & 0x08) != 0);
+
+
+	/* Restore modified values.
+	 */
+	OUT3C5B(0x24, seq_24);
+	OUT3C5B(0x69, seq_69 & ~0x80);
+    }
+
+    return (attached) ? XF86OutputStatusConnected : XF86OutputStatusUnknown;
+}
+
+
 xf86OutputStatus
-xg47_output_detect(xf86OutputPtr output)
+xg47_dvi_detect(xf86OutputPtr output)
 {
     struct xg47_crtc_private *xg47_output = 
 	(struct xg47_crtc_private *) output->driver_private;