drm/i915: Get rid of the gm45 HPD live state nonsense

The idea that ctg uses different HPD live state bits is
total nonsense, at least on my machine (Dell Latitude
E5400).

The only reason DP-B even works on my ctg is that DP-D
live state is stuck high, even though there is no physical
DP-D port. So when the detect checks DP-B live state it
sees the stuck live state of DP-D instead. If I hack
the driver to not register DP-D at all, and thus we never
enabe DP-D HPD, DP-B stops working as well.

Just to put some conclusive evidence into this mess,
here are the actual hotplug register values for each port:
 Everything disconnected:
                    PORT_HOTPLUG_EN (0x00061110): 0x00000000
                  PORT_HOTPLUG_STAT (0x00061114): 0x00000000
                    PORT_HOTPLUG_EN (0x00061110): 0x08000000
                  PORT_HOTPLUG_STAT (0x00061114): 0x08000000
                    PORT_HOTPLUG_EN (0x00061110): 0x10000000
                  PORT_HOTPLUG_STAT (0x00061114): 0x00000000
                    PORT_HOTPLUG_EN (0x00061110): 0x20000000
                  PORT_HOTPLUG_STAT (0x00061114): 0x00000000
 Only port B connected:
                    PORT_HOTPLUG_EN (0x00061110): 0x00000000
                  PORT_HOTPLUG_STAT (0x00061114): 0x00000000
                    PORT_HOTPLUG_EN (0x00061110): 0x08000000
                  PORT_HOTPLUG_STAT (0x00061114): 0x08000000
                    PORT_HOTPLUG_EN (0x00061110): 0x10000000
                  PORT_HOTPLUG_STAT (0x00061114): 0x00000000
                    PORT_HOTPLUG_EN (0x00061110): 0x20000000
                  PORT_HOTPLUG_STAT (0x00061114): 0x20000000
 Only port C connected:
                    PORT_HOTPLUG_EN (0x00061110): 0x00000000
                  PORT_HOTPLUG_STAT (0x00061114): 0x00000000
                    PORT_HOTPLUG_EN (0x00061110): 0x08000000
                  PORT_HOTPLUG_STAT (0x00061114): 0x08000000
                    PORT_HOTPLUG_EN (0x00061110): 0x10000000
                  PORT_HOTPLUG_STAT (0x00061114): 0x10000000
                    PORT_HOTPLUG_EN (0x00061110): 0x20000000
                  PORT_HOTPLUG_STAT (0x00061114): 0x00000000

So the enable bit and live state bit always match 1:1.
Acked-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230302161013.29213-4-ville.syrjala@linux.intel.com

drivers/gpu/drm/i915/display/g4x_dp.c

@@ -1197,29 +1197,6 @@ static bool g4x_digital_port_connected(struct intel_encoder *encoder)
 	return intel_de_read(dev_priv, PORT_HOTPLUG_STAT) & bit;
 }
 
-static bool gm45_digital_port_connected(struct intel_encoder *encoder)
-{
-	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
-	u32 bit;
-
-	switch (encoder->hpd_pin) {
-	case HPD_PORT_B:
-		bit = PORTB_HOTPLUG_LIVE_STATUS_GM45;
-		break;
-	case HPD_PORT_C:
-		bit = PORTC_HOTPLUG_LIVE_STATUS_GM45;
-		break;
-	case HPD_PORT_D:
-		bit = PORTD_HOTPLUG_LIVE_STATUS_GM45;
-		break;
-	default:
-		MISSING_CASE(encoder->hpd_pin);
-		return false;
-	}
-
-	return intel_de_read(dev_priv, PORT_HOTPLUG_STAT) & bit;
-}
-
 static bool ilk_digital_port_connected(struct intel_encoder *encoder)
 {
 	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
@@ -1384,10 +1361,7 @@ bool g4x_dp_init(struct drm_i915_private *dev_priv,
 	dig_port->hpd_pulse = intel_dp_hpd_pulse;
 
 	if (HAS_GMCH(dev_priv)) {
-		if (IS_GM45(dev_priv))
-			dig_port->connected = gm45_digital_port_connected;
-		else
-			dig_port->connected = g4x_digital_port_connected;
+		dig_port->connected = g4x_digital_port_connected;
 	} else {
 		if (port == PORT_A)
 			dig_port->connected = ilk_digital_port_connected;

drivers/gpu/drm/i915/i915_reg.h

@@ -2379,18 +2379,7 @@
 #define CRT_HOTPLUG_DETECT_VOLTAGE_475MV	(1 << 2)
 
 #define PORT_HOTPLUG_STAT	_MMIO(DISPLAY_MMIO_BASE(dev_priv) + 0x61114)
-/*
- * HDMI/DP bits are g4x+
- *
- * WARNING: Bspec for hpd status bits on gen4 seems to be completely confused.
- * Please check the detailed lore in the commit message for for experimental
- * evidence.
- */
-/* Bspec says GM45 should match G4X/VLV/CHV, but reality disagrees */
-#define   PORTD_HOTPLUG_LIVE_STATUS_GM45	(1 << 29)
-#define   PORTC_HOTPLUG_LIVE_STATUS_GM45	(1 << 28)
-#define   PORTB_HOTPLUG_LIVE_STATUS_GM45	(1 << 27)
-/* G4X/VLV/CHV DP/HDMI bits again match Bspec */
+/* HDMI/DP bits are g4x+ */
 #define   PORTD_HOTPLUG_LIVE_STATUS_G4X		(1 << 27)
 #define   PORTC_HOTPLUG_LIVE_STATUS_G4X		(1 << 28)
 #define   PORTB_HOTPLUG_LIVE_STATUS_G4X		(1 << 29)