drm/i915: resurrect panel lid handling

But disabled by default. This essentially reverts

commit bcd5023c961a44c7149936553b6929b2b233dd27
Author: Dave Airlie <airlied@redhat.com>
Date:   Mon Mar 14 14:17:55 2011 +1000

    drm/i915: disable opregion lid detection for now

but leaves the autodetect mode disabled. There's also the explicit lid
status option added in

commit fca874092597ef946b8f07031d8c31c58b212144
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date:   Thu Feb 17 13:44:48 2011 +0000

    drm/i915: Add a module parameter to ignore lid status

Which overloaded the meaning for the panel_ignore_lid parameter even
more. To fix up this mess, give the non-negative numbers 0,1 the
original meaning back and use negative numbers to force a given state.
So now we have

1  - disable autodetect, return unknown
0  - enable autodetect
-1 - force to disconnected/lid closed
-2 - force to connected/lid open

v2: My C programmer license has been revoked ...

v3: Beautify the code a bit, as suggested by Chris Wilson.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=27622
Tested-by: Andreas Sturmlechner <andreas.sturmlechner@gmail.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_drv.c

@@ -47,11 +47,11 @@ MODULE_PARM_DESC(modeset,
 unsigned int i915_fbpercrtc __always_unused = 0;
 module_param_named(fbpercrtc, i915_fbpercrtc, int, 0400);
 
-int i915_panel_ignore_lid __read_mostly = 0;
+int i915_panel_ignore_lid __read_mostly = 1;
 module_param_named(panel_ignore_lid, i915_panel_ignore_lid, int, 0600);
 MODULE_PARM_DESC(panel_ignore_lid,
-		"Override lid status (0=autodetect [default], 1=lid open, "
-		"-1=lid closed)");
+		"Override lid status (0=autodetect, 1=autodetect disabled [default], "
+		"-1=force lid closed, -2=force lid open)");
 
 unsigned int i915_powersave __read_mostly = 1;
 module_param_named(powersave, i915_powersave, int, 0600);

drivers/gpu/drm/i915/intel_panel.c

@@ -275,7 +275,7 @@ static void intel_panel_actually_set_backlight(struct drm_device *dev, u32 level
 	}
 
 	tmp = I915_READ(BLC_PWM_CTL);
-	if (INTEL_INFO(dev)->gen < 4) 
+	if (INTEL_INFO(dev)->gen < 4)
 		level <<= 1;
 	tmp &= ~BACKLIGHT_DUTY_CYCLE_MASK;
 	I915_WRITE(BLC_PWM_CTL, tmp | level);
@@ -374,26 +374,23 @@ static void intel_panel_init_backlight(struct drm_device *dev)
 enum drm_connector_status
 intel_panel_detect(struct drm_device *dev)
 {
-#if 0
 	struct drm_i915_private *dev_priv = dev->dev_private;
-#endif
-
-	if (i915_panel_ignore_lid)
-		return i915_panel_ignore_lid > 0 ?
-			connector_status_connected :
-			connector_status_disconnected;
 
-	/* opregion lid state on HP 2540p is wrong at boot up,
-	 * appears to be either the BIOS or Linux ACPI fault */
-#if 0
 	/* Assume that the BIOS does not lie through the OpRegion... */
-	if (dev_priv->opregion.lid_state)
+	if (!i915_panel_ignore_lid && dev_priv->opregion.lid_state) {
 		return ioread32(dev_priv->opregion.lid_state) & 0x1 ?
 			connector_status_connected :
 			connector_status_disconnected;
-#endif
+	}
 
-	return connector_status_unknown;
+	switch (i915_panel_ignore_lid) {
+	case -2:
+		return connector_status_connected;
+	case -1:
+		return connector_status_disconnected;
+	default:
+		return connector_status_unknown;
+	}
 }
 
 #ifdef CONFIG_BACKLIGHT_CLASS_DEVICE