drm/i915: Add module param to test the load detect code

This is useful for writing igts to make sure we don't break this,
without being forced to own a one of these dinosaurs.

Suggested-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Cc: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Reviewed-by: Ander Conselvan de Oliveira <conselvan2@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_drv.h

@@ -2462,6 +2462,7 @@ struct i915_params {
 	bool enable_hangcheck;
 	bool fastboot;
 	bool prefault_disable;
+	bool load_detect_test;
 	bool reset;
 	bool disable_display;
 	bool disable_vtd_wa;

drivers/gpu/drm/i915/i915_params.c

@@ -43,6 +43,7 @@ struct i915_params i915 __read_mostly = {
 	.enable_ips = 1,
 	.fastboot = 0,
 	.prefault_disable = 0,
+	.load_detect_test = 0,
 	.reset = true,
 	.invert_brightness = 0,
 	.disable_display = 0,
@@ -139,11 +140,16 @@ module_param_named(fastboot, i915.fastboot, bool, 0600);
 MODULE_PARM_DESC(fastboot,
 	"Try to skip unnecessary mode sets at boot time (default: false)");
 
-module_param_named(prefault_disable, i915.prefault_disable, bool, 0600);
+module_param_named_unsafe(prefault_disable, i915.prefault_disable, bool, 0600);
 MODULE_PARM_DESC(prefault_disable,
 	"Disable page prefaulting for pread/pwrite/reloc (default:false). "
 	"For developers only.");
 
+module_param_named_unsafe(load_detect_test, i915.load_detect_test, bool, 0600);
+MODULE_PARM_DESC(load_detect_test,
+	"Force-enable the VGA load detect code for testing (default:false). "
+	"For developers only.");
+
 module_param_named(invert_brightness, i915.invert_brightness, int, 0600);
 MODULE_PARM_DESC(invert_brightness,
 	"Invert backlight brightness "

drivers/gpu/drm/i915/intel_crt.c

@@ -690,7 +690,7 @@ intel_crt_detect(struct drm_connector *connector, bool force)
 	 * broken monitor (without edid) to work behind a broken kvm (that fails
 	 * to have the right resistors for HP detection) needs to fix this up.
 	 * For now just bail out. */
-	if (I915_HAS_HOTPLUG(dev)) {
+	if (I915_HAS_HOTPLUG(dev) && !i915.load_detect_test) {
 		status = connector_status_disconnected;
 		goto out;
 	}
@@ -706,8 +706,10 @@ intel_crt_detect(struct drm_connector *connector, bool force)
 	if (intel_get_load_detect_pipe(connector, NULL, &tmp, &ctx)) {
 		if (intel_crt_detect_ddc(connector))
 			status = connector_status_connected;
-		else
+		else if (INTEL_INFO(dev)->gen < 4)
 			status = intel_crt_load_detect(crt);
+		else
+			status = connector_status_unknown;
 		intel_release_load_detect_pipe(connector, &tmp, &ctx);
 	} else
 		status = connector_status_unknown;