drm/xe/display: fix oops in suspend/shutdown without display

commit 68938cc upstream.

The xe driver keeps track of whether to probe display, and whether
display hardware is there, using xe->info.probe_display. It gets set to
false if there's no display after intel_display_device_probe(). However,
the display may also be disabled via fuses, detected at a later time in
intel_display_device_info_runtime_init().

In this case, the xe driver does for_each_intel_crtc() on uninitialized
mode config in xe_display_flush_cleanup_work(), leading to a NULL
pointer dereference, and generally calls display code with display info
cleared.

Check for intel_display_device_present() after
intel_display_device_info_runtime_init(), and reset
xe->info.probe_display as necessary. Also do unset_display_features()
for completeness, although display runtime init has already done
that. This will need to be unified across all cases later.

Move intel_display_device_info_runtime_init() call slightly earlier,
similar to i915, to avoid a bunch of unnecessary setup for no display
cases.

Note #1: The xe driver has no business doing low level display plumbing
like for_each_intel_crtc() to begin with. It all needs to happen in
display code.

Note #2: The actual bug is present already in commit 44e6949
("drm/xe/display: Implement display support"), but the oops was likely
introduced later at commit ddf6492 ("drm/xe/display: Make display
suspend/resume work on discrete").

Fixes: 44e6949 ("drm/xe/display: Implement display support")
Closes: https://gitlab.freedesktop.org/drm/xe/kernel/-/work_items/7904
Closes: https://gitlab.freedesktop.org/drm/xe/kernel/-/work_items/6150
Cc: stable@vger.kernel.org # v6.8+
Reviewed-by: Suraj Kandpal <suraj.kandpal@intel.com>
Link: https://patch.msgid.link/20260515160920.1082842-1-jani.nikula@intel.com
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
(cherry picked from commit 7c3eb9f)
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: jnikula

drivers/gpu/drm/xe/display/xe_display.c

@@ -109,6 +109,15 @@ int xe_display_init_early(struct xe_device *xe)
 
 	intel_display_driver_early_probe(display);
 
+	intel_display_device_info_runtime_init(display);
+
+	/* Display may have been disabled at runtime init */
+	if (!intel_display_device_present(display)) {
+		xe->info.probe_display = false;
+		unset_display_features(xe);
+		return 0;
+	}
+
 	/* Early display init.. */
 	intel_opregion_setup(display);
 
@@ -122,8 +131,6 @@ int xe_display_init_early(struct xe_device *xe)
 
 	intel_bw_init_hw(display);
 
-	intel_display_device_info_runtime_init(display);
-
 	err = intel_display_driver_probe_noirq(display);
 	if (err)
 		goto err_opregion;