[PATCH] drm/xe/display: fix oops in suspend/shutdown without display

[Jani Nikula <jani.nikula@intel.com>]

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 44e694958b95
("drm/xe/display: Implement display support"), but the oops was likely
introduced later at commit ddf6492e0e50 ("drm/xe/display: Make display
suspend/resume work on discrete").

Fixes: 44e694958b95 ("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+
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
---
 drivers/gpu/drm/xe/display/xe_display.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/xe/display/xe_display.c b/drivers/gpu/drm/xe/display/xe_display.c
index 053abd6f6514..5f25932730f4 100644
--- a/drivers/gpu/drm/xe/display/xe_display.c
+++ b/drivers/gpu/drm/xe/display/xe_display.c
@@ -104,6 +104,15 @@ 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);
 
@@ -117,8 +126,6 @@ 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;
-- 
2.47.3