drm/i915/gsc: mei interrupt top half should be in irq disabled context

MEI GSC interrupt comes from i915. It has top half and bottom half.
Top half is called from i915 interrupt handler. It should be in
irq disabled context.

With RT kernel, by default i915 IRQ handler is in threaded IRQ. MEI GSC
top half might be in threaded IRQ context. generic_handle_irq_safe API
could be called from either IRQ or process context, it disables local
IRQ then calls MEI GSC interrupt top half.

This change fixes A380/A770 GPU boot hang issue with RT kernel.

Fixes: 1e3dc1d ("drm/i915/gsc: add gsc as a mei auxiliary device")
Tested-by: Furong Zhou <[email protected]>
Suggested-by: Sebastian Andrzej Siewior <[email protected]>
Acked-by: Sebastian Andrzej Siewior <[email protected]>
Signed-off-by: Junxiao Chang <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Reviewed-by: Rodrigo Vivi <[email protected]>
Signed-off-by: Rodrigo Vivi <[email protected]>
(cherry picked from commit dccf655f69002d496a527ba441b4f008aa5bebbf)
Signed-off-by: Joonas Lahtinen <[email protected]>

Author: junxiaoc

drivers/gpu/drm/i915/gt/intel_gsc.c

@@ -284,7 +284,7 @@ static void gsc_irq_handler(struct intel_gt *gt, unsigned int intf_id)
 	if (gt->gsc.intf[intf_id].irq < 0)
 		return;
 
-	ret = generic_handle_irq(gt->gsc.intf[intf_id].irq);
+	ret = generic_handle_irq_safe(gt->gsc.intf[intf_id].irq);
 	if (ret)
 		gt_err_ratelimited(gt, "error handling GSC irq: %d\n", ret);
 }