drm/xe/guc: Make creation of SLPC debugfs files conditional

Platforms that do not support SLPC are exempted from the GuC PC support.
The GuC PC does not get initialized, and neither do its BOs get created.

This causes a problem because the GuC PC debugfs file is still being
created. Whenever the file is attempted to read, it causes a NULL
pointer dereference on the supposed BO of the GuC PC.

So, make the creation of SLPC debugfs files conditional to when SLPC
features are supported.

Fixes: aaab5404b16f ("drm/xe: Introduce GuC PC debugfs")
Suggested-by: Matt Roper <[e-mail]>
Reviewed-by: Tejas Upadhyay <[e-mail]>
Reviewed-by: Stuart Summers <[e-mail]>
Signed-off-by: Aradhya Bhatia <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Matt Roper <[e-mail]>
(cherry picked from commit 17486cf3df5320752cc67ee8bcb2379d1b9de76c)
Signed-off-by: Thomas Hellström <[e-mail]>

drivers/gpu/drm/xe/xe_guc_debugfs.c

···
 	{ "guc_ctb", .show = guc_debugfs_show, .data = guc_ctb },
 };
 
+/* For GuC debugfs files that require the SLPC support */
+static const struct drm_info_list slpc_debugfs_list[] = {
+	{ "guc_pc", .show = guc_debugfs_show, .data = guc_pc },
+};
+
 /* everything else should be added here */
 static const struct drm_info_list pf_only_debugfs_list[] = {
 	{ "guc_log", .show = guc_debugfs_show, .data = guc_log },
 	{ "guc_log_dmesg", .show = guc_debugfs_show, .data = guc_log_dmesg },
-	{ "guc_pc", .show = guc_debugfs_show, .data = guc_pc },
 };
 
 void xe_guc_debugfs_register(struct xe_guc *guc, struct dentry *parent)
 {
-	struct drm_minor *minor = guc_to_xe(guc)->drm.primary;
+	struct xe_device *xe =  guc_to_xe(guc);
+	struct drm_minor *minor = xe->drm.primary;
 
 	drm_debugfs_create_files(vf_safe_debugfs_list,
 				 ARRAY_SIZE(vf_safe_debugfs_list),
 				 parent, minor);
 
-	if (!IS_SRIOV_VF(guc_to_xe(guc)))
+	if (!IS_SRIOV_VF(xe)) {
 		drm_debugfs_create_files(pf_only_debugfs_list,
 					 ARRAY_SIZE(pf_only_debugfs_list),
 					 parent, minor);
+
+		if (!xe->info.skip_guc_pc)
+			drm_debugfs_create_files(slpc_debugfs_list,
+						 ARRAY_SIZE(slpc_debugfs_list),
+						 parent, minor);
+	}
 }