intel_idle: Rescan "dead" SMT siblings during initialization

JIRA: https://issues.redhat.com/browse/RHEL-110839

commit a430c11
Author: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Date:   Thu Jun 5 17:06:08 2025 +0200

    intel_idle: Rescan "dead" SMT siblings during initialization

    Make intel_idle_init() call arch_cpu_rescan_dead_smt_siblings() after
    successfully registering intel_idle as the cpuidle driver so as to
    allow the "dead" SMT siblings (if any) to go into deep idle states.

    This is necessary for the processor to be able to reach deep package
    C-states (like PC10) going forward which is requisite for reducing
    power sufficiently in suspend-to-idle, among other things.

    Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
    Tested-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
    Link: https://patch.msgid.link/10669885.nUPlyArG6x@rjwysocki.net

Signed-off-by: Steve Best <sbest@redhat.com>

Author: sfbest

drivers/idle/intel_idle.c

@@ -2476,6 +2476,8 @@ static int __init intel_idle_init(void)
 	pr_debug("Local APIC timer is reliable in %s\n",
 		 boot_cpu_has(X86_FEATURE_ARAT) ? "all C-states" : "C1");
 
+	arch_cpu_rescan_dead_smt_siblings();
+
 	return 0;
 
 hp_setup_fail: