irqchip/gic-v3: Handle CPU_PM_ENTER_FAILED correctly

When a CPU attempts to enter low power mode, it disables the redistributor
and Group 1 interrupts and reinitializes the system registers upon wakeup.

If the transition into low power mode fails, then the CPU_PM framework
invokes the PM notifier callback with CPU_PM_ENTER_FAILED to allow the
drivers to undo the state changes.

The GIC V3 driver ignores CPU_PM_ENTER_FAILED, which leaves the GIC in
disabled state.

Handle CPU_PM_ENTER_FAILED in the same way as CPU_PM_EXIT to restore normal
operation.

[ tglx: Massage change log, add Fixes tag ]

Fixes: 3708d52fc6bb ("irqchip: gic-v3: Implement CPU PM notifier")
Signed-off-by: Yogesh Lal <[e-mail]>
Signed-off-by: Thomas Gleixner <[e-mail]>
Acked-by: Marc Zyngier <[e-mail]>
Cc: [e-mail]
Link: https://lore.kernel.org/all/[e-mail]

drivers/irqchip/irq-gic-v3.c

···
 static int gic_cpu_pm_notifier(struct notifier_block *self,
 			       unsigned long cmd, void *v)
 {
-	if (cmd == CPU_PM_EXIT) {
+	if (cmd == CPU_PM_EXIT || cmd == CPU_PM_ENTER_FAILED) {
 		if (gic_dist_security_disabled())
 			gic_enable_redist(true);
 		gic_cpu_sys_reg_enable();