ACPI: s2idle: Log when enabling wakeup IRQ fails

enable_irq_wake() can fail. Previously acpi_s2idle_prepare() silently
ignored it's return code. Based on [1] we should try to continue even in
case of an error, so just log a warning for now.

Discovered when trying to go into s2idle under Xen. This leads to a
system that can't be woken, since xen-pirq currently doesn't support
setting wakeup IRQs [2]. With this you get at least some helpful log
message if you have access to console messages.

Link: https://lore.kernel.org/linux-acpi/20230313125344.2893-1-simon@invisiblethingslab.com/ # v1
Link: https://lore.kernel.org/linux-acpi/CAJZ5v0jahjt58nP6P5+xRdtD_ndYPvq4ecMVz6nfGu9tf5iaUw@mail.gmail.com/ # [1]
Link: https://lore.kernel.org/xen-devel/20230313134102.3157-1-simon@invisiblethingslab.com/ # [2]
Signed-off-by: Simon Gaiser <simon@invisiblethingslab.com>
[ rjw: Adjust white space ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/sleep.c

@@ -714,7 +714,13 @@ int acpi_s2idle_begin(void)
 int acpi_s2idle_prepare(void)
 {
 	if (acpi_sci_irq_valid()) {
-		enable_irq_wake(acpi_sci_irq);
+		int error;
+
+		error = enable_irq_wake(acpi_sci_irq);
+		if (error)
+			pr_warn("Warning: Failed to enable wakeup from IRQ %d: %d\n",
+				acpi_sci_irq, error);
+
 		acpi_ec_set_gpe_wake_mask(ACPI_GPE_ENABLE);
 	}