um: Allow PM with suspend-to-idle

In order to be able to experiment with suspend in UML, add the
minimal work to be able to suspend (s2idle) an instance of UML,
and be able to wake it back up from that state with the USR1
signal sent to the main UML process.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Acked-By: Anton Ivanov <anton.ivanov@cambridgegreys.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

1 files changed, 25 insertions, 0 deletions

diff --git a/arch/um/kernel/um_arch.c b/arch/um/kernel/um_arch.c
index 76b37297b7d4..237a8d73a096 100644
--- a/arch/um/kernel/um_arch.c
+++ b/arch/um/kernel/um_arch.c
@@ -13,6 +13,7 @@
 #include <linux/sched.h>
 #include <linux/sched/task.h>
 #include <linux/kmsg_dump.h>
+#include <linux/suspend.h>
 
 #include <asm/processor.h>
 #include <asm/sections.h>
@@ -377,3 +378,27 @@ void *text_poke(void *addr, const void *opcode, size_t len)
 void text_poke_sync(void)
 {
 }
+
+#ifdef CONFIG_PM_SLEEP
+void uml_pm_wake(void)
+{
+	pm_system_wakeup();
+}
+
+static int init_pm_wake_signal(void)
+{
+	/*
+	 * In external time-travel mode we can't use signals to wake up
+	 * since that would mess with the scheduling. We'll have to do
+	 * some additional work to support wakeup on virtio devices or
+	 * similar, perhaps implementing a fake RTC controller that can
+	 * trigger wakeup (and request the appropriate scheduling from
+	 * the external scheduler when going to suspend.)
+	 */
+	if (time_travel_mode != TT_MODE_EXTERNAL)
+		register_pm_wake_signal();
+	return 0;
+}
+
+late_initcall(init_pm_wake_signal);
+#endif