Add a function to put a co-processor into the lowest possible power
state from which recovery usually isn't possible without a full SoC
reset. This is required for the USB4/Thunderbolt co-processors which
can be restarted since the entire USB4 root complex can be completely
reset independently of the rest of the SoC.

Signed-off-by: Sven Peter <sven@kernel.org>
---
 drivers/soc/apple/rtkit.c       | 17 +++++++++++++++++
 include/linux/soc/apple/rtkit.h |  7 +++++++
 2 files changed, 24 insertions(+)

diff --git a/drivers/soc/apple/rtkit.c b/drivers/soc/apple/rtkit.c
index b8d4da147d23f7e99e76eea314e4d976cddbd1c6..381faaf74d5982163d2c44d1e2c6e0ddad07bd73 100644
--- a/drivers/soc/apple/rtkit.c
+++ b/drivers/soc/apple/rtkit.c

@@ -851,6 +851,23 @@ int apple_rtkit_shutdown(struct apple_rtkit *rtk)
 }
 EXPORT_SYMBOL_GPL(apple_rtkit_shutdown);
 
+int apple_rtkit_poweroff(struct apple_rtkit *rtk)
+{
+	int ret;
+
+	ret = apple_rtkit_set_ap_power_state(rtk,
+					     APPLE_RTKIT_PWR_STATE_OFF);
+	if (ret)
+		return ret;
+
+	ret = apple_rtkit_set_iop_power_state(rtk, APPLE_RTKIT_PWR_STATE_OFF);

+	if (ret)
+		return ret;
+
+	return apple_rtkit_reinit(rtk);
+}
+EXPORT_SYMBOL_GPL(apple_rtkit_poweroff);
+
 int apple_rtkit_idle(struct apple_rtkit *rtk)
 {
 	int ret;

diff --git a/include/linux/soc/apple/rtkit.h b/include/linux/soc/apple/rtkit.h
index 736f530180179bd144cf85eb0f0bd93844d7188a..bda3c528b51553c13f7fe5685ab60f7fc675361b 100644
--- a/include/linux/soc/apple/rtkit.h
+++ b/include/linux/soc/apple/rtkit.h

@@ -125,6 +125,13 @@ int apple_rtkit_wake(struct apple_rtkit *rtk);
  */
 int apple_rtkit_shutdown(struct apple_rtkit *rtk);
 
+/*
+ * Put the co-processor into the lowest power state. Note that it usually
+ * is not possible to recover from this state without a full SoC reset.
+ */
+
+int apple_rtkit_poweroff(struct apple_rtkit *rtk);
+
 /*
  * Put the co-processor into idle mode
  */