From f5a9669a21e61ac3a60d70b5e1ba244021949b7d Mon Sep 17 00:00:00 2001
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Thu, 26 Jul 2018 15:03:16 +0200
Subject: [PATCH 417/518] efi: Disable runtime services on RT

[ Upstream commit 55544e1d5eb0d7608e2b41452729649c8ea1607a ]

Based on meassurements the EFI functions get_variable /
get_next_variable take up to 2us which looks okay.
The functions get_time, set_time take around 10ms. Those 10ms are too
much. Even one ms would be too much.
Ard mentioned that SetVariable might even trigger larger latencies if
the firware will erase flash blocks on NOR.

The time-functions are used by efi-rtc and can be triggered during
runtimed (either via explicit read/write or ntp sync).

The variable write could be used by pstore.
These functions can be disabled without much of a loss. The poweroff /
reboot hooks may be provided by PSCI.

Disable EFI's runtime wrappers.

This was observed on "EFI v2.60 by SoftIron Overdrive 1000".

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 drivers/firmware/efi/efi.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index 370bc0174f790..c5c3f0be64c08 100644
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -74,7 +74,7 @@ static unsigned long *efi_tables[] = {
 	&efi.mem_attr_table,
 };
 
-static bool disable_runtime;
+static bool disable_runtime = IS_ENABLED(CONFIG_PREEMPT_RT_BASE);
 static int __init setup_noefi(char *arg)
 {
 	disable_runtime = true;
-- 
2.41.0

