From: kettenis <kettenis@openbsd.org>
Date: Sat, 14 Jan 2023 23:38:23 +0000 (+0000)
Subject: Change suspend idle loop from WFE to WFI.  This avoids spurious wakeups
X-Git-Url: http://artulab.com/gitweb/?a=commitdiff_plain;h=41d0860c4b39d7b39c40e6990d2ab188a89f54bd;p=openbsd

Change suspend idle loop from WFE to WFI.  This avoids spurious wakeups
while other CPUs are still active.  And prepares us for deeper sleep states
which require an interrupt for wakeup anyway.

ok patrick@
---

diff --git a/sys/arch/arm64/arm64/cpu.c b/sys/arch/arm64/arm64/cpu.c
index 7c8e4999faf..6e9df72d7be 100644
--- a/sys/arch/arm64/arm64/cpu.c
+++ b/sys/arch/arm64/arm64/cpu.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: cpu.c,v 1.78 2022/12/23 17:46:49 kettenis Exp $	*/
+/*	$OpenBSD: cpu.c,v 1.79 2023/01/14 23:38:23 kettenis Exp $	*/
 
 /*
  * Copyright (c) 2016 Dale Rahn <drahn@dalerahn.com>
@@ -1012,6 +1012,12 @@ cpu_boot_secondary(struct cpu_info *ci)
 	atomic_setbits_int(&ci->ci_flags, CPUF_GO);
 	__asm volatile("dsb sy; sev" ::: "memory");
 
+	/*
+	 * Send an interrupt as well to make sure the CPU wakes up
+	 * regardless of whether it is in a WFE or a WFI loop.
+	 */
+	arm_send_ipi(ci, ARM_IPI_NOP);
+
 	while ((ci->ci_flags & CPUF_RUNNING) == 0)
 		__asm volatile("wfe");
 }
@@ -1084,7 +1090,7 @@ cpu_halt(void)
 	    READ_SPECIALREG(cntv_ctl_el0) | CNTV_CTL_IMASK);
 
 	while ((ci->ci_flags & CPUF_GO) == 0) {
-		__asm volatile("wfe");
+		__asm volatile("wfi");
 		count++;
 	}