From 7cffd29be8ddc926f78306a722ae0466ca092588 Mon Sep 17 00:00:00 2001
From: Scott Soule Cheloha <cheloha@cvs.openbsd.org>
Date: Thu, 22 Dec 2022 19:51:12 +0000
Subject: sparc64: move retry logic out of stickcmpr_set()

In some cases, stickcmpr_set() fails to ensure that %STICK_CMPR leads
%STICK before returning to the caller.  Rewriting the retry logic in C
trivially fixes the issue.  So move the retry logic out into a new
function, stick_rearm().

Issue discovered by miod@, fix tested by miod@.

Link: https://marc.info/?l=openbsd-tech&m=167122933414238&w=2

ok kettenis@
---
 sys/arch/sparc64/sparc64/clock.c  | 25 +++++++++++++++++++++----
 sys/arch/sparc64/sparc64/locore.s | 18 +-----------------
 2 files changed, 22 insertions(+), 21 deletions(-)

(limited to 'sys/arch/sparc64')

diff --git a/sys/arch/sparc64/sparc64/clock.c b/sys/arch/sparc64/sparc64/clock.c
index 92c06d76ec6..56e1cb05a61 100644
--- a/sys/arch/sparc64/sparc64/clock.c
+++ b/sys/arch/sparc64/sparc64/clock.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: clock.c,v 1.72 2022/11/10 07:08:01 jmatthew Exp $	*/
+/*	$OpenBSD: clock.c,v 1.73 2022/12/22 19:51:11 cheloha Exp $	*/
 /*	$NetBSD: clock.c,v 1.41 2001/07/24 19:29:25 eeh Exp $ */
 
 /*
@@ -150,6 +150,8 @@ void	tick_start(void);
 void	sys_tick_start(void);
 void	stick_start(void);
 
+void	stick_rearm(uint64_t);
+
 int	tickintr(void *);
 int	sys_tickintr(void *);
 int	stickintr(void *);
@@ -810,7 +812,7 @@ stickintr(void *cap)
 
 	/* Reset the interrupt. */
 	s = intr_disable();
-	stickcmpr_set(ci->ci_tick);
+	stick_rearm(ci->ci_tick);
 	intr_restore(s);
 
 	return (1);
@@ -920,11 +922,26 @@ stick_start(void)
 	 */
 
 	s = intr_disable();
-	ci->ci_tick = roundup(stick(), tick_increment);
-	stickcmpr_set(ci->ci_tick);
+	ci->ci_tick = stick();
+	stick_rearm(ci->ci_tick);
 	intr_restore(s);
 }
 
+void
+stick_rearm(uint64_t cmp)
+{
+	uint64_t now, off = 8;
+
+	stickcmpr_set(cmp);
+	now = stick();
+	while (cmp <= now) {
+		cmp += off;
+		stickcmpr_set(cmp);
+		now = stick();
+		off *= 2;
+	}
+}
+
 u_int
 tick_get_timecount(struct timecounter *tc)
 {
diff --git a/sys/arch/sparc64/sparc64/locore.s b/sys/arch/sparc64/sparc64/locore.s
index 3025baf42d1..aa2e2065ade 100644
--- a/sys/arch/sparc64/sparc64/locore.s
+++ b/sys/arch/sparc64/sparc64/locore.s
@@ -1,4 +1,4 @@
-/*	$OpenBSD: locore.s,v 1.194 2022/12/08 01:25:45 guenther Exp $	*/
+/*	$OpenBSD: locore.s,v 1.195 2022/12/22 19:51:11 cheloha Exp $	*/
 /*	$NetBSD: locore.s,v 1.137 2001/08/13 06:10:10 jdolecek Exp $	*/
 
 /*
@@ -7568,26 +7568,10 @@ END(stick)
 
 ENTRY(stickcmpr_set)
 	setx	STICK_CMP_HIGH, %o1, %o3
-	mov	8, %o2			! Initial step size
-1:
 	srlx	%o0, 32, %o1
 	stxa	%o1, [%o3] ASI_PHYS_NON_CACHED
 	add	%o3, (STICK_CMP_LOW - STICK_CMP_HIGH), %o4
 	stxa	%o0, [%o4] ASI_PHYS_NON_CACHED
-
-	add	%o3, (STICK_REG_LOW - STICK_CMP_HIGH), %o4
-	ldxa	[%o4] ASI_PHYS_NON_CACHED, %o1
-	add	%o3, (STICK_REG_HIGH - STICK_CMP_HIGH), %o4
-	ldxa	[%o4] ASI_PHYS_NON_CACHED, %o5
-	sllx	%o5, 32, %o5
-	or	%o1, %o5, %o1
-
-	cmp	%o0, %o1		! Make sure the value we wrote
-	bg,pt	%xcc, 2f		!   was in the future
-	 add	%o0, %o2, %o0		! If not, add the step size, double
-	ba,pt	%xcc, 1b		!   the step size and try again.
-	 sllx	%o2, 1, %o2
-2:
 	retl
 	 nop
 END(stickcmpr_set)
-- 
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