From bbd72a8c7907533c6a559b209eb822187eb19448 Mon Sep 17 00:00:00 2001
From: kettenis <kettenis@openbsd.org>
Date: Sun, 5 Feb 2023 13:37:51 +0000
Subject: [PATCH] Implement usertc corresponding to the Allwinner A64
 agtimer(4) errata.

ok cheloha@, semarie@
---
 lib/libc/arch/aarch64/gen/usertc.c | 32 +++++++++++++++++++++++++++---
 1 file changed, 29 insertions(+), 3 deletions(-)

diff --git a/lib/libc/arch/aarch64/gen/usertc.c b/lib/libc/arch/aarch64/gen/usertc.c
index d1dd51c9a78..b7efb79aa3c 100644
--- a/lib/libc/arch/aarch64/gen/usertc.c
+++ b/lib/libc/arch/aarch64/gen/usertc.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: usertc.c,v 1.2 2020/07/15 22:58:33 kettenis Exp $	*/
+/*	$OpenBSD: usertc.c,v 1.3 2023/02/05 13:37:51 kettenis Exp $	*/
 /*
  * Copyright (c) 2020 Mark Kettenis <kettenis@openbsd.org>
  *
@@ -18,8 +18,25 @@
 #include <sys/types.h>
 #include <sys/timetc.h>
 
+static inline uint64_t
+agtimer_readcnt64_sun50i(void)
+{
+	uint64_t val;
+	int retry;
+
+	__asm volatile("isb" ::: "memory");
+	for (retry = 0; retry < 150; retry++) {
+		__asm volatile("mrs %x0, CNTVCT_EL0" : "=r" (val));
+
+		if (((val + 1) & 0x1ff) > 1)
+			break;
+	}
+
+	return val;
+}
+
 static inline u_int
-agtimer_get_timecount(struct timecounter *tc)
+agtimer_get_timecount_default(struct timecounter *tc)
 {
 	uint64_t val;
 
@@ -32,12 +49,21 @@ agtimer_get_timecount(struct timecounter *tc)
 	return (val & 0xffffffff);
 }
 
+static inline u_int
+agtimer_get_timecount_sun50i(struct timecounter *tc)
+{
+	return agtimer_readcnt64_sun50i();
+}
+
 static int
 tc_get_timecount(struct timekeep *tk, u_int *tc)
 {
 	switch (tk->tk_user) {
 	case TC_AGTIMER:
-		*tc = agtimer_get_timecount(NULL);
+		*tc = agtimer_get_timecount_default(NULL);
+		return 0;
+	case TC_AGTIMER_SUN50I:
+		*tc = agtimer_get_timecount_sun50i(NULL);
 		return 0;
 	}
 
-- 
2.20.1