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[PATCH] hw/ppc: fix decrementer with BookE timers


From: Clément Chigot
Subject: [PATCH] hw/ppc: fix decrementer with BookE timers
Date: Mon, 15 Jul 2024 10:46:39 +0200

The BookE decrementer stops at 0, meaning that it won't decremented
towards "negative" values.
However, the current logic is inverted: decr is updated solely when
the resulting value would be negative.

Signed-off-by: Clément Chigot <chigot@adacore.com>
Fixed: 8e0a5ac87800 ("hw/ppc: Avoid decrementer rounding errors")
---
 hw/ppc/ppc.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/hw/ppc/ppc.c b/hw/ppc/ppc.c
index e6fa5580c0..9fc85c7de0 100644
--- a/hw/ppc/ppc.c
+++ b/hw/ppc/ppc.c
@@ -729,7 +729,9 @@ static inline int64_t __cpu_ppc_load_decr(CPUPPCState *env, 
int64_t now,
     int64_t decr;
 
     n = ns_to_tb(tb_env->decr_freq, now);
-    if (next > n && tb_env->flags & PPC_TIMER_BOOKE) {
+
+    /* BookE timers stop when reaching 0.  */
+    if (next < n && tb_env->flags & PPC_TIMER_BOOKE) {
         decr = 0;
     } else {
         decr = next - n;
-- 
2.25.1




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