From 50dbd5eccd8d9874f9949d29dc67f3034474f050 Mon Sep 17 00:00:00 2001
From: joevt <joevt@shaw.ca>
Date: Thu, 15 Sep 2022 20:54:22 -0700
Subject: [PATCH] Fix RTC not always updating

Fixed an issue where RTC was not being updated if only the upper 32 bits (seconds) was read.
Also simplified things by always updating the timestamp instead of only when the seconds changes.
---
 cpu/ppc/ppcopcodes.cpp | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/cpu/ppc/ppcopcodes.cpp b/cpu/ppc/ppcopcodes.cpp
index 563e16a..8faab0a 100644
--- a/cpu/ppc/ppcopcodes.cpp
+++ b/cpu/ppc/ppcopcodes.cpp
@@ -855,18 +855,20 @@ void dppc_interpreter::ppc_mtmsr() {
     }
 }
 
-static inline uint64_t calc_rtcl_value()
+static inline void calc_rtcl_value()
 {
-    uint64_t diff    = get_virt_time_ns() - rtc_timestamp;
+    uint64_t new_ts = get_virt_time_ns();
+    uint64_t diff    = new_ts - rtc_timestamp;
     uint64_t rtc_inc = diff * tbr_freq_hz / NS_PER_SEC;
     uint64_t rtc_l   = rtc_lo + (rtc_inc << 7);
     if (rtc_l >= ONE_BILLION_NS) { // check RTCL overflow
         rtc_hi += rtc_l / ONE_BILLION_NS;
         rtc_lo  = rtc_l % ONE_BILLION_NS;
-        rtc_timestamp = get_virt_time_ns();
-        rtc_l =  rtc_lo;
     }
-    return rtc_l & 0x3FFFFF80UL;
+    else {
+        rtc_lo = rtc_l;
+    }
+    rtc_timestamp = new_ts;
 }
 
 void dppc_interpreter::ppc_mfspr() {
@@ -880,9 +882,11 @@ void dppc_interpreter::ppc_mfspr() {
 
     switch (ref_spr) {
     case SPR::RTCL_U:
-        ppc_state.spr[SPR::RTCL_U] = calc_rtcl_value();
+        calc_rtcl_value();
+        ppc_state.spr[SPR::RTCL_U] = rtc_lo & 0x3FFFFF80UL;
         break;
     case SPR::RTCU_U:
+        calc_rtcl_value();
         ppc_state.spr[SPR::RTCU_U] = rtc_hi;
         break;
     }