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Re: [PATCH] mos6522: update counters when timer interrupts are off


From: Philippe Mathieu-Daudé
Subject: Re: [PATCH] mos6522: update counters when timer interrupts are off
Date: Mon, 25 Nov 2019 15:37:52 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.1.1

On 11/25/19 3:14 PM, Laurent Vivier wrote:
Even if the interrupts are off, counters must be updated because
they are running anyway and kernel can try to read them
(it's the case with g3beige kernel).

Reported-by: Andrew Randrianasulu <address@hidden>
Signed-off-by: Laurent Vivier <address@hidden>
---
  hw/misc/mos6522.c | 8 ++++++--
  1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/hw/misc/mos6522.c b/hw/misc/mos6522.c
index aa3bfe1afd..cecf0be59e 100644
--- a/hw/misc/mos6522.c
+++ b/hw/misc/mos6522.c
@@ -113,6 +113,10 @@ static int64_t get_next_irq_time(MOS6522State *s, 
MOS6522Timer *ti,
      int64_t d, next_time;
      unsigned int counter;

Can you add a comment here such "Clock disabled. This is the longest time before expiration" or better?

Reviewed-by: Philippe Mathieu-Daudé <address@hidden>

+    if (ti->frequency == 0) {
+        return INT64_MAX;
+    }
+
      /* current counter value */
      d = muldiv64(qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) - ti->load_time,
                   ti->frequency, NANOSECONDS_PER_SECOND);
@@ -149,10 +153,10 @@ static void mos6522_timer1_update(MOS6522State *s, 
MOS6522Timer *ti,
      if (!ti->timer) {
          return;
      }
+    ti->next_irq_time = get_next_irq_time(s, ti, current_time);
      if ((s->ier & T1_INT) == 0 || (s->acr & T1MODE) != T1MODE_CONT) {
          timer_del(ti->timer);
      } else {
-        ti->next_irq_time = get_next_irq_time(s, ti, current_time);
          timer_mod(ti->timer, ti->next_irq_time);
      }
  }
@@ -163,10 +167,10 @@ static void mos6522_timer2_update(MOS6522State *s, 
MOS6522Timer *ti,
      if (!ti->timer) {
          return;
      }
+    ti->next_irq_time = get_next_irq_time(s, ti, current_time);
      if ((s->ier & T2_INT) == 0) {
          timer_del(ti->timer);
      } else {
-        ti->next_irq_time = get_next_irq_time(s, ti, current_time);
          timer_mod(ti->timer, ti->next_irq_time);
      }
  }





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