diff mbox series

[PULL,24/39] hw/timer/armv7m_systick: Update clock source before enabling timer

Message ID 20220208113948.3217356-25-peter.maydell@linaro.org
State Accepted
Commit 77cd997161cc853c758b68eebb52827d56bc020e
Headers show
Series [PULL,01/39] target/arm: Fix sve_zcr_len_for_el for VHE mode running | expand

Commit Message

Peter Maydell Feb. 8, 2022, 11:39 a.m. UTC 
From: Richard Petri <git@rpls.de>

Starting the SysTick timer and changing the clock source a the same time
will result in an error, if the previous clock period was zero. For exmaple,
on the mps2-tz platforms, no refclk is present. Right after reset, the
configured ptimer period is zero, and trying to enabling it will turn it off
right away. E.g., code running on the platform setting

    SysTick->CTRL  = SysTick_CTRL_CLKSOURCE_Msk | SysTick_CTRL_ENABLE_Msk;

should change the clock source and enable the timer on real hardware, but
resulted in an error in qemu.

Signed-off-by: Richard Petri <git@rpls.de>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 20220201192650.289584-1-git@rpls.de
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 hw/timer/armv7m_systick.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)
diff mbox series

Patch

diff --git a/hw/timer/armv7m_systick.c b/hw/timer/armv7m_systick.c
index 3bd951dd044..5dfe39afe36 100644
--- a/hw/timer/armv7m_systick.c
+++ b/hw/timer/armv7m_systick.c
@@ -149,6 +149,10 @@  static MemTxResult systick_write(void *opaque, hwaddr addr,
         s->control &= 0xfffffff8;
         s->control |= value & 7;
 
+        if ((oldval ^ value) & SYSTICK_CLKSOURCE) {
+            systick_set_period_from_clock(s);
+        }
+
         if ((oldval ^ value) & SYSTICK_ENABLE) {
             if (value & SYSTICK_ENABLE) {
                 ptimer_run(s->ptimer, 0);
@@ -156,10 +160,6 @@  static MemTxResult systick_write(void *opaque, hwaddr addr,
                 ptimer_stop(s->ptimer);
             }
         }
-
-        if ((oldval ^ value) & SYSTICK_CLKSOURCE) {
-            systick_set_period_from_clock(s);
-        }
         ptimer_transaction_commit(s->ptimer);
         break;
     }