From 77cd997161cc853c758b68eebb52827d56bc020e Mon Sep 17 00:00:00 2001 From: Richard Petri Date: Tue, 1 Feb 2022 20:26:51 +0100 Subject: [PATCH] hw/timer/armv7m_systick: Update clock source before enabling timer 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 Reviewed-by: Peter Maydell Message-id: 20220201192650.289584-1-git@rpls.de Signed-off-by: Peter Maydell --- hw/timer/armv7m_systick.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/hw/timer/armv7m_systick.c b/hw/timer/armv7m_systick.c index 3bd951dd04..5dfe39afe3 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; } -- 2.11.4.GIT