From 32bd322a0134ed89db00f2b9b3894982db3dedcb Mon Sep 17 00:00:00 2001 From: Peter Maydell Date: Thu, 15 Oct 2020 16:18:29 +0100 Subject: hw/timer/armv7m_systick: Rewrite to use ptimers MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The armv7m systick timer is a 24-bit decrementing, wrap-on-zero, clear-on-write counter. Our current implementation has various bugs and dubious workarounds in it (for instance see https://bugs.launchpad.net/qemu/+bug/1872237). We have an implementation of a simple decrementing counter and we put a lot of effort into making sure it handles the interesting corner cases (like "spend a cycle at 0 before reloading") -- ptimer. Rewrite the systick timer to use a ptimer rather than a raw QEMU timer. Unfortunately this is a migration compatibility break, which will affect all M-profile boards. Among other bugs, this fixes https://bugs.launchpad.net/qemu/+bug/1872237 : now writes to SYST_CVR when the timer is enabled correctly do nothing; when the timer is enabled via SYST_CSR.ENABLE, the ptimer code will (because of POLICY_NO_IMMEDIATE_RELOAD) arrange that after one timer tick the counter is reloaded from SYST_RVR and then counts down from there, as the architecture requires. Signed-off-by: Peter Maydell Reviewed-by: Philippe Mathieu-Daudé Message-id: 20201015151829.14656-3-peter.maydell@linaro.org --- include/hw/timer/armv7m_systick.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'include/hw/timer/armv7m_systick.h') diff --git a/include/hw/timer/armv7m_systick.h b/include/hw/timer/armv7m_systick.h index 97cb345ddb..84496faaf9 100644 --- a/include/hw/timer/armv7m_systick.h +++ b/include/hw/timer/armv7m_systick.h @@ -14,6 +14,7 @@ #include "hw/sysbus.h" #include "qom/object.h" +#include "hw/ptimer.h" #define TYPE_SYSTICK "armv7m_systick" @@ -27,7 +28,7 @@ struct SysTickState { uint32_t control; uint32_t reload; int64_t tick; - QEMUTimer *timer; + ptimer_state *ptimer; MemoryRegion iomem; qemu_irq irq; }; -- cgit v1.2.3