motorhead/qemu
1
0
Fork 0
mirror of https://github.com/Motorhead1991/qemu.git synced 2025-08-04 00:03:54 -06:00
Code Issues Projects Releases Packages Wiki Activity Actions

hw/timer/armv7m_systick: Rewrite to use ptimers

Browse source 
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 <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-id: 20201015151829.14656-3-peter.maydell@linaro.org
This commit is contained in:
Peter Maydell 2020-10-15 16:18:29 +01:00
parent 68d59c6d8d
commit 32bd322a01
2 changed files with 54 additions and 73 deletions
Download patch file Download diff file Expand all files Collapse all files

3
include/hw/timer/armv7m_systick.h
View file

@ -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;
};