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hw/intc: riscv_aclint: Fix mtime write for sstc extension

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When changing the mtime value, the period of [s|vs]timecmp timers
should also be updated, similar to the period of mtimecmp timer.

The period of the stimecmp timer is the time until the next S-mode
timer IRQ. The value is calculated as "stimecmp - time". [1]
It is equal to "stimecmp - mtime" since the time CSR is a read-only
shadow of the memory-mapped mtime register.
Thus, changing mtime value will update the period of stimecmp timer.

Similarly, the period of vstimecmp timer is calculated as "vstimecmp -
(mtime + htimedelta)" [2], so changing mtime value will update the
period of vstimecmp timer.

[1] RISC-V Priv spec ch 9.1.1. Supervisor Timer (stimecmp) Register
A supervisor timer interrupt becomes pending, as reflected in the STIP
bit in the mip and sip registers whenever time contains a value
greater than or equal to stimecmp.
[2] RISC-V Priv spec ch19.2.1. Virtual Supervisor Timer (vstimecmp) Register
A virtual supervisor timer interrupt becomes pending, as reflected in
the VSTIP bit in the hip register, whenever (time + htimedelta),
truncated to 64 bits, contains a value greater than or equal to
vstimecmp

Signed-off-by: Jim Shu <jim.shu@sifive.com>
Acked-by: Alistair Francis <alistair.francis@wdc.com>
Message-ID: <20250519143518.11086-3-jim.shu@sifive.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
This commit is contained in:
Jim Shu 2025-05-19 22:35:16 +08:00 • committed by Alistair Francis
parent 6eba6fe967
commit af27fc569a
1 changed files with 5 additions and 0 deletions
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5
hw/intc/riscv_aclint.c
View file

@ -28,6 +28,7 @@
#include "qemu/module.h"
#include "hw/sysbus.h"
#include "target/riscv/cpu.h"
#include "target/riscv/time_helper.h"
#include "hw/qdev-properties.h"
#include "hw/intc/riscv_aclint.h"
#include "qemu/timer.h"
@ -240,6 +241,10 @@ static void riscv_aclint_mtimer_write(void *opaque, hwaddr addr,
riscv_aclint_mtimer_write_timecmp(mtimer, RISCV_CPU(cpu),
mtimer->hartid_base + i,
mtimer->timecmp[i]);
riscv_timer_write_timecmp(env, env->stimer, env->stimecmp, 0, MIP_STIP);
riscv_timer_write_timecmp(env, env->vstimer, env->vstimecmp,
env->htimedelta, MIP_VSTIP);
}
return;
}