diff options
author | Jiaxun Yang <jiaxun.yang@flygoat.com> | 2023-05-21 12:35:50 +0200 |
---|---|---|
committer | Philippe Mathieu-Daudé <philmd@linaro.org> | 2023-07-10 21:53:03 +0200 |
commit | b263688d236bc07266ce393fdce8c9b6bfd9d8d8 (patch) | |
tree | 6633ab2068b74ed2bd72ef5019739a40eb730321 /target/mips/sysemu | |
parent | fcb237e64f9d026c03d635579c7b288d0008a6e5 (diff) |
target/mips: Rework cp0_timer with clock API
Previous implementation of MIPS cp0_timer computes a
cp0_count_ns based on input clock. However rounding
error of cp0_count_ns can affect precision of cp0_timer.
Using clock API and a divider for cp0_timer, so we can
use clock_ns_to_ticks/clock_ns_to_ticks to avoid rounding
issue.
Also workaround the situation that in such handler flow:
count = read_c0_count()
write_c0_compare(count)
If timer had not progressed when compare was written, the
interrupt would trigger again.
Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-Id: <20230521110037.90049-1-jiaxun.yang@flygoat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Diffstat (limited to 'target/mips/sysemu')
-rw-r--r-- | target/mips/sysemu/cp0_timer.c | 35 |
1 files changed, 19 insertions, 16 deletions
diff --git a/target/mips/sysemu/cp0_timer.c b/target/mips/sysemu/cp0_timer.c index 70de95d338..9d2bcb0dea 100644 --- a/target/mips/sysemu/cp0_timer.c +++ b/target/mips/sysemu/cp0_timer.c @@ -28,15 +28,26 @@ #include "internal.h" /* MIPS R4K timer */ +static uint32_t cpu_mips_get_count_val(CPUMIPSState *env) +{ + int64_t now_ns; + now_ns = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL); + return env->CP0_Count + + (uint32_t)clock_ns_to_ticks(env->count_clock, now_ns); +} + static void cpu_mips_timer_update(CPUMIPSState *env) { uint64_t now_ns, next_ns; uint32_t wait; now_ns = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL); - wait = env->CP0_Compare - env->CP0_Count - - (uint32_t)(now_ns / env->cp0_count_ns); - next_ns = now_ns + (uint64_t)wait * env->cp0_count_ns; + wait = env->CP0_Compare - cpu_mips_get_count_val(env); + /* Clamp interval to overflow if virtual time had not progressed */ + if (!wait) { + wait = UINT32_MAX; + } + next_ns = now_ns + clock_ticks_to_ns(env->count_clock, wait); timer_mod(env->timer, next_ns); } @@ -64,7 +75,7 @@ uint32_t cpu_mips_get_count(CPUMIPSState *env) cpu_mips_timer_expire(env); } - return env->CP0_Count + (uint32_t)(now_ns / env->cp0_count_ns); + return cpu_mips_get_count_val(env); } } @@ -79,9 +90,8 @@ void cpu_mips_store_count(CPUMIPSState *env, uint32_t count) env->CP0_Count = count; } else { /* Store new count register */ - env->CP0_Count = count - - (uint32_t)(qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) / - env->cp0_count_ns); + env->CP0_Count = count - (uint32_t)clock_ns_to_ticks(env->count_clock, + qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL)); /* Update timer timer */ cpu_mips_timer_update(env); } @@ -107,8 +117,8 @@ void cpu_mips_start_count(CPUMIPSState *env) void cpu_mips_stop_count(CPUMIPSState *env) { /* Store the current value */ - env->CP0_Count += (uint32_t)(qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) / - env->cp0_count_ns); + env->CP0_Count += (uint32_t)clock_ns_to_ticks(env->count_clock, + qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL)); } static void mips_timer_cb(void *opaque) @@ -121,14 +131,7 @@ static void mips_timer_cb(void *opaque) return; } - /* - * ??? This callback should occur when the counter is exactly equal to - * the comparator value. Offset the count by one to avoid immediately - * retriggering the callback before any virtual time has passed. - */ - env->CP0_Count++; cpu_mips_timer_expire(env); - env->CP0_Count--; } void cpu_mips_clock_init(MIPSCPU *cpu) |