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lib: utils/timer: Simplify MTIMER synchronization

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We simplify MTIMER synchronization as follows:

1) Detect MTIMER devices with unique (or non-shared) MTIME
   register at boot-time
2) Select first MTIMER device with no associated HART as our
   reference MTIMER device
3) Only synchronize MTIMER devices with unique (or non-shared)
   MTIME register using reference MTIMER device
4) Directly update the MTIME register at time of synchronization
   because MTIME is a read/write register.

Signed-off-by: Anup Patel <anup.patel@wdc.com>
Reviewed-by: Atish Patra <atish.patra@wdc.com>
This commit is contained in:
Anup Patel
2021-07-24 10:35:01 +05:30
committed by Anup Patel
parent b35f7826b0
commit 7aa6c9aa96
3 changed files with 83 additions and 33 deletions
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67
lib/utils/timer/aclint_mtimer.c
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@@ -57,7 +57,7 @@ static u64 mtimer_value(void)
u64 *time_val = (void *)mt->mtime_addr;
/* Read MTIMER Time Value */
return mt->time_rd(time_val) + mt->time_delta;
return mt->time_rd(time_val);
}
static void mtimer_event_stop(void)
@@ -77,7 +77,7 @@ static void mtimer_event_start(u64 next_event)
u64 *time_cmp = (void *)mt->mtimecmp_addr;
/* Program MTIMER Time Compare */
mt->time_wr(true, next_event - mt->time_delta,
mt->time_wr(true, next_event,
&time_cmp[target_hart - mt->first_hartid]);
}
@@ -88,36 +88,51 @@ static struct sbi_timer_device mtimer = {
.timer_event_stop = mtimer_event_stop
};
void aclint_mtimer_sync(struct aclint_mtimer_data *mt)
{
u64 v1, v2, mv, delta;
u64 *mt_time_val, *ref_time_val;
struct aclint_mtimer_data *reference;
/* Sync-up non-shared MTIME if reference is available */
if (mt->has_shared_mtime || !mt->time_delta_reference)
return;
reference = mt->time_delta_reference;
mt_time_val = (void *)mt->mtime_addr;
ref_time_val = (void *)reference->mtime_addr;
if (!atomic_raw_xchg_ulong(&mt->time_delta_computed, 1)) {
v1 = mt->time_rd(mt_time_val);
mv = reference->time_rd(ref_time_val);
v2 = mt->time_rd(mt_time_val);
delta = mv - ((v1 / 2) + (v2 / 2));
mt->time_wr(false, mt->time_rd(mt_time_val) + delta,
mt_time_val);
}
}
void aclint_mtimer_set_reference(struct aclint_mtimer_data *mt,
struct aclint_mtimer_data *ref)
{
if (!mt || !ref || mt == ref)
return;
mt->time_delta_reference = ref;
mt->time_delta_computed = 0;
}
int aclint_mtimer_warm_init(void)
{
u64 v1, v2, mv;
u64 *mt_time_cmp;
u32 target_hart = current_hartid();
struct aclint_mtimer_data *reference;
u64 *mt_time_val, *mt_time_cmp, *ref_time_val;
struct aclint_mtimer_data *mt = mtimer_hartid2data[target_hart];
if (!mt)
return SBI_ENODEV;
/*
* Compute delta if reference available
*
* We deliberately compute time_delta in warm init so that time_delta
* is computed on a HART which is going to use given MTIMER. We use
* atomic flag timer_delta_computed to ensure that only one HART does
* time_delta computation.
*/
if (mt->time_delta_reference) {
reference = mt->time_delta_reference;
mt_time_val = (void *)mt->mtime_addr;
ref_time_val = (void *)reference->mtime_addr;
if (!atomic_raw_xchg_ulong(&mt->time_delta_computed, 1)) {
v1 = mt->time_rd(mt_time_val);
mv = reference->time_rd(ref_time_val);
v2 = mt->time_rd(mt_time_val);
mt->time_delta = mv - ((v1 / 2) + (v2 / 2));
}
}
/* Sync-up MTIME register */
aclint_mtimer_sync(mt);
/* Clear Time Compare */
mt_time_cmp = (void *)mt->mtimecmp_addr;
@@ -173,9 +188,7 @@ int aclint_mtimer_cold_init(struct aclint_mtimer_data *mt,
return SBI_EINVAL;
/* Initialize private data */
mt->time_delta_reference = reference;
mt->time_delta_computed = 0;
mt->time_delta = 0;
aclint_mtimer_set_reference(mt, reference);
mt->time_rd = mtimer_time_rd32;
mt->time_wr = mtimer_time_wr32;