[PATCH v2 5/5] lib: utils/timer: Simplify MTIMER synchronization
Atish Patra
atishp at atishpatra.org
Wed Aug 11 14:07:30 PDT 2021
On Sat, Aug 7, 2021 at 6:34 AM Anup Patel <anup.patel at wdc.com> wrote:
>
> 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 at wdc.com>
> ---
> include/sbi_utils/timer/aclint_mtimer.h | 7 ++-
> lib/utils/timer/aclint_mtimer.c | 67 +++++++++++++++----------
> lib/utils/timer/fdt_timer_mtimer.c | 39 ++++++++++++--
> 3 files changed, 80 insertions(+), 33 deletions(-)
>
> diff --git a/include/sbi_utils/timer/aclint_mtimer.h b/include/sbi_utils/timer/aclint_mtimer.h
> index fdc46cd..a9fe445 100644
> --- a/include/sbi_utils/timer/aclint_mtimer.h
> +++ b/include/sbi_utils/timer/aclint_mtimer.h
> @@ -31,14 +31,19 @@ struct aclint_mtimer_data {
> u32 first_hartid;
> u32 hart_count;
> bool has_64bit_mmio;
> + bool has_shared_mtime;
> /* Private details (initialized and used by ACLINT MTIMER library) */
> struct aclint_mtimer_data *time_delta_reference;
> unsigned long time_delta_computed;
> - u64 time_delta;
> u64 (*time_rd)(volatile u64 *addr);
> void (*time_wr)(bool timecmp, u64 value, volatile u64 *addr);
> };
>
> +void aclint_mtimer_sync(struct aclint_mtimer_data *mt);
> +
> +void aclint_mtimer_set_reference(struct aclint_mtimer_data *mt,
> + struct aclint_mtimer_data *ref);
> +
> int aclint_mtimer_warm_init(void);
>
> int aclint_mtimer_cold_init(struct aclint_mtimer_data *mt,
> diff --git a/lib/utils/timer/aclint_mtimer.c b/lib/utils/timer/aclint_mtimer.c
> index 0e4e846..d612b12 100644
> --- a/lib/utils/timer/aclint_mtimer.c
> +++ b/lib/utils/timer/aclint_mtimer.c
> @@ -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;
>
> diff --git a/lib/utils/timer/fdt_timer_mtimer.c b/lib/utils/timer/fdt_timer_mtimer.c
> index 15a36ed..26b5a2a 100644
> --- a/lib/utils/timer/fdt_timer_mtimer.c
> +++ b/lib/utils/timer/fdt_timer_mtimer.c
> @@ -17,19 +17,18 @@
>
> static unsigned long mtimer_count = 0;
> static struct aclint_mtimer_data mtimer[MTIMER_MAX_NR];
> +static struct aclint_mtimer_data *mt_reference = NULL;
>
> static int timer_mtimer_cold_init(void *fdt, int nodeoff,
> const struct fdt_match *match)
> {
> - int rc;
> + int i, rc;
> unsigned long offset, addr[2], size[2];
> - struct aclint_mtimer_data *mt, *mtmaster = NULL;
> + struct aclint_mtimer_data *mt;
>
> if (MTIMER_MAX_NR <= mtimer_count)
> return SBI_ENOSPC;
> mt = &mtimer[mtimer_count];
> - if (0 < mtimer_count)
> - mtmaster = &mtimer[0];
>
> rc = fdt_parse_aclint_node(fdt, nodeoff, true,
> &addr[0], &size[0], &addr[1], &size[1],
> @@ -37,6 +36,7 @@ static int timer_mtimer_cold_init(void *fdt, int nodeoff,
> if (rc)
> return rc;
> mt->has_64bit_mmio = true;
> + mt->has_shared_mtime = false;
>
> if (match->data) { /* SiFive CLINT */
> /* Set CLINT addresses */
> @@ -63,10 +63,39 @@ static int timer_mtimer_cold_init(void *fdt, int nodeoff,
> mt->has_64bit_mmio = false;
> }
>
> - rc = aclint_mtimer_cold_init(mt, mtmaster);
> + /* Check if MTIMER device has shared MTIME address */
> + mt->has_shared_mtime = false;
> + for (i = 0; i < mtimer_count; i++) {
> + if (mtimer[i].mtime_addr == mt->mtime_addr) {
> + mt->has_shared_mtime = true;
> + break;
> + }
> + }
> +
> + /* Initialize the MTIMER device */
> + rc = aclint_mtimer_cold_init(mt, mt_reference);
> if (rc)
> return rc;
>
> + /*
> + * Select first MTIMER device with no associated HARTs as
> + * our reference MTIMER device
> + */
> + if (!mt->hart_count && !mt_reference) {
> + mt_reference = mt;
> + /*
> + * Set reference for already propbed MTIMER devices
> + * with non-shared MTIME
> + */
> + for (i = 0; i < mtimer_count; i++)
> + if (!mtimer[i].has_shared_mtime)
> + aclint_mtimer_set_reference(&mtimer[i], mt);
> + }
> +
Is there a reason this is done after cold_init ?
> + /* Explicitly sync-up MTIMER devices not associated with any HARTs */
> + if (!mt->hart_count)
> + aclint_mtimer_sync(mt);
> +
> mtimer_count++;
> return 0;
> }
> --
> 2.25.1
>
>
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--
Regards,
Atish
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