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SubjectRe: [PATCH v2 net-next 4/4] time64.h: consolidate uses of PSEC_PER_NSEC


On 6/28/22 15:52, Vladimir Oltean wrote:
> Time-sensitive networking code needs to work with PTP times expressed in
> nanoseconds, and with packet transmission times expressed in
> picoseconds, since those would be fractional at higher than gigabit
> speed when expressed in nanoseconds.
>
> Convert the existing uses in tc-taprio and the ocelot/felix DSA driver
> to a PSEC_PER_NSEC macro. This macro is placed in include/linux/time64.h
> as opposed to its relatives (PSEC_PER_SEC etc) from include/vdso/time64.h
> because the vDSO library does not (yet) need/use it.
>
> Cc: Andy Lutomirski <luto@kernel.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
> Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>

Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com> # for the vDSO parts

> ---
> v1->v2:
> - move PSEC_PER_NSEC to include/linux/time64.h
> - add missing include of linux/time.h
>
> drivers/net/dsa/ocelot/felix_vsc9959.c | 5 +++--
> include/linux/time64.h | 3 +++
> net/sched/sch_taprio.c | 5 +++--
> 3 files changed, 9 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/net/dsa/ocelot/felix_vsc9959.c b/drivers/net/dsa/ocelot/felix_vsc9959.c
> index 27d8b56cc21c..28bd4892c30a 100644
> --- a/drivers/net/dsa/ocelot/felix_vsc9959.c
> +++ b/drivers/net/dsa/ocelot/felix_vsc9959.c
> @@ -16,6 +16,7 @@
> #include <linux/iopoll.h>
> #include <linux/mdio.h>
> #include <linux/pci.h>
> +#include <linux/time.h>
> #include "felix.h"
>
> #define VSC9959_NUM_PORTS 6
> @@ -1235,7 +1236,7 @@ static void vsc9959_tas_guard_bands_update(struct ocelot *ocelot, int port)
> u32 max_sdu;
>
> if (min_gate_len[tc] == U64_MAX /* Gate always open */ ||
> - min_gate_len[tc] * 1000 > needed_bit_time_ps) {
> + min_gate_len[tc] * PSEC_PER_NSEC > needed_bit_time_ps) {
> /* Setting QMAXSDU_CFG to 0 disables oversized frame
> * dropping.
> */
> @@ -1249,7 +1250,7 @@ static void vsc9959_tas_guard_bands_update(struct ocelot *ocelot, int port)
> * frame, make sure to enable oversize frame dropping
> * for frames larger than the smallest that would fit.
> */
> - max_sdu = div_u64(min_gate_len[tc] * 1000,
> + max_sdu = div_u64(min_gate_len[tc] * PSEC_PER_NSEC,
> picos_per_byte);
> /* A TC gate may be completely closed, which is a
> * special case where all packets are oversized.
> diff --git a/include/linux/time64.h b/include/linux/time64.h
> index 81b9686a2079..2fb8232cff1d 100644
> --- a/include/linux/time64.h
> +++ b/include/linux/time64.h
> @@ -20,6 +20,9 @@ struct itimerspec64 {
> struct timespec64 it_value;
> };
>
> +/* Parameters used to convert the timespec values: */
> +#define PSEC_PER_NSEC 1000L
> +
> /* Located here for timespec[64]_valid_strict */
> #define TIME64_MAX ((s64)~((u64)1 << 63))
> #define TIME64_MIN (-TIME64_MAX - 1)
> diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c
> index b9c71a304d39..0b941dd63d26 100644
> --- a/net/sched/sch_taprio.c
> +++ b/net/sched/sch_taprio.c
> @@ -18,6 +18,7 @@
> #include <linux/module.h>
> #include <linux/spinlock.h>
> #include <linux/rcupdate.h>
> +#include <linux/time.h>
> #include <net/netlink.h>
> #include <net/pkt_sched.h>
> #include <net/pkt_cls.h>
> @@ -176,7 +177,7 @@ static ktime_t get_interval_end_time(struct sched_gate_list *sched,
>
> static int length_to_duration(struct taprio_sched *q, int len)
> {
> - return div_u64(len * atomic64_read(&q->picos_per_byte), 1000);
> + return div_u64(len * atomic64_read(&q->picos_per_byte), PSEC_PER_NSEC);
> }
>
> /* Returns the entry corresponding to next available interval. If
> @@ -551,7 +552,7 @@ static struct sk_buff *taprio_peek(struct Qdisc *sch)
> static void taprio_set_budget(struct taprio_sched *q, struct sched_entry *entry)
> {
> atomic_set(&entry->budget,
> - div64_u64((u64)entry->interval * 1000,
> + div64_u64((u64)entry->interval * PSEC_PER_NSEC,
> atomic64_read(&q->picos_per_byte)));
> }
>

--
Regards,
Vincenzo

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