diff options
Diffstat (limited to 'drivers/net/dsa/sja1105/sja1105_ptp.h')
| -rw-r--r-- | drivers/net/dsa/sja1105/sja1105_ptp.h | 27 |
1 files changed, 27 insertions, 0 deletions
diff --git a/drivers/net/dsa/sja1105/sja1105_ptp.h b/drivers/net/dsa/sja1105/sja1105_ptp.h index 6f4a19eec709..119e345b40fc 100644 --- a/drivers/net/dsa/sja1105/sja1105_ptp.h +++ b/drivers/net/dsa/sja1105/sja1105_ptp.h @@ -21,6 +21,33 @@ static inline s64 sja1105_ticks_to_ns(s64 ticks) return ticks * SJA1105_TICK_NS; } +/* Calculate the first base_time in the future that satisfies this + * relationship: + * + * future_base_time = base_time + N x cycle_time >= now, or + * + * now - base_time + * N >= --------------- + * cycle_time + * + * Because N is an integer, the ceiling value of the above "a / b" ratio + * is in fact precisely the floor value of "(a + b - 1) / b", which is + * easier to calculate only having integer division tools. + */ +static inline s64 future_base_time(s64 base_time, s64 cycle_time, s64 now) +{ + s64 a, b, n; + + if (base_time >= now) + return base_time; + + a = now - base_time; + b = cycle_time; + n = div_s64(a + b - 1, b); + + return base_time + n * cycle_time; +} + struct sja1105_ptp_cmd { u64 ptpstrtsch; /* start schedule */ u64 ptpstopsch; /* stop schedule */ |