diff options
Diffstat (limited to 'include/linux/ptp_clock_kernel.h')
| -rw-r--r-- | include/linux/ptp_clock_kernel.h | 46 |
1 files changed, 46 insertions, 0 deletions
diff --git a/include/linux/ptp_clock_kernel.h b/include/linux/ptp_clock_kernel.h index ad4aaadc2f7a..f4781c5766d6 100644 --- a/include/linux/ptp_clock_kernel.h +++ b/include/linux/ptp_clock_kernel.h @@ -248,6 +248,52 @@ static inline long scaled_ppm_to_ppb(long ppm) return (long)ppb; } +/** + * diff_by_scaled_ppm - Calculate difference using scaled ppm + * @base: the base increment value to adjust + * @scaled_ppm: scaled parts per million to adjust by + * @diff: on return, the absolute value of calculated diff + * + * Calculate the difference to adjust the base increment using scaled parts + * per million. + * + * Use mul_u64_u64_div_u64 to perform the difference calculation in avoid + * possible overflow. + * + * Returns: true if scaled_ppm is negative, false otherwise + */ +static inline bool diff_by_scaled_ppm(u64 base, long scaled_ppm, u64 *diff) +{ + bool negative = false; + + if (scaled_ppm < 0) { + negative = true; + scaled_ppm = -scaled_ppm; + } + + *diff = mul_u64_u64_div_u64(base, (u64)scaled_ppm, 1000000ULL << 16); + + return negative; +} + +/** + * adjust_by_scaled_ppm - Adjust a base increment by scaled parts per million + * @base: the base increment value to adjust + * @scaled_ppm: scaled parts per million frequency adjustment + * + * Helper function which calculates a new increment value based on the + * requested scaled parts per million adjustment. + */ +static inline u64 adjust_by_scaled_ppm(u64 base, long scaled_ppm) +{ + u64 diff; + + if (diff_by_scaled_ppm(base, scaled_ppm, &diff)) + return base - diff; + + return base + diff; +} + #if IS_ENABLED(CONFIG_PTP_1588_CLOCK) /** |