diff options
Diffstat (limited to 'include/linux/ptp_clock_kernel.h')
| -rw-r--r-- | include/linux/ptp_clock_kernel.h | 34 |
1 files changed, 26 insertions, 8 deletions
diff --git a/include/linux/ptp_clock_kernel.h b/include/linux/ptp_clock_kernel.h index 0d47fd33b228..a311bddd9e85 100644 --- a/include/linux/ptp_clock_kernel.h +++ b/include/linux/ptp_clock_kernel.h @@ -186,6 +186,32 @@ struct ptp_clock_event { }; }; +/** + * scaled_ppm_to_ppb() - convert scaled ppm to ppb + * + * @ppm: Parts per million, but with a 16 bit binary fractional field + */ +static inline s32 scaled_ppm_to_ppb(long ppm) +{ + /* + * The 'freq' field in the 'struct timex' is in parts per + * million, but with a 16 bit binary fractional field. + * + * We want to calculate + * + * ppb = scaled_ppm * 1000 / 2^16 + * + * which simplifies to + * + * ppb = scaled_ppm * 125 / 2^13 + */ + s64 ppb = 1 + ppm; + + ppb *= 125; + ppb >>= 13; + return (s32)ppb; +} + #if IS_REACHABLE(CONFIG_PTP_1588_CLOCK) /** @@ -230,14 +256,6 @@ extern void ptp_clock_event(struct ptp_clock *ptp, extern int ptp_clock_index(struct ptp_clock *ptp); /** - * scaled_ppm_to_ppb() - convert scaled ppm to ppb - * - * @ppm: Parts per million, but with a 16 bit binary fractional field - */ - -extern s32 scaled_ppm_to_ppb(long ppm); - -/** * ptp_find_pin() - obtain the pin index of a given auxiliary function * * The caller must hold ptp_clock::pincfg_mux. Drivers do not have |