From: Christopher Hall <[email protected]> The PMC Time-Aware GPIO (TGPIO) logic is driven by ART. Several support functions are required to translate ART to/from nanoseconds units which is required by the PHC clock interface. A function is also added to get the current value of ART/TSC using get_cycles() (RDTSC). This avoids multiple MMIO reads required to retrieve ART.
Note that rather than ART nanoseconds, TSC nanoseconds are used. These are related by TSC = ART * CPUID[15H].EBX/CPUID[15H].EAX + K. The value of K is the distinction between between the ART and TSC nanoseconds. The advantage of using TSC nanoseconds to represent the device clock because it can easily be calculated in user-space using only CPUID[15H]. The value of ART in general can't be since K isn't necessarily known to the application. Signed-off-by: Christopher Hall <[email protected]> Signed-off-by: Zqiang <[email protected]> --- arch/x86/include/asm/tsc.h | 6 ++ arch/x86/kernel/tsc.c | 116 ++++++++++++++++++++++++++++++++++++- 2 files changed, 120 insertions(+), 2 deletions(-) diff --git a/arch/x86/include/asm/tsc.h b/arch/x86/include/asm/tsc.h index 01a300a9700b..721caa09a14d 100644 --- a/arch/x86/include/asm/tsc.h +++ b/arch/x86/include/asm/tsc.h @@ -30,6 +30,12 @@ static inline cycles_t get_cycles(void) extern struct system_counterval_t convert_art_to_tsc(u64 art); extern struct system_counterval_t convert_art_ns_to_tsc(u64 art_ns); +extern struct timespec64 get_tsc_ns_now(struct system_counterval_t + *system_counter); +extern u64 convert_tsc_ns_to_art(struct timespec64 *tsc_ns); +extern u64 convert_tsc_ns_to_art_duration(struct timespec64 *tsc_ns); +extern struct timespec64 convert_art_to_tsc_ns(u64 art); +extern struct timespec64 convert_art_to_tsc_ns_duration(u64 art); extern void tsc_early_init(void); extern void tsc_init(void); diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c index 9eae730d8b44..c4b48323c4bf 100644 --- a/arch/x86/kernel/tsc.c +++ b/arch/x86/kernel/tsc.c @@ -1260,7 +1260,7 @@ int unsynchronized_tsc(void) /* * Convert ART to TSC given numerator/denominator found in detect_art() */ -struct system_counterval_t convert_art_to_tsc(u64 art) +static struct system_counterval_t _convert_art_to_tsc(u64 art, bool dur) { u64 tmp, res, rem; @@ -1270,13 +1270,125 @@ struct system_counterval_t convert_art_to_tsc(u64 art) tmp = rem * art_to_tsc_numerator; do_div(tmp, art_to_tsc_denominator); - res += tmp + art_to_tsc_offset; + res += tmp; + if (!dur) + res += art_to_tsc_offset; return (struct system_counterval_t) {.cs = art_related_clocksource, .cycles = res}; } + +struct system_counterval_t convert_art_to_tsc(u64 art) +{ + return _convert_art_to_tsc(art, false); +} EXPORT_SYMBOL(convert_art_to_tsc); +static +struct timespec64 get_tsc_ns(struct system_counterval_t *system_counter) +{ + u64 tmp, res, rem; + u64 cycles; + + cycles = system_counter->cycles; + rem = do_div(cycles, tsc_khz); + + res = cycles * USEC_PER_SEC; + tmp = rem * USEC_PER_SEC; + + rem = do_div(tmp, tsc_khz); + tmp += rem > tsc_khz >> 2 ? 1 : 0; + res += tmp; + + rem = do_div(res, NSEC_PER_SEC); + + return (struct timespec64) {.tv_sec = res, .tv_nsec = rem}; +} + +struct timespec64 get_tsc_ns_now(struct system_counterval_t *system_counter) +{ + struct system_counterval_t counterval; + + if (system_counter == NULL) + system_counter = &counterval; + + system_counter->cycles = clocksource_tsc.read(NULL); + system_counter->cs = art_related_clocksource; + + return get_tsc_ns(system_counter); +} +EXPORT_SYMBOL(get_tsc_ns_now); + +struct timespec64 convert_art_to_tsc_ns(u64 art) +{ + struct system_counterval_t counterval; + + counterval = _convert_art_to_tsc(art, false); + + return get_tsc_ns(&counterval); +} +EXPORT_SYMBOL(convert_art_to_tsc_ns); + +struct timespec64 convert_art_to_tsc_ns_duration(u64 art) +{ + struct system_counterval_t counterval; + + counterval = _convert_art_to_tsc(art, true); + + return get_tsc_ns(&counterval); +} +EXPORT_SYMBOL(convert_art_to_tsc_ns_duration); + +static u64 convert_tsc_ns_to_tsc(struct timespec64 *tsc_ns) +{ + u64 tmp, res, rem; + u64 cycles; + + cycles = timespec64_to_ns(tsc_ns); + + rem = do_div(cycles, USEC_PER_SEC); + + res = cycles * tsc_khz; + tmp = rem * tsc_khz; + + do_div(tmp, USEC_PER_SEC); + + return res + tmp; +} + + +static u64 _convert_tsc_ns_to_art(struct timespec64 *tsc_ns, bool dur) +{ + u64 tmp, res, rem; + u64 cycles; + + cycles = convert_tsc_ns_to_tsc(tsc_ns); + if (!dur) + cycles -= art_to_tsc_offset; + + rem = do_div(cycles, art_to_tsc_numerator); + + res = cycles * art_to_tsc_denominator; + tmp = rem * art_to_tsc_denominator; + + rem = do_div(tmp, art_to_tsc_numerator); + tmp += rem > art_to_tsc_numerator >> 2 ? 1 : 0; + + return res + tmp; +} + +u64 convert_tsc_ns_to_art(struct timespec64 *tsc_ns) +{ + return _convert_tsc_ns_to_art(tsc_ns, false); +} +EXPORT_SYMBOL(convert_tsc_ns_to_art); + +u64 convert_tsc_ns_to_art_duration(struct timespec64 *tsc_ns) +{ + return _convert_tsc_ns_to_art(tsc_ns, true); +} +EXPORT_SYMBOL(convert_tsc_ns_to_art_duration); + /** * convert_art_ns_to_tsc() - Convert ART in nanoseconds to TSC. * @art_ns: ART (Always Running Timer) in unit of nanoseconds -- 2.25.1
