From c734e8660ffe89536f61004eb4ee1f665529e111 Mon Sep 17 00:00:00 2001 From: Sebastian Huber Date: Fri, 8 Jan 2021 11:59:40 +0100 Subject: cpucounter: Increase conversion accuracy The maximum frequency is UINT32_MAX. Converted to a uint64_t variable it can be shifted by 32. The addition does not overflow since bin_per_s - 1 is UINT32_MAX. --- cpukit/sapi/src/cpucounterconverter.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) (limited to 'cpukit/sapi/src') diff --git a/cpukit/sapi/src/cpucounterconverter.c b/cpukit/sapi/src/cpucounterconverter.c index 08a745dfc6..88403987d2 100644 --- a/cpukit/sapi/src/cpucounterconverter.c +++ b/cpukit/sapi/src/cpucounterconverter.c @@ -42,19 +42,20 @@ int64_t rtems_counter_ticks_to_sbintime( rtems_counter_ticks ticks ) rtems_counter_ticks rtems_counter_sbintime_to_ticks( int64_t sbt ) { - return (rtems_counter_ticks) (((uint64_t) sbt * from_sbt_scaler) >> 31); + return (rtems_counter_ticks) (((uint64_t) sbt * from_sbt_scaler) >> 32); } void rtems_counter_initialize_converter( uint32_t frequency ) { uint64_t ns_per_s = UINT64_C(1000000000); uint64_t bin_per_s = UINT64_C(1) << 32; + uint64_t bin_freq = (uint64_t) frequency << 32; to_ns_scaler = ((ns_per_s << 32) + frequency - 1) / frequency; - from_ns_scaler = ((UINT64_C(1) << 32) * frequency + ns_per_s - 1) / ns_per_s; + from_ns_scaler = (bin_freq + ns_per_s - 1) / ns_per_s; to_sbt_scaler = ((bin_per_s << 31) + frequency - 1) / frequency; - from_sbt_scaler = ((UINT64_C(1) << 31) * frequency + bin_per_s - 1) / bin_per_s; + from_sbt_scaler = (bin_freq + bin_per_s - 1) / bin_per_s; } static void rtems_counter_sysinit( void ) -- cgit v1.2.3