Changeset c734e86 in rtems

Timestamp:

Jan 8, 2021, 10:59:40 AM (3 months ago)

Author:

Sebastian Huber <sebastian.huber@…>

Branches:

master

Children:

30c71c3

Parents:

9d2db27a

git-author:

Sebastian Huber <sebastian.huber@…> (01/08/21 10:59:40)

git-committer:

Sebastian Huber <sebastian.huber@…> (01/26/21 14:29:36)

Message:

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.

File:

• cpukit/sapi/src/cpucounterconverter.c (modified) (2 diffs)

cpukit/sapi/src/cpucounterconverter.c

@@ -43 +43 @@
 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);
 }
 
@@ -50 +50 @@
   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;
 }