[RTEMS Project] #4749: Clock Driver Validation

[RTEMS trac]

#4749: Clock Driver Validation
--------------------------+-------------------------------------
  Reporter:  Matt Joyce   |      Owner:  Sebastian Huber
      Type:  enhancement  |     Status:  assigned
  Priority:  normal       |  Milestone:
 Component:  test         |    Version:  6
  Severity:  normal       |   Keywords:  clock driver, testsuite
Blocked By:               |   Blocking:
--------------------------+-------------------------------------
 The current testsuite requires additional work to properly validate clock
 drivers. See, for example, this off-by-one bug patch, sent by a user on 26
 Oct 2022:

 --- a/bsps/arm/shared/clock/clock-armv7m.c
 +++ b/bsps/arm/shared/clock/clock-armv7m.c
 @@ -90,7 +90,7 @@ static void _ARMV7M_Clock_initialize_early(void)

 interval = (uint32_t) ((freq * us_per_tick) / 1000000);
 -systick->rvr = interval;
 +systick->rvr = interval - 1;
 systick->cvr = 0;
 systick->csr = ARMV7M_SYSTICK_CSR_ENABLE | ARMV7M_SYSTICK_CSR_CLKSOURCE;
 }

 Currently, the tests do not use an external clock source to verify the
 internal one. We propose to address this by adding tests using the Pulse-
 Per-Second (PPS) functionality from a GPS signal to validate the clock
 drivers over a set time interval. This will help to catch not only errors
 such as the one above, but also potential bugs related to time interval
 jitter.

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Ticket URL: <http://devel.rtems.org/ticket/4749>
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