1. 25 Sep, 2018 1 commit
  2. 28 Feb, 2018 1 commit
  3. 25 Jan, 2018 1 commit
    • Julius Werner's avatar
      delay_timer: Guarantee that delay time can never be undershot · e2aec918
      Julius Werner authored
      
      
      Delay functions like udelay() are often used to ensure that the
      necessary time passed to allow some asynchronous event to finish, such
      as the stabilization delay for a power rail. For these use cases it is
      not very problematic if the delay is slightly longer than requested,
      but it is critical that the delay must never be shorter.
      
      The current udelay() implementation contains two hazards that may cause
      the delay to be slightly shorter than intended: Firstly, the amount of
      ticks to wait is calculated with an integer division, which may cut off
      the last fraction of ticks needed. Secondly, the delay may be short by a
      fraction of a tick because we do not know whether the initial ("start")
      sample of the timer was near the start or near the end of the current
      tick. Thus, if the code intends to wait for one tick, it might read the
      timer value close to the end of the current tick and then read it again
      right after the start of the next tick, concluding that the duration of
      a full tick has passed when it in fact was just a fraction of it.
      
      This patch rounds up the division and always adds one extra tick to
      counteract both problems and ensure that delays will always be larger
      but never smaller than requested.
      
      Change-Id: Ic5fe5f858b5cdf3c0dbf3e488d4d5702d9569433
      Signed-off-by: default avatarJulius Werner <jwerner@chromium.org>
      e2aec918
  4. 23 Jun, 2017 1 commit
  5. 03 May, 2017 1 commit
  6. 20 May, 2016 1 commit
    • Antonio Nino Diaz's avatar
      Implement generic delay timer · 0bcedb22
      Antonio Nino Diaz authored
      Add delay timer implementation based on the system generic counter.
      This either uses the platform's implementation of
      `plat_get_syscnt_freq()` or explicit clock multiplier/divider values
      provided by the platform.
      
      The current implementation of udelay has been modified to avoid
      unnecessary calculations while waiting on the loop and to make it
      easier to check for overflows.
      
      Change-Id: I9062e1d506dc2f68367fd9289250b93444721732
      0bcedb22
  7. 17 Jun, 2015 1 commit
    • Ryan Harkin's avatar
      Add a simple delay timer driver API · 9055c7d1
      Ryan Harkin authored
      
      
      The API is simple. The BSP or specific timer driver creates an
      instance of timer_ops_t, fills in the timer specific data, then calls
      timer_init(). The timer specific data includes a function pointer
      to return the timer value and a clock multiplier/divider. The ratio
      of the multiplier and the divider is the clock frequency in MHz.
      
      After that, mdelay() or udelay() can be called to delay execution for
      the specified time (milliseconds or microseconds, respectively).
      
      Change-Id: Icf8a295e1d25874f789bf28b7412156329dc975c
      Co-authored-by: default avatarDan Handley <dan.handley@arm.com>
      9055c7d1