1. 11 12月, 2014 3 次提交
  2. 09 12月, 2014 1 次提交
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  4. 05 12月, 2014 1 次提交
    • D
      clocksource: arch_timer: Allow the device tree to specify uninitialized timer registers · 65b5732d
      Doug Anderson 提交于
      Some 32-bit (ARMv7) systems are architected like this:
      
      * The firmware doesn't know and doesn't care about hypervisor mode and
        we don't want to add the complexity of hypervisor there.
      
      * The firmware isn't involved in SMP bringup or resume.
      
      * The ARCH timer come up with an uninitialized offset (CNTVOFF)
        between the virtual and physical counters.  Each core gets a
        different random offset.
      
      * The device boots in "Secure SVC" mode.
      
      * Nothing has touched the reset value of CNTHCTL.PL1PCEN or
        CNTHCTL.PL1PCTEN (both default to 1 at reset)
      
      On systems like the above, it doesn't make sense to use the virtual
      counter.  There's nobody managing the offset and each time a core goes
      down and comes back up it will get reinitialized to some other random
      value.
      
      This adds an optional property which can inform the kernel of this
      situation, and firmware is free to remove the property if it is going
      to initialize the CNTVOFF registers when each CPU comes out of reset.
      
      Currently, the best course of action in this case is to use the
      physical timer, which is why it is important that CNTHCTL hasn't been
      changed from its reset value and it's a reasonable assumption given
      that the firmware has never entered HYP mode.
      
      Note that it's been said that on ARMv8 systems the firmware and
      kernel really can't be architected as described above.  That means
      using the physical timer like this really only makes sense for ARMv7
      systems.
      Signed-off-by: NDoug Anderson <dianders@chromium.org>
      Signed-off-by: NSonny Rao <sonnyrao@chromium.org>
      Reviewed-by: NMark Rutland <mark.rutland@arm.com>
      Acked-by: NDaniel Lezcano <daniel.lezcano@linaro.org>
      Acked-by: NCatalin Marinas <catalin.marinas@arm.com>
      Signed-off-by: NOlof Johansson <olof@lixom.net>
      65b5732d
  5. 02 12月, 2014 3 次提交
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  13. 20 11月, 2014 1 次提交