• Sonny Rao's avatar
    clocksource: arch_timer: Fix code to use physical timers when requested · 0b46b8a7
    Sonny Rao authored
    This is a bug fix for using physical arch timers when
    the arch_timer_use_virtual boolean is false.  It restores the
    arch_counter_get_cntpct() function after removal in
    
    0d651e4e "clocksource: arch_timer: use virtual counters"
    
    We need this on certain ARMv7 systems which 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 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)
    
    One example of such as system is RK3288 where it is much simpler to
    use the physical counter since 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.
    
    Fixes: 0d651e4e ("clocksource: arch_timer: use virtual counters")
    Cc: stable@vger.kernel.org
    Signed-off-by: default avatarSonny Rao <sonnyrao@chromium.org>
    Acked-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
    Acked-by: default avatarDaniel Lezcano <daniel.lezcano@linaro.org>
    Signed-off-by: default avatarOlof Johansson <olof@lixom.net>
    0b46b8a7
arm_arch_timer.c 20.2 KB