Re: [PATCH v4] clocksource: arch_timer: Fix code to use physical timers when requested

From: Maxime Ripard
Date: Thu Nov 20 2014 - 03:50:13 EST


On Wed, Oct 08, 2014 at 12:38:57AM -0700, Sonny Rao wrote:
> 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: 0d651e4e65e9 ("clocksource: arch_timer: use virtual counters")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Sonny Rao <sonnyrao@xxxxxxxxxxxx>
> Acked-by: Olof Johansson <olof@xxxxxxxxx>

Has this been merged yet?

If not, you can add my Tested-by, it makes the Allwinner A31 boot
flawlessly with the arch timers (together with the patch "clocksource:
arch_timer: Allow the device tree to specify uninitialized timer



Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering

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