[PATCH v5] clocksource: arch_timer: Fix code to use physical timers when requested
catalin.marinas at arm.com
Mon Nov 24 06:16:49 PST 2014
On Mon, Nov 24, 2014 at 09:01:36AM +0000, Daniel Lezcano wrote:
> On 11/24/2014 08:02 AM, 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 at vger.kernel.org
> > Signed-off-by: Sonny Rao <sonnyrao at chromium.org>
> > Acked-by: Olof Johansson <olof at lixom.net>
> are you ok with this patch ?
Acked-by: Catalin Marinas <catalin.marinas at arm.com>
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