clocksource: arch_timer: Fix code to use physical timers when requested
commit 0b46b8a718c6e90910a1b1b0fe797be3c167e186 upstream.
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")
Signed-off-by: Sonny Rao <sonnyrao@chromium.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
index 43005d4..1fa2af9 100644
--- a/drivers/clocksource/arm_arch_timer.c
+++ b/drivers/clocksource/arm_arch_timer.c
@@ -462,7 +462,10 @@
/* Register the CP15 based counter if we have one */
if (type & ARCH_CP15_TIMER) {
- arch_timer_read_counter = arch_counter_get_cntvct;
+ if (arch_timer_use_virtual)
+ arch_timer_read_counter = arch_counter_get_cntvct;
+ else
+ arch_timer_read_counter = arch_counter_get_cntpct;
} else {
arch_timer_read_counter = arch_counter_get_cntvct_mem;