When CONFIG_SMP=y, timebase synchronization is required for mpc8572 when
the second kernel is started
arch/powerpc/kernel/smp.c:
int __cpu_up(unsigned int cpu, struct task_struct *tidle)
{
...
if (smp_ops->give_timebase)
smp_ops->give_timebase();
...
}
void start_secondary(void *unused)
{
...
if (smp_ops->take_timebase)
smp_ops->take_timebase();
...
}
When CONFIG_HOTPLUG_CPU=n and CONFIG_KEXEC_CORE=n,
smp_85xx_ops.give_timebase is NULL,
smp_85xx_ops.take_timebase is NULL,
As a result, the timebase is not synchronized.
test code:
for i in $(seq 1 3); do taskset 1 date; taskset 2 date; sleep 1; echo;done
log:
Sat Sep 25 18:50:00 CST 2021
Sat Sep 25 19:07:47 CST 2021
Sat Sep 25 18:50:01 CST 2021
Sat Sep 25 19:07:48 CST 2021
Sat Sep 25 18:50:02 CST 2021
Sat Sep 25 19:07:49 CST 2021
Code snippet about give_timebase and take_timebase assignments:
arch/powerpc/platforms/85xx/smp.c:
#ifdef CONFIG_HOTPLUG_CPU
#ifdef CONFIG_FSL_CORENET_RCPM
fsl_rcpm_init();
#endif
#ifdef CONFIG_FSL_PMC
mpc85xx_setup_pmc();
#endif
if (qoriq_pm_ops) {
smp_85xx_ops.give_timebase = mpc85xx_give_timebase;
smp_85xx_ops.take_timebase = mpc85xx_take_timebase;
config dependency:
FSL_CORENET_RCPM depends on the PPC_E500MC.
FSL_PMC depends on SUSPEND.
SUSPEND depends on ARCH_SUSPEND_POSSIBLE.
ARCH_SUSPEND_POSSIBLE depends on !PPC_E500MC.
CONFIG_HOTPLUG_CPU and CONFIG_FSL_PMC require the timebase function, but
the timebase should not depend on CONFIG_HOTPLUG_CPU and CONFIG_FSL_PMC.
Therefore, adjust the macro control range. Ensure that the corresponding
timebase hook function is not empty when the dtsi node is configured.
-----
changes in v2:
1. add new patch: "powerpc:85xx:Fix oops when mpc85xx_smp_guts_ids node
cannot be found"
2. Using !CONFIG_FSL_CORENET_RCPM to manage the timebase code of !PPC_E500MC
v1:
https://lore.kernel.org/lkml/20210926025144.55674-1-nixiaoming@xxxxxxxxxx
------
Xiaoming Ni (2):
powerpc:85xx:Fix oops when mpc85xx_smp_guts_ids node cannot be found
powerpc:85xx: fix timebase sync issue when CONFIG_HOTPLUG_CPU=n
arch/powerpc/platforms/85xx/Makefile | 4 +++-
arch/powerpc/platforms/85xx/mpc85xx_pm_ops.c | 7 +++++--
arch/powerpc/platforms/85xx/smp.c | 12 ++++++------
3 files changed, 14 insertions(+), 9 deletions(-)
--
2.27.0
