[PATCH] powerpc:85xx: fix timebase sync issue when CONFIG_HOTPLUG_CPU=n

From: Xiaoming Ni
Date: Sat Sep 25 2021 - 22:52:07 EST


When CONFIG_SMP=y, timebase synchronization is required 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.

Timebase synchronization does not depend on CONFIG_HOTPLUG_CPU.

Fixes: 56f1ba280719 ("powerpc/mpc85xx: refactor the PM operations")
Cc: stable@xxxxxxxxxxxxxxx #v4.6
Signed-off-by: Xiaoming Ni <nixiaoming@xxxxxxxxxx>
---
arch/powerpc/platforms/85xx/Makefile | 2 +-
arch/powerpc/platforms/85xx/mpc85xx_pm_ops.c | 4 ++++
arch/powerpc/platforms/85xx/smp.c | 9 ++++-----
3 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/arch/powerpc/platforms/85xx/Makefile b/arch/powerpc/platforms/85xx/Makefile
index 60e4e97a929d..71ce1f6b6966 100644
--- a/arch/powerpc/platforms/85xx/Makefile
+++ b/arch/powerpc/platforms/85xx/Makefile
@@ -3,7 +3,7 @@
# Makefile for the PowerPC 85xx linux kernel.
#
obj-$(CONFIG_SMP) += smp.o
-obj-$(CONFIG_FSL_PMC) += mpc85xx_pm_ops.o
+obj-$(CONFIG_SMP) += mpc85xx_pm_ops.o

obj-y += common.o

diff --git a/arch/powerpc/platforms/85xx/mpc85xx_pm_ops.c b/arch/powerpc/platforms/85xx/mpc85xx_pm_ops.c
index 7c0133f558d0..a5656b3e9701 100644
--- a/arch/powerpc/platforms/85xx/mpc85xx_pm_ops.c
+++ b/arch/powerpc/platforms/85xx/mpc85xx_pm_ops.c
@@ -17,6 +17,7 @@

static struct ccsr_guts __iomem *guts;

+#ifdef CONFIG_FSL_PMC
static void mpc85xx_irq_mask(int cpu)
{

@@ -49,6 +50,7 @@ static void mpc85xx_cpu_up_prepare(int cpu)
{

}
+#endif

static void mpc85xx_freeze_time_base(bool freeze)
{
@@ -76,10 +78,12 @@ static const struct of_device_id mpc85xx_smp_guts_ids[] = {

static const struct fsl_pm_ops mpc85xx_pm_ops = {
.freeze_time_base = mpc85xx_freeze_time_base,
+#ifdef CONFIG_FSL_PMC
.irq_mask = mpc85xx_irq_mask,
.irq_unmask = mpc85xx_irq_unmask,
.cpu_die = mpc85xx_cpu_die,
.cpu_up_prepare = mpc85xx_cpu_up_prepare,
+#endif
};

int __init mpc85xx_setup_pmc(void)
diff --git a/arch/powerpc/platforms/85xx/smp.c b/arch/powerpc/platforms/85xx/smp.c
index c6df294054fe..349298cd9671 100644
--- a/arch/powerpc/platforms/85xx/smp.c
+++ b/arch/powerpc/platforms/85xx/smp.c
@@ -40,7 +40,6 @@ struct epapr_spin_table {
u32 pir;
};

-#ifdef CONFIG_HOTPLUG_CPU
static u64 timebase;
static int tb_req;
static int tb_valid;
@@ -112,6 +111,7 @@ static void mpc85xx_take_timebase(void)
local_irq_restore(flags);
}

+#ifdef CONFIG_HOTPLUG_CPU
static void smp_85xx_cpu_offline_self(void)
{
unsigned int cpu = smp_processor_id();
@@ -499,17 +499,16 @@ void __init mpc85xx_smp_init(void)
#ifdef CONFIG_FSL_CORENET_RCPM
fsl_rcpm_init();
#endif
-
-#ifdef CONFIG_FSL_PMC
- mpc85xx_setup_pmc();
#endif
+ mpc85xx_setup_pmc();
if (qoriq_pm_ops) {
smp_85xx_ops.give_timebase = mpc85xx_give_timebase;
smp_85xx_ops.take_timebase = mpc85xx_take_timebase;
+#ifdef CONFIG_HOTPLUG_CPU
smp_85xx_ops.cpu_offline_self = smp_85xx_cpu_offline_self;
smp_85xx_ops.cpu_die = qoriq_cpu_kill;
- }
#endif
+ }
smp_ops = &smp_85xx_ops;

#ifdef CONFIG_KEXEC_CORE
--
2.27.0