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

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: <redacted> #v4.6
Signed-off-by: Xiaoming Ni <redacted>
---
 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

On 2021/9/26 10:51, Xiaoming Ni wrote:

83 more quoted lines

I found inconsistent time values on different CPUs on my mpc8572 and used this patch to fix it.
But today I found out in ppc64 testing that this patch causes the system to trigger oops in the function mpc85xx_freeze_time_base(): the variable "guts" is a null pointer.

I'm sorry to bother you.
I'll fix it and resend v2 later,

Thanks
Xiaoming Ni

When the field described in mpc85xx_smp_guts_ids[] is not configured in
 dtb, the mpc85xx_setup_pmc() does not assign a value to the "guts"
 variable. As a result, the oops is triggered when
 mpc85xx_freeze_time_base() is executed.

Fixes:56f1ba280719 ("powerpc/mpc85xx: refactor the PM operations")
Cc: <redacted> #v4.6
Signed-off-by: Xiaoming Ni <redacted>
---
 arch/powerpc/platforms/85xx/mpc85xx_pm_ops.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/powerpc/platforms/85xx/mpc85xx_pm_ops.c b/arch/powerpc/platforms/85xx/mpc85xx_pm_ops.c
index 7c0133f558d0..ffa8a7a6a2db 100644
--- a/arch/powerpc/platforms/85xx/mpc85xx_pm_ops.c
+++ b/arch/powerpc/platforms/85xx/mpc85xx_pm_ops.c

@@ -94,9 +94,8 @@ int __init mpc85xx_setup_pmc(void)
 			pr_err("Could not map guts node address\n");
 			return -ENOMEM;
 		}
+		qoriq_pm_ops = &mpc85xx_pm_ops;
 	}
 
-	qoriq_pm_ops = &mpc85xx_pm_ops;
-
 	return 0;
 }

-- 
2.27.0

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

42 more lines

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: <redacted> #v4.6
Signed-off-by: Xiaoming Ni <redacted>
---
 arch/powerpc/platforms/85xx/Makefile         |  4 +++-
 arch/powerpc/platforms/85xx/mpc85xx_pm_ops.c |  4 ++++
 arch/powerpc/platforms/85xx/smp.c            | 12 ++++++------
 3 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/arch/powerpc/platforms/85xx/Makefile b/arch/powerpc/platforms/85xx/Makefile
index 60e4e97a929d..260fbad7967b 100644
--- a/arch/powerpc/platforms/85xx/Makefile
+++ b/arch/powerpc/platforms/85xx/Makefile

@@ -3,7 +3,9 @@
 # Makefile for the PowerPC 85xx linux kernel.
 #
 obj-$(CONFIG_SMP) += smp.o
-obj-$(CONFIG_FSL_PMC)		  += mpc85xx_pm_ops.o
+ifneq ($(CONFIG_FSL_CORENET_RCPM),y)
+obj-$(CONFIG_SMP) += mpc85xx_pm_ops.o
+endif
 
 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 ffa8a7a6a2db..4a8af80011a6 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..83f4a6389a28 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();

@@ -495,21 +495,21 @@ void __init mpc85xx_smp_init(void)
 		smp_85xx_ops.probe = NULL;
 	}
 
-#ifdef CONFIG_HOTPLUG_CPU
 #ifdef CONFIG_FSL_CORENET_RCPM
+	/* Assign a value to qoriq_pm_ops on PPC_E500MC */
 	fsl_rcpm_init();
-#endif
-
-#ifdef CONFIG_FSL_PMC
+#else
+	/* Assign a value to qoriq_pm_ops on !PPC_E500MC */
 	mpc85xx_setup_pmc();
 #endif
 	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

On Wed, 29 Sep 2021 11:36:44 +0800, Xiaoming Ni wrote:

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();
		...
	}

[...]

Applied to powerpc/next.

[1/2] powerpc:85xx:Fix oops when mpc85xx_smp_guts_ids node cannot be found
      https://git.kernel.org/powerpc/c/3c2172c1c47b4079c29f0e6637d764a99355ebcd
[2/2] powerpc:85xx: fix timebase sync issue when CONFIG_HOTPLUG_CPU=n
      https://git.kernel.org/powerpc/c/c45361abb9185b1e172bd75eff51ad5f601ccae4

cheers