[PATCH] powerpc/85xx: fix oops when CONFIG_FSL_PMC=n

When CONFIG_FSL_PMC is set to n, no value is assigned to cpu_up_prepare
 in the mpc85xx_pm_ops structure. As a result, oops is triggered in
 smp_85xx_start_cpu().

	[    0.627233] smp: Bringing up secondary CPUs ...
	[    0.681659] kernel tried to execute user page (0) - exploit attempt? (uid: 0)
	[    0.766618] BUG: Unable to handle kernel instruction fetch (NULL pointer?)
	[    0.848899] Faulting instruction address: 0x00000000
	[    0.908273] Oops: Kernel access of bad area, sig: 11 [#1]
	...
	[    1.758220] NIP [00000000] 0x0
	[    1.794688] LR [c0021d2c] smp_85xx_kick_cpu+0xe8/0x568
	[    1.856126] Call Trace:
	[    1.885295] [c1051da8] [c0021cb8] smp_85xx_kick_cpu+0x74/0x568 (unreliable)
	[    1.968633] [c1051de8] [c0011460] __cpu_up+0xc0/0x228
	[    2.029038] [c1051e18] [c0031bbc] bringup_cpu+0x30/0x224
	[    2.092572] [c1051e48] [c0031f3c] cpu_up.constprop.0+0x180/0x33c
	[    2.164443] [c1051e88] [c00322e8] bringup_nonboot_cpus+0x88/0xc8
	[    2.236326] [c1051eb8] [c07e67bc] smp_init+0x30/0x78
	[    2.295698] [c1051ed8] [c07d9e28] kernel_init_freeable+0x118/0x2a8
	[    2.369641] [c1051f18] [c00032d8] kernel_init+0x14/0x124
	[    2.433176] [c1051f38] [c0010278] ret_from_kernel_thread+0x14/0x1c

Fixes: c45361abb9185b ("powerpc/85xx: fix timebase sync issue when
 CONFIG_HOTPLUG_CPU=n")
Link: https://lore.kernel.org/lkml/CANA18Uyba4kMJQrbCSZVTFep2Exe5izE45whNJgwwUvNSEcNLg@mail.gmail.com/ (local)
Reported-by: Martin Kennedy <redacted>
Signed-off-by: Xiaoming Ni <redacted>
Tested-by: Martin Kennedy <redacted>
Cc: stable@vger.kernel.org
---
 arch/powerpc/platforms/85xx/smp.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/platforms/85xx/smp.c b/arch/powerpc/platforms/85xx/smp.c
index 83f4a6389a28..d7081e9af65c 100644
--- a/arch/powerpc/platforms/85xx/smp.c
+++ b/arch/powerpc/platforms/85xx/smp.c

@@ -220,7 +220,7 @@ static int smp_85xx_start_cpu(int cpu)
 	local_irq_save(flags);
 	hard_irq_disable();
 
-	if (qoriq_pm_ops)
+	if (qoriq_pm_ops && qoriq_pm_ops->cpu_up_prepare)
 		qoriq_pm_ops->cpu_up_prepare(cpu);
 
 	/* if cpu is not spinning, reset it */

@@ -292,7 +292,7 @@ static int smp_85xx_kick_cpu(int nr)
 		booting_thread_hwid = cpu_thread_in_core(nr);
 		primary = cpu_first_thread_sibling(nr);
 
-		if (qoriq_pm_ops)
+		if (qoriq_pm_ops && qoriq_pm_ops->cpu_up_prepare)
 			qoriq_pm_ops->cpu_up_prepare(nr);
 
 		/*

-- 
2.27.0