powerpc/fsl-booke-64: Allow booting from the secondary thread

This allows SMP kernels to work as kdump crash kernels.  While crash
kernels don't really need to be SMP, this prevents things from breaking
if a user does it anyway (which is not something you want to only find
out once the main kernel has crashed in the field, especially if
whether it works or not depends on which cpu crashed).
Signed-off-by: Scott Wood <scottwood@freescale.com>

arch/powerpc/platforms/85xx/smp.c

@@ -173,15 +173,22 @@ static inline u32 read_spin_table_addr_l(void *spin_table)
 static void wake_hw_thread(void *info)
 {
 	void fsl_secondary_thread_init(void);
-	unsigned long imsr1, inia1;
+	unsigned long imsr, inia;
 	int nr = *(const int *)info;
 
-	imsr1 = MSR_KERNEL;
-	inia1 = *(unsigned long *)fsl_secondary_thread_init;
-
-	mttmr(TMRN_IMSR1, imsr1);
-	mttmr(TMRN_INIA1, inia1);
+	imsr = MSR_KERNEL;
+	inia = *(unsigned long *)fsl_secondary_thread_init;
+
+	if (cpu_thread_in_core(nr) == 0) {
+		/* For when we boot on a secondary thread with kdump */
+		mttmr(TMRN_IMSR0, imsr);
+		mttmr(TMRN_INIA0, inia);
+		mtspr(SPRN_TENS, TEN_THREAD(0));
+	} else {
+		mttmr(TMRN_IMSR1, imsr);
+		mttmr(TMRN_INIA1, inia);
 		mtspr(SPRN_TENS, TEN_THREAD(1));
+	}
 
 	smp_generic_kick_cpu(nr);
 }
@@ -224,6 +231,12 @@ static int smp_85xx_kick_cpu(int nr)
 
 		smp_call_function_single(primary, wake_hw_thread, &nr, 0);
 		return 0;
+	} else if (cpu_thread_in_core(boot_cpuid) != 0 &&
+		   cpu_first_thread_sibling(boot_cpuid) == nr) {
+		if (WARN_ON_ONCE(!cpu_has_feature(CPU_FTR_SMT)))
+			return -ENOENT;
+
+		smp_call_function_single(boot_cpuid, wake_hw_thread, &nr, 0);
 	}
 #endif