powerpc: Add smp_generic_cpu_bootable

Cell and PSeries both implemented their own versions of a
cpu_bootable smp_op which do the same thing (well, the PSeries
one has support for more than 2 threads). Copy the PSeries one
to generic code, and rename it smp_generic_cpu_bootable.
Signed-off-by: Andy Fleming <afleming@freescale.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/include/asm/smp.h

@@ -186,6 +186,8 @@ extern int smt_enabled_at_boot;
 extern int smp_mpic_probe(void);
 extern void smp_mpic_setup_cpu(int cpu);
 extern int smp_generic_kick_cpu(int nr);
+extern int smp_generic_cpu_bootable(unsigned int nr);
+
 
 extern void smp_generic_give_timebase(void);
 extern void smp_generic_take_timebase(void);

arch/powerpc/kernel/smp.c

@@ -81,6 +81,28 @@ int smt_enabled_at_boot = 1;
 
 static void (*crash_ipi_function_ptr)(struct pt_regs *) = NULL;
 
+/*
+ * Returns 1 if the specified cpu should be brought up during boot.
+ * Used to inhibit booting threads if they've been disabled or
+ * limited on the command line
+ */
+int smp_generic_cpu_bootable(unsigned int nr)
+{
+	/* Special case - we inhibit secondary thread startup
+	 * during boot if the user requests it.
+	 */
+	if (system_state == SYSTEM_BOOTING && cpu_has_feature(CPU_FTR_SMT)) {
+		if (!smt_enabled_at_boot && cpu_thread_in_core(nr) != 0)
+			return 0;
+		if (smt_enabled_at_boot
+		    && cpu_thread_in_core(nr) >= smt_enabled_at_boot)
+			return 0;
+	}
+
+	return 1;
+}
+
+
 #ifdef CONFIG_PPC64
 int smp_generic_kick_cpu(int nr)
 {