[MIPS] SMP: Fix initialization order bug.

A recent change requires cpu_possible_map to be initialized before
smp_sched_init() but most MIPS platforms were initializing their
processors in the prom_prepare_cpus callback of smp_prepare_cpus.  The
simple fix of calling prom_prepare_cpus from one of the earlier SMP
initialization hooks doesn't work well either since IPIs may require
init_IRQ() to have completed, so bit the bullet and split
prom_prepare_cpus into two initialization functions, plat_smp_setup
which is called early from setup_arch and plat_prepare_cpus called where
prom_prepare_cpus used to be called.
    
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/kernel/setup.c

@@ -540,6 +540,9 @@ void __init setup_arch(char **cmdline_p)
 	sparse_init();
 	paging_init();
 	resource_init();
+#ifdef CONFIG_SMP
+	plat_smp_setup();
+#endif
 }
 
 int __init fpu_disable(char *s)

arch/mips/kernel/smp.c

@@ -236,7 +236,7 @@ void __init smp_prepare_cpus(unsigned int max_cpus)
 	init_new_context(current, &init_mm);
 	current_thread_info()->cpu = 0;
 	smp_tune_scheduling();
-	prom_prepare_cpus(max_cpus);
+	plat_prepare_cpus(max_cpus);
 }
 
 /* preload SMP state for boot cpu */

arch/mips/kernel/smp_mt.c

@@ -143,7 +143,7 @@ static struct irqaction irq_call = {
  * Make sure all CPU's are in a sensible state before we boot any of the
  * secondarys
  */
-void prom_prepare_cpus(unsigned int max_cpus)
+void plat_smp_setup(void)
 {
 	unsigned long val;
 	int i, num;
@@ -179,11 +179,9 @@ void prom_prepare_cpus(unsigned int max_cpus)
 				write_vpe_c0_vpeconf0(tmp);
 
 				/* Record this as available CPU */
-				if (i < max_cpus) {
-					cpu_set(i, phys_cpu_present_map);
-					__cpu_number_map[i]	= ++num;
-					__cpu_logical_map[num]	= i;
-				}
+				cpu_set(i, phys_cpu_present_map);
+				__cpu_number_map[i]	= ++num;
+				__cpu_logical_map[num]	= i;
 			}
 
 			/* disable multi-threading with TC's */
@@ -241,7 +239,10 @@ void prom_prepare_cpus(unsigned int max_cpus)
 		set_vi_handler (MIPS_CPU_IPI_RESCHED_IRQ, ipi_resched_dispatch);
 		set_vi_handler (MIPS_CPU_IPI_CALL_IRQ, ipi_call_dispatch);
 	}
+}
 
+void __init plat_prepare_cpus(unsigned int max_cpus)
+{
 	cpu_ipi_resched_irq = MIPSCPU_INT_BASE + MIPS_CPU_IPI_RESCHED_IRQ;
 	cpu_ipi_call_irq = MIPSCPU_INT_BASE + MIPS_CPU_IPI_CALL_IRQ;
 

arch/mips/pmc-sierra/yosemite/smp.c

@@ -50,37 +50,25 @@ void __init prom_grab_secondary(void)
  * We don't want to start the secondary CPU yet nor do we have a nice probing
  * feature in PMON so we just assume presence of the secondary core.
  */
-static char maxcpus_string[] __initdata =
-	KERN_WARNING "max_cpus set to 0; using 1 instead\n";
-
-void __init prom_prepare_cpus(unsigned int max_cpus)
+void __init plat_smp_setup(void)
 {
-	int enabled = 0, i;
-
-	if (max_cpus == 0) {
-		printk(maxcpus_string);
-		max_cpus = 1;
-	}
+	int i;
 
 	cpus_clear(phys_cpu_present_map);
 
 	for (i = 0; i < 2; i++) {
-		if (i == max_cpus)
-			break;
-
-		/*
-		 * The boot CPU
-		 */
 		cpu_set(i, phys_cpu_present_map);
 		__cpu_number_map[i]	= i;
 		__cpu_logical_map[i]	= i;
-		enabled++;
 	}
+}
 
+void __init plat_prepare_cpus(unsigned int max_cpus)
+{
 	/*
 	 * Be paranoid.  Enable the IPI only if we're really about to go SMP.
 	 */
-	if (enabled > 1)
+	if (cpus_weight(cpu_possible_map))
 		set_c0_status(STATUSF_IP5);
 }
 

arch/mips/sgi-ip27/ip27-smp.c

@@ -140,7 +140,7 @@ static __init void intr_clear_all(nasid_t nasid)
 		REMOTE_HUB_CLR_INTR(nasid, i);
 }
 
-void __init prom_prepare_cpus(unsigned int max_cpus)
+void __init plat_smp_setup(void)
 {
 	cnodeid_t	cnode;
 
@@ -161,6 +161,11 @@ void __init prom_prepare_cpus(unsigned int max_cpus)
 	alloc_cpupda(0, 0);
 }
 
+void __init plat_prepare_cpus(unsigned int max_cpus)
+{
+	/* We already did everything necessary earlier */
+}
+
 /*
  * Launch a slave into smp_bootstrap().  It doesn't take an argument, and we
  * set sp to the kernel stack of the newly created idle process, gp to the proc

arch/mips/sibyte/cfe/smp.c

@@ -31,7 +31,7 @@
  *
  * Common setup before any secondaries are started
  */
-void __init prom_prepare_cpus(unsigned int max_cpus)
+void __init plat_smp_setup(void)
 {
 	int i, num;
 
@@ -40,14 +40,18 @@ void __init prom_prepare_cpus(unsigned int max_cpus)
 	__cpu_number_map[0] = 0;
 	__cpu_logical_map[0] = 0;
 
-	for (i=1, num=0; i<NR_CPUS; i++) {
+	for (i = 1, num = 0; i < NR_CPUS; i++) {
 		if (cfe_cpu_stop(i) == 0) {
 			cpu_set(i, phys_cpu_present_map);
 			__cpu_number_map[i] = ++num;
 			__cpu_logical_map[num] = i;
 		}
 	}
-	printk("Detected %i available secondary CPU(s)\n", num);
+	printk(KERN_INFO "Detected %i available secondary CPU(s)\n", num);
+}
+
+void __init plat_prepare_cpus(unsigned int max_cpus)
+{
 }
 
 /*

include/asm-mips/smp.h

@@ -58,7 +58,9 @@ static inline int num_booting_cpus(void)
 	return cpus_weight(cpu_callout_map);
 }
 
-/* These are defined by the board-specific code. */
+/*
+ * These are defined by the board-specific code.
+ */
 
 /*
  * Cause the function described by call_data to be executed on the passed
@@ -79,7 +81,12 @@ extern void prom_boot_secondary(int cpu, struct task_struct *idle);
 extern void prom_init_secondary(void);
 
 /*
- * Detect available CPUs, populate phys_cpu_present_map before smp_init
+ * Populate cpu_possible_map before smp_init, called from setup_arch.
+ */
+extern void plat_smp_setup(void);
+
+/*
+ * Called after init_IRQ but before __cpu_up.
  */
 extern void prom_prepare_cpus(unsigned int max_cpus);