arm: mvebu: remove dependency of SMP init on static I/O mapping

The ->smp_init_cpus() function is called very early during boot, at a
point where dynamic I/O mappings are not yet possible. However, in the
Armada 370/XP implementation of this function, we have to get the
number of CPUs. We used to do that by accessing a hardware register,
which requires relying on a static I/O mapping set up by
->map_io(). Not only this requires hardcoding a virtual address, but
it also prevents us from removing the static I/O mapping.

So this commit changes the way used to get the number of CPUs: we now
use the Device Tree, which is a representation of the hardware, and
provides us the number of available CPUs. This is also more accurate,
because it potentially allows to boot the Linux kernel on only a
number of CPUs given by the Device Tree, instead of unconditionally on
all CPUs.

As a consequence, the coherency_get_cpu_count() function becomes no
longer used, so we remove it.
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>

arch/arm/mach-mvebu/coherency.c

@@ -47,18 +47,6 @@ static struct of_device_id of_coherency_table[] = {
 	{ /* end of list */ },
 };
 
-#ifdef CONFIG_SMP
-int coherency_get_cpu_count(void)
-{
-	int reg, cnt;
-
-	reg = readl(coherency_base + COHERENCY_FABRIC_CFG_OFFSET);
-	cnt = (reg & 0xF) + 1;
-
-	return cnt;
-}
-#endif
-
 /* Function defined in coherency_ll.S */
 int ll_set_cpu_coherent(void __iomem *base_addr, unsigned int hw_cpu_id);
 

arch/arm/mach-mvebu/coherency.h

@@ -14,10 +14,6 @@
 #ifndef __MACH_370_XP_COHERENCY_H
 #define __MACH_370_XP_COHERENCY_H
 
-#ifdef CONFIG_SMP
-int coherency_get_cpu_count(void);
-#endif
-
 int set_cpu_coherent(int cpu_id, int smp_group_id);
 int coherency_init(void);
 

arch/arm/mach-mvebu/common.h

@@ -15,6 +15,8 @@
 #ifndef __ARCH_MVEBU_COMMON_H
 #define __ARCH_MVEBU_COMMON_H
 
+#define ARMADA_XP_MAX_CPUS 4
+
 void mvebu_restart(char mode, const char *cmd);
 
 void armada_370_xp_init_irq(void);

arch/arm/mach-mvebu/platsmp.c

@@ -88,8 +88,16 @@ static int __cpuinit armada_xp_boot_secondary(unsigned int cpu,
 
 static void __init armada_xp_smp_init_cpus(void)
 {
+	struct device_node *np;
 	unsigned int i, ncores;
-	ncores = coherency_get_cpu_count();
+
+	np = of_find_node_by_name(NULL, "cpus");
+	if (!np)
+		panic("No 'cpus' node found\n");
+
+	ncores = of_get_child_count(np);
+	if (ncores == 0 || ncores > ARMADA_XP_MAX_CPUS)
+		panic("Invalid number of CPUs in DT\n");
 
 	/* Limit possible CPUs to defconfig */
 	if (ncores > nr_cpu_ids) {