MIPS: add detect_memory_region()

Add a generic way of detecting the available RAM. This function is based on the
implementation already used by ath79.

Signed-off-by: John Crispin <blogic@openwrt.org>
Patchwork: http://patchwork.linux-mips.org/patch/5178/

arch/mips/include/asm/bootinfo.h

@@ -104,6 +104,7 @@ struct boot_mem_map {
 extern struct boot_mem_map boot_mem_map;
 
 extern void add_memory_region(phys_t start, phys_t size, long type);
+extern void detect_memory_region(phys_t start, phys_t sz_min,  phys_t sz_max);
 
 extern void prom_init(void);
 extern void prom_free_prom_memory(void);

arch/mips/kernel/setup.c

@@ -23,6 +23,7 @@
 #include <linux/pfn.h>
 #include <linux/debugfs.h>
 #include <linux/kexec.h>
+#include <linux/sizes.h>
 
 #include <asm/addrspace.h>
 #include <asm/bootinfo.h>
@@ -77,6 +78,8 @@ EXPORT_SYMBOL(mips_io_port_base);
 static struct resource code_resource = { .name = "Kernel code", };
 static struct resource data_resource = { .name = "Kernel data", };
 
+static void *detect_magic __initdata = detect_memory_region;
+
 void __init add_memory_region(phys_t start, phys_t size, long type)
 {
 	int x = boot_mem_map.nr_map;
@@ -122,6 +125,25 @@ void __init add_memory_region(phys_t start, phys_t size, long type)
 	boot_mem_map.nr_map++;
 }
 
+void __init detect_memory_region(phys_t start, phys_t sz_min, phys_t sz_max)
+{
+	void *dm = &detect_magic;
+	phys_t size;
+
+	for (size = sz_min; size < sz_max; size <<= 1) {
+		if (!memcmp(dm, dm + size, sizeof(detect_magic)))
+			break;
+	}
+
+	pr_debug("Memory: %lluMB of RAM detected at 0x%llx (min: %lluMB, max: %lluMB)\n",
+		((unsigned long long) size) / SZ_1M,
+		(unsigned long long) start,
+		((unsigned long long) sz_min) / SZ_1M,
+		((unsigned long long) sz_max) / SZ_1M);
+
+	add_memory_region(start, size, BOOT_MEM_RAM);
+}
+
 static void __init print_memory_map(void)
 {
 	int i;