MIPS: JZ4740: setup: Autodetect physical memory.

Assume that the boot loader knows the physical memory of the system and
deduce that information from the contents of the SDRAM control register.
It is still possible to override with with the "mem=" parameter, but we
have a sensible default now.

arch/mips/jz4740/setup.c

@@ -1,5 +1,6 @@
 /*
  *  Copyright (C) 2009-2010, Lars-Peter Clausen <lars@metafoo.de>
+ *  Copyright (C) 2011, Maarten ter Huurne <maarten@treewalker.org>
  *  JZ4740 setup code
  *
  *  This program is free software; you can redistribute it and/or modify it
@@ -14,13 +15,44 @@
  */
 
 #include <linux/init.h>
+#include <linux/io.h>
 #include <linux/kernel.h>
 
+#include <asm/bootinfo.h>
+
+#include <asm/mach-jz4740/base.h>
+
 #include "reset.h"
 
+
+#define JZ4740_EMC_SDRAM_CTRL 0x80
+
+
+static void __init jz4740_detect_mem(void)
+{
+	void __iomem *jz_emc_base;
+	u32 ctrl, bus, bank, rows, cols;
+	phys_t size;
+
+	jz_emc_base = ioremap(JZ4740_EMC_BASE_ADDR, 0x100);
+	ctrl = readl(jz_emc_base + JZ4740_EMC_SDRAM_CTRL);
+	bus = 2 - ((ctrl >> 31) & 1);
+	bank = 1 + ((ctrl >> 19) & 1);
+	cols = 8 + ((ctrl >> 26) & 7);
+	rows = 11 + ((ctrl >> 20) & 3);
+	printk(KERN_DEBUG
+		"SDRAM preconfigured: bus:%u bank:%u rows:%u cols:%u\n",
+		bus, bank, rows, cols);
+	iounmap(jz_emc_base);
+
+	size = 1 << (bus + bank + cols + rows);
+	add_memory_region(0, size, BOOT_MEM_RAM);
+}
+
 void __init plat_mem_setup(void)
 {
 	jz4740_reset_init();
+	jz4740_detect_mem();
 }
 
 const char *get_system_type(void)