qemu/vexpress-a9: Discover RAM size.

Probe RAM to find its size instead of hardcoding 1024M.
Also properly export it to memory map.

Change-Id: Ib411f0a068bd247a9e0cd0a59689a3896921483e
Signed-off-by: Vladimir Serbinenko <phcoder@gmail.com>
Reviewed-on: https://review.coreboot.org/13754
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>

src/mainboard/emulation/qemu-armv7/Kconfig

@@ -49,8 +49,4 @@ config MAINBOARD_VENDOR
 	string
 	default "ARM Ltd."
 
-config DRAM_SIZE_MB
-	int
-	default 1024
-
 endif #  BOARD_EMULATION_QEMU_ARMV7

src/mainboard/emulation/qemu-armv7/cbmem.c

@@ -14,8 +14,52 @@
 #include <stddef.h>
 #include <cbmem.h>
 #include <symbols.h>
+#include <arch/io.h>
+#include "mainboard.h"
+
+#define PATTERN1 0x55
+#define PATTERN2 0xaa
+
+/* Returns 1 if mebibyte mb is present and 0 otherwise.  */
+static int probe_mb(int mb)
+{
+	char *ptr = (char *) 0x60000000 + (mb << 20) + 0xfffff;
+	char old;
+	if (ptr < (char *) &_eprogram) {
+		/* Don't probe below _end to avoid accidentally clobering
+		   oneself.  */
+		return 1;
+	}
+
+	old = read8(ptr);
+	write8(ptr, PATTERN1);
+	if (read8(ptr) != PATTERN1)
+		return 0;
+	write8(ptr, PATTERN2);
+	if (read8(ptr) != PATTERN2)
+		return 0;
+	write8(ptr, old);
+	return 1;
+}
+
+int probe_ramsize(void)
+{
+	int i;
+	int discovered = 0;
+	static int saved_result;
+	if (saved_result)
+		return saved_result;
+	/* Compact binary search.  */
+	/* 1 GiB is the largest supported RAM by this machine.  */
+	for (i = 9; i >= 0; i--)
+		if (probe_mb(discovered | (1 << i)))
+			discovered |= (1 << i);
+	discovered++;
+	saved_result = discovered;
+	return discovered;
+}
 
 void *cbmem_top(void)
 {
-	return _dram + (CONFIG_DRAM_SIZE_MB << 20);
+	return _dram + (probe_ramsize() << 20);
 }

src/mainboard/emulation/qemu-armv7/mainboard.c

@@ -0,0 +1,40 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * Copyright (C) 2016 Vladimir Serbinenko <phcoder@gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 or, at your option, any later
+ * version of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <console/console.h>
+#include <device/device.h>
+#include <cbmem.h>
+#include <string.h>
+#include <halt.h>
+#include "mainboard.h"
+
+static void mainboard_enable(device_t dev)
+{
+	int discovered;
+	if (!dev) {
+		printk(BIOS_EMERG, "No dev0; die\n");
+		halt();
+	}
+
+	discovered = probe_ramsize();
+	printk(BIOS_DEBUG, "%d MiB of RAM discovered\n", discovered);
+	ram_resource(dev, 0, 0x60000000 >> 10, discovered << 10);
+	cbmem_recovery(0);
+}
+
+struct chip_operations mainboard_ops = {
+	.enable_dev = mainboard_enable,
+};

src/mainboard/emulation/qemu-armv7/mainboard.h

@@ -0,0 +1,23 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * Copyright (C) 2016 Vladimir Serbinenko <phcoder@gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 or, at your option, any later
+ * version of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#ifndef QEMU_ARMV7_MAINBOARD_H
+#define QEMU_ARMV7_MAINBOARD_H
+
+/* Returns RAM size in mebibytes.  */
+int probe_ramsize(void);
+
+#endif