[PATCH V2 2/4] ARM: rpi_b: use bcm2835 mbox driver to get memory size

[Stephen Warren]

The firmware running on the bcm2835 SoC's VideoCore CPU determines how
much of the system RAM is available for use by the ARM CPU. Previously,
U-Boot assumed that only 128MB was available, since this was the
smallest value configured by any public firmware. However, we can now
query the actual value at run-time from the firmware using the mbox
property protocol.

Signed-off-by: Stephen Warren <swarren at wwwdotorg.org>
---
v2: Updated to use macros etc. added in v2 of mbox driver patch.
---
 board/raspberrypi/rpi_b/rpi_b.c |   21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/board/raspberrypi/rpi_b/rpi_b.c b/board/raspberrypi/rpi_b/rpi_b.c
index 688b0aa..3c654a1 100644
--- a/board/raspberrypi/rpi_b/rpi_b.c
+++ b/board/raspberrypi/rpi_b/rpi_b.c
@@ -15,13 +15,32 @@
  */
 
 #include <common.h>
+#include <asm/arch/mbox.h>
 #include <asm/global_data.h>
 
 DECLARE_GLOBAL_DATA_PTR;
 
+struct msg_get_arm_mem {
+	struct bcm2835_mbox_hdr hdr;
+	struct bcm2835_mbox_tag_get_arm_mem get_arm_mem;
+	u32 end_tag;
+};
+
 int dram_init(void)
 {
-	gd->ram_size = CONFIG_SYS_SDRAM_SIZE;
+	ALLOC_ALIGN_BUFFER(struct msg_get_arm_mem, msg, 1, 16);
+	int ret;
+
+	BCM2835_MBOX_INIT_HDR(msg);
+	BCM2835_MBOX_INIT_TAG(&msg->get_arm_mem, GET_ARM_MEMORY);
+
+	ret = bcm2835_mbox_call_prop(BCM2835_MBOX_PROP_CHAN, &msg->hdr);
+	if (ret) {
+		printf("bcm2835: Could not query ARM memory size\n");
+		return -1;
+	}
+
+	gd->ram_size = msg->get_arm_mem.body.resp.mem_size;
 
 	return 0;
 }
-- 
1.7.9.5