[PATCH 2/2] 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>
---
 board/raspberrypi/rpi_b/rpi_b.c |   20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/board/raspberrypi/rpi_b/rpi_b.c b/board/raspberrypi/rpi_b/rpi_b.c
index 688b0aa..88f8c58 100644
--- a/board/raspberrypi/rpi_b/rpi_b.c
+++ b/board/raspberrypi/rpi_b/rpi_b.c
@@ -15,13 +15,31 @@
  */
 
 #include <common.h>
+#include <asm/arch/mbox.h>
 #include <asm/global_data.h>
 
 DECLARE_GLOBAL_DATA_PTR;
 
 int dram_init(void)
 {
-	gd->ram_size = CONFIG_SYS_SDRAM_SIZE;
+	ALLOC_ALIGN_BUFFER(struct bcm2835_mbox_buf_get_arm_mem, buf, 1, 16);
+
+	memset(buf, 0, sizeof(*buf));
+	buf->hdr.buf_size = sizeof(*buf);
+	buf->hdr.code = BCM2835_MBOX_REQ_CODE;
+	buf->tag_hdr.tag = BCM2835_MBOX_TAG_GET_ARM_MEMORY;
+	buf->tag_hdr.val_buf_size = sizeof(buf->body);
+	buf->tag_hdr.val_len = sizeof(buf->body.req);
+
+	bcm2835_mbox_call_prop(BCM2835_MBOX_PROP_CHAN, &buf->hdr);
+
+	if ((buf->hdr.code != BCM2835_MBOX_RESP_CODE_SUCCESS) ||
+	    (!(buf->tag_hdr.val_len & BCM2835_MBOX_TAG_VAL_LEN_RESPONSE))) {
+		printf("BCM2835_MBOX_TAG_GET_ARM_MEMORY failed\n");
+		return -1;
+	}
+
+	gd->ram_size = buf->body.resp.mem_size;
 
 	return 0;
 }
-- 
1.7.9.5