ARM: rpi_b: detect board revision

Detect the board revision early during boot, and print the decoded
model name.

Eventually, this information can be used for tasks such as:
- Allowing/preventing USB device mode; some models have a USB device on-
  board so only host mode makes sense. Others connect the SoC directly
  to the USB connector, so device-mode might make sense.
- The on-board USB hub/Ethernet requires different GPIOs to enable it,
  although luckily the default appears to be fine so far.
- The compute module contains an on-board eMMC device, so we could store
  the environment there. Other models use an SD card and so don't support
  saving the environment (unless we store it in a file on the FAT boot
  partition...)

Set $fdtfile based on this information. At present, the mainline Linux
kernel doesn't contain a separate DTB for most models, but I hope that
will change soon.

Signed-off-by: Stephen Warren <swarren@wwwdotorg.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
Tested-by: Simon Glass <sjg@chromium.org>

1 files changed, 33 insertions, 0 deletions

diff --git a/arch/arm/include/asm/arch-bcm2835/mbox.h b/arch/arm/include/asm/arch-bcm2835/mbox.h
index 61f427d914..0289ba6a91 100644
--- a/arch/arm/include/asm/arch-bcm2835/mbox.h
+++ b/arch/arm/include/asm/arch-bcm2835/mbox.h
@@ -119,6 +119,39 @@ struct bcm2835_mbox_tag_hdr {
  * };
  */
 
+#define BCM2835_MBOX_TAG_GET_BOARD_REV	0x00010002
+
+/*
+ * 0x2..0xf from:
+ * http://raspberryalphaomega.org.uk/2013/02/06/automatic-raspberry-pi-board-revision-detection-model-a-b1-and-b2/
+ * http://www.raspberrypi.org/forums/viewtopic.php?f=63&t=32733
+ * 0x10, 0x11 from swarren's testing
+ */
+#define BCM2835_BOARD_REV_B_I2C0_2	0x2
+#define BCM2835_BOARD_REV_B_I2C0_3	0x3
+#define BCM2835_BOARD_REV_B_I2C1_4	0x4
+#define BCM2835_BOARD_REV_B_I2C1_5	0x5
+#define BCM2835_BOARD_REV_B_I2C1_6	0x6
+#define BCM2835_BOARD_REV_A_7		0x7
+#define BCM2835_BOARD_REV_A_8		0x8
+#define BCM2835_BOARD_REV_A_9		0x9
+#define BCM2835_BOARD_REV_B_REV2_d	0xd
+#define BCM2835_BOARD_REV_B_REV2_e	0xe
+#define BCM2835_BOARD_REV_B_REV2_f	0xf
+#define BCM2835_BOARD_REV_B_PLUS	0x10
+#define BCM2835_BOARD_REV_CM		0x11
+
+struct bcm2835_mbox_tag_get_board_rev {
+	struct bcm2835_mbox_tag_hdr tag_hdr;
+	union {
+		struct {
+		} req;
+		struct {
+			u32 rev;
+		} resp;
+	} body;
+};
+
 #define BCM2835_MBOX_TAG_GET_MAC_ADDRESS	0x00010003
 
 struct bcm2835_mbox_tag_get_mac_address {