[U-Boot] [U-boot][PATCH v2] keystone2: add support for UART download

[Vitaly Andrianov]

Currently to flash u-boot image onto NAND or SPI NOR flash, very first
time user need to use Code Composer Studio (CCS). This is cumbersome for
an user not familiar with CCS. This patch add simpler procedure using
uart boot mode for K2 EVMs.

When UART bootmode is set and board is rebooted, the ROM boot loader
transfers the image at the beginning of the internal RAM. After the
transfer is complete the boot-loader sets the PC to the first internal RAM
address 0x0c000000. The u-boot.bin is linked to the address 0x0c001000.

In order to use the u-boot.bin as an image for UART download, we need to
add 4K zeros prefix that act as 1K NOP instructions before reaching
0xc001000.

Signed-off-by: Vitaly Andrianov <vitalya at ti.com>
Acked-by: Murali Karicheri <m-karicheri2 at ti.com>
Tested-by: Murali Karicheri <m-karicheri2 at ti.com>
---
Changes in V2:
	- removed extra EOL
	- "MSMC" replaced by "internal RAM" in the commit message

 Makefile                |  6 ++++++
 board/ti/ks2_evm/README | 15 +++++++++++++++
 2 files changed, 21 insertions(+)

diff --git a/Makefile b/Makefile
index 36a9a28..7a86cac 100644
--- a/Makefile
+++ b/Makefile
@@ -940,6 +940,12 @@ u-boot-nand.gph: u-boot.bin FORCE
 	$(call if_changed,mkimage)
 	@dd if=/dev/zero bs=8 count=1 2>/dev/null >> $@
 
+u-boot.uart.pad:
+	@dd if=/dev/zero bs=4 count=1024 2>/dev/null > $@
+
+u-boot.uart: u-boot.uart.pad u-boot.bin FORCE
+	$(call if_changed,cat)
+
 # x86 uses a large ROM. We fill it with 0xff, put the 16-bit stuff (including
 # reset vector) at the top, Intel ME descriptor at the bottom, and U-Boot in
 # the middle.
diff --git a/board/ti/ks2_evm/README b/board/ti/ks2_evm/README
index 9ee90a4..7e2e096 100644
--- a/board/ti/ks2_evm/README
+++ b/board/ti/ks2_evm/README
@@ -81,6 +81,21 @@ To build u-boot-nand.gph
   >make k2hk_evm_defconfig
   >make u-boot-nand.gph
 
+To build u-boot.uart
+  >make k2hk_evm_defconfig
+  >make u-boot.uart
+
+Load and Run U-Boot on keystone EVMs using UART download
+========================================================
+
+Open BMC and regular UART terminals.
+
+1. On the regular UART port start xmodem transfer of the u-boot.uart
+2. Using BMC terminal set the ARM-UART bootmode and reboot the EVM
+   BMC> bootmode #4
+   MBC> reboot
+3. When xmodem is complete you should see the u-boot starts on the UART port
+
 Load and Run U-Boot on keystone EVMs using CCS
 =========================================
 
-- 
1.9.1