[PATCH 8/8] mx25 3ds: add support for boot from UART

[Baruch Siach]

For details of the UART protocol see the i.MX25 Reference Manual, section 7.8
"Serial Download protocol".

Signed-off-by: Baruch Siach <baruch at tkos.co.il>
---
 arch/arm/mach-imx/Kconfig                    |    5 +++++
 board/freescale-mx25-3-stack/3stack.c        |    4 ++++
 board/freescale-mx25-3-stack/lowlevel_init.S |    5 +++++
 3 files changed, 14 insertions(+), 0 deletions(-)

diff --git a/arch/arm/mach-imx/Kconfig b/arch/arm/mach-imx/Kconfig
index 419daab..40cebed 100644
--- a/arch/arm/mach-imx/Kconfig
+++ b/arch/arm/mach-imx/Kconfig
@@ -319,6 +319,11 @@ config FREESCALE_MX25_3STACK_SDRAM_64MB_DDR2
 config FREESCALE_MX25_3STACK_SDRAM_128MB_MDDR
 	bool "128 MB (mDDR)"
 endchoice
+
+config FREESCALE_MX25_3STACK_UART_BOOT
+	bool "Boot from UART"
+	depends on ARCH_IMX_INTERNAL_BOOT
+
 endif
 endmenu
 
diff --git a/board/freescale-mx25-3-stack/3stack.c b/board/freescale-mx25-3-stack/3stack.c
index a657a47..081487a 100644
--- a/board/freescale-mx25-3-stack/3stack.c
+++ b/board/freescale-mx25-3-stack/3stack.c
@@ -44,7 +44,11 @@ extern unsigned long _stext;
 
 void __naked __flash_header_start go(void)
 {
+#if defined CONFIG_FREESCALE_MX25_3STACK_UART_BOOT
+	__asm__ (".word	exception_vectors\n");
+#else
 	__asm__ __volatile__("b exception_vectors\n");
+#endif
 }
 
 struct imx_dcd_entry __dcd_entry_0x400 dcd_entry[] = {
diff --git a/board/freescale-mx25-3-stack/lowlevel_init.S b/board/freescale-mx25-3-stack/lowlevel_init.S
index 73bb147..b65a070 100644
--- a/board/freescale-mx25-3-stack/lowlevel_init.S
+++ b/board/freescale-mx25-3-stack/lowlevel_init.S
@@ -73,6 +73,11 @@ board_init_lowlevel:
 	writel(0x000FDFFF, IMX_CCM_BASE + CCM_CGCR2)
 	writel(0x0000FEFF, IMX_CCM_BASE + MX25_CCM_MCR)
 
+#if defined CONFIG_FREESCALE_MX25_3STACK_UART_BOOT
+	/* initialize CCM_CCTL, ARM clk = 400, AHB clk = 133 */
+	writel(0x20034000, IMX_CCM_BASE + 0x8);
+#endif
+
 	/* Skip SDRAM initialization if we run from RAM */
 	cmp	pc, #0x80000000
 	bls	1f
-- 
1.7.1