ARM: digicolor: add low level debug support

Use the USART peripheral as UART for low level debug. Only the UA0 port is
currently supported.

Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Olof Johansson <olof@lixom.net>

arch/arm/Kconfig.debug

@@ -247,6 +247,13 @@ choice
 		  Say Y here if you want the debug print routines to direct
 		  their output to the serial port in the DC21285 (Footbridge).
 
+	config DEBUG_DIGICOLOR_UA0
+		bool "Kernel low-level debugging messages via Digicolor UA0"
+		depends on ARCH_DIGICOLOR
+		help
+		  Say Y here if you want the debug print routines to direct
+		  their output to the UA0 serial port in the CX92755.
+
 	config DEBUG_FOOTBRIDGE_COM1
 		bool "Kernel low-level debugging messages via footbridge 8250 at PCI COM1"
 		depends on FOOTBRIDGE
@@ -1255,6 +1262,7 @@ config DEBUG_LL_INCLUDE
 	default "debug/vt8500.S" if DEBUG_VT8500_UART0
 	default "debug/zynq.S" if DEBUG_ZYNQ_UART0 || DEBUG_ZYNQ_UART1
 	default "debug/bcm63xx.S" if DEBUG_UART_BCM63XX
+	default "debug/digicolor.S" if DEBUG_DIGICOLOR_UA0
 	default "mach/debug-macro.S"
 
 # Compatibility options for PL01x
@@ -1377,7 +1385,7 @@ config DEBUG_UART_PHYS
 		DEBUG_RMOBILE_SCIFA0 || DEBUG_RMOBILE_SCIFA1 || \
 		DEBUG_RMOBILE_SCIFA4 || DEBUG_S3C24XX_UART || \
 		DEBUG_UART_BCM63XX || DEBUG_ASM9260_UART || \
-		DEBUG_SIRFSOC_UART
+		DEBUG_SIRFSOC_UART || DEBUG_DIGICOLOR_UA0
 
 config DEBUG_UART_VIRT
 	hex "Virtual base address of debug UART"
@@ -1460,7 +1468,8 @@ config DEBUG_UART_VIRT
 	depends on DEBUG_LL_UART_8250 || DEBUG_LL_UART_PL01X || \
 		DEBUG_UART_8250 || DEBUG_UART_PL01X || DEBUG_MESON_UARTAO || \
 		DEBUG_MSM_UART || DEBUG_QCOM_UARTDM || DEBUG_S3C24XX_UART || \
-		DEBUG_UART_BCM63XX || DEBUG_ASM9260_UART || DEBUG_SIRFSOC_UART
+		DEBUG_UART_BCM63XX || DEBUG_ASM9260_UART || \
+		DEBUG_SIRFSOC_UART || DEBUG_DIGICOLOR_UA0
 
 config DEBUG_UART_8250_SHIFT
 	int "Register offset shift for the 8250 debug UART"

arch/arm/include/debug/digicolor.S

@@ -0,0 +1,35 @@
+/*
+ * Debugging macro include header for Conexant Digicolor USART
+ *
+ * Copyright (C) 2014 Paradox Innovation Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+*/
+
+#define UA0_STATUS	0x0742
+#define UA0_EMI_REC	0x0744
+
+#define UA0_STATUS_TX_READY	0x40
+
+#ifdef CONFIG_DEBUG_UART_PHYS
+		.macro	addruart, rp, rv, tmp
+		ldr	\rp, =CONFIG_DEBUG_UART_PHYS
+		ldr	\rv, =CONFIG_DEBUG_UART_VIRT
+		.endm
+#endif
+
+		.macro	senduart,rd,rx
+		strb	\rd, [\rx, #UA0_EMI_REC]
+		.endm
+
+		.macro	waituart,rd,rx
+		.endm
+
+	.macro	busyuart,rd,rx
+1001:		ldrb	\rd, [\rx, #UA0_STATUS]
+		tst	\rd, #UA0_STATUS_TX_READY
+		beq	1001b
+		.endm