MIPS: ath25: add early printk support

Signed-off-by: Sergey Ryazanov <ryazanov.s.a@gmail.com>
Cc: Linux MIPS <linux-mips@linux-mips.org>
Patchwork: https://patchwork.linux-mips.org/patch/8241/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/Kconfig

@@ -107,6 +107,7 @@ config ATH25
 	select SYS_HAS_CPU_MIPS32_R1
 	select SYS_SUPPORTS_BIG_ENDIAN
 	select SYS_SUPPORTS_32BIT_KERNEL
+	select SYS_HAS_EARLY_PRINTK
 	help
 	  Support for Atheros AR231x and Atheros AR531x based boards
 

arch/mips/ath25/Makefile

@@ -10,5 +10,7 @@
 
 obj-y += board.o prom.o devices.o
 
+obj-$(CONFIG_EARLY_PRINTK) += early_printk.o
+
 obj-$(CONFIG_SOC_AR5312) += ar5312.o
 obj-$(CONFIG_SOC_AR2315) += ar2315.o

arch/mips/ath25/early_printk.c

+/*
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * Copyright (C) 2010 Gabor Juhos <juhosg@openwrt.org>
+ */
+
+#include <linux/mm.h>
+#include <linux/io.h>
+#include <linux/serial_reg.h>
+
+#include "devices.h"
+#include "ar2315_regs.h"
+#include "ar5312_regs.h"
+
+static inline void prom_uart_wr(void __iomem *base, unsigned reg,
+				unsigned char ch)
+{
+	__raw_writel(ch, base + 4 * reg);
+}
+
+static inline unsigned char prom_uart_rr(void __iomem *base, unsigned reg)
+{
+	return __raw_readl(base + 4 * reg);
+}
+
+void prom_putchar(unsigned char ch)
+{
+	static void __iomem *base;
+
+	if (unlikely(base == NULL)) {
+		if (is_ar2315())
+			base = (void __iomem *)(KSEG1ADDR(AR2315_UART0_BASE));
+		else
+			base = (void __iomem *)(KSEG1ADDR(AR5312_UART0_BASE));
+	}
+
+	while ((prom_uart_rr(base, UART_LSR) & UART_LSR_THRE) == 0)
+		;
+	prom_uart_wr(base, UART_TX, ch);
+	while ((prom_uart_rr(base, UART_LSR) & UART_LSR_THRE) == 0)
+		;
+}