1 files changed, 88 insertions, 0 deletions
diff --git a/arch/mips/ralink/early_printk.c b/arch/mips/ralink/early_printk.c
new file mode 100644
index 000000000..eb4fac25e
--- /dev/null
+++ b/arch/mips/ralink/early_printk.c
@@ -0,0 +1,88 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *
+ *  Copyright (C) 2011-2012 Gabor Juhos <juhosg@openwrt.org>
+ */
+
+#include <linux/io.h>
+#include <linux/serial_reg.h>
+
+#include <asm/addrspace.h>
+#include <asm/setup.h>
+
+#ifdef CONFIG_SOC_RT288X
+#define EARLY_UART_BASE		0x300c00
+#define CHIPID_BASE		0x300004
+#elif defined(CONFIG_SOC_MT7621)
+#define EARLY_UART_BASE		0x1E000c00
+#define CHIPID_BASE		0x1E000004
+#else
+#define EARLY_UART_BASE		0x10000c00
+#define CHIPID_BASE		0x10000004
+#endif
+
+#define MT7628_CHIP_NAME1	0x20203832
+
+#define UART_REG_TX		0x04
+#define UART_REG_LCR		0x0c
+#define UART_REG_LSR		0x14
+#define UART_REG_LSR_RT2880	0x1c
+
+static __iomem void *uart_membase = (__iomem void *) KSEG1ADDR(EARLY_UART_BASE);
+static __iomem void *chipid_membase = (__iomem void *) KSEG1ADDR(CHIPID_BASE);
+static int init_complete;
+
+static inline void uart_w32(u32 val, unsigned reg)
+{
+	__raw_writel(val, uart_membase + reg);
+}
+
+static inline u32 uart_r32(unsigned reg)
+{
+	return __raw_readl(uart_membase + reg);
+}
+
+static inline int soc_is_mt7628(void)
+{
+	return IS_ENABLED(CONFIG_SOC_MT7620) &&
+		(__raw_readl(chipid_membase) == MT7628_CHIP_NAME1);
+}
+
+static void find_uart_base(void)
+{
+	int i;
+
+	if (!soc_is_mt7628())
+		return;
+
+	for (i = 0; i < 3; i++) {
+		u32 reg = uart_r32(UART_REG_LCR + (0x100 * i));
+
+		if (!reg)
+			continue;
+
+		uart_membase = (__iomem void *) KSEG1ADDR(EARLY_UART_BASE +
+							  (0x100 * i));
+		break;
+	}
+}
+
+void prom_putchar(char ch)
+{
+	if (!init_complete) {
+		find_uart_base();
+		init_complete = 1;
+	}
+
+	if (IS_ENABLED(CONFIG_SOC_MT7621) || soc_is_mt7628()) {
+		uart_w32((unsigned char)ch, UART_TX);
+		while ((uart_r32(UART_REG_LSR) & UART_LSR_THRE) == 0)
+			;
+	} else {
+		while ((uart_r32(UART_REG_LSR_RT2880) & UART_LSR_THRE) == 0)
+			;
+		uart_w32((unsigned char)ch, UART_REG_TX);
+		while ((uart_r32(UART_REG_LSR_RT2880) & UART_LSR_THRE) == 0)
+			;
+	}
+}