rockchip: add early uart driver

add early uart driver so we can print debug message in
SPL stage

Signed-off-by: Lin Huang <hl@rock-chips.com>
Acked-by: Simon Glass <sjg@chromium.org>

arch/arm/include/asm/arch-rockchip/uart.h

+/*
+ * (C) Copyright 2015 Rockchip Electronics Co., Ltd
+ *
+ * SPDX-License-Identifier:     GPL-2.0+
+ */
+
+#ifndef __ASM_ARCH_UART_H
+#define __ASM_ARCH_UART_H
+struct rk_uart {
+	unsigned int rbr; /* Receive buffer register. */
+	unsigned int ier; /* Interrupt enable register. */
+	unsigned int fcr; /* FIFO control register. */
+	unsigned int lcr; /* Line control register. */
+	unsigned int mcr; /* Modem control register. */
+	unsigned int lsr; /* Line status register. */
+	unsigned int msr; /* Modem status register. */
+	unsigned int scr;
+	unsigned int reserved1[(0x30 - 0x20) / 4];
+	unsigned int srbr[(0x70 - 0x30) / 4];
+	unsigned int far;
+	unsigned int tfr;
+	unsigned int rfw;
+	unsigned int usr;
+	unsigned int tfl;
+	unsigned int rfl;
+	unsigned int srr;
+	unsigned int srts;
+	unsigned int sbcr;
+	unsigned int sdmam;
+	unsigned int sfe;
+	unsigned int srt;
+	unsigned int stet;
+	unsigned int htx;
+	unsigned int dmasa;
+	unsigned int reserver2[(0xf4 - 0xac) / 4];
+	unsigned int cpr;
+	unsigned int ucv;
+	unsigned int ctr;
+};
+
+void rk_uart_init(void *base);
+void print_hex(unsigned int n);
+void print(char *s);
+#endif

arch/arm/mach-rockchip/Makefile

@@ -10,5 +10,6 @@ else
 obj-y += board.o
 endif
 obj-y += rk_timer.o
+obj-y += rk_early_print.o
 obj-$(CONFIG_$(SPL_)ROCKCHIP_COMMON) += common.o
 obj-$(CONFIG_ROCKCHIP_RK3288) += rk3288/

arch/arm/mach-rockchip/rk_early_print.c

+/*
+ * (C) Copyright 2015 Rockchip Electronics Co., Ltd
+ *
+ * SPDX-License-Identifier:     GPL-2.0+
+ */
+
+#include <asm/io.h>
+#include <asm/arch/uart.h>
+#include <common.h>
+
+static struct rk_uart *uart_ptr;
+
+static void uart_wrtie_byte(char byte)
+{
+	writel(byte, &uart_ptr->rbr);
+	while (!(readl(&uart_ptr->lsr) & 0x40))
+		;
+}
+
+void print(char *s)
+{
+	while (*s) {
+		if (*s == '\n')
+			uart_wrtie_byte('\r');
+	    uart_wrtie_byte(*s);
+	    s++;
+	}
+}
+
+void print_hex(unsigned int n)
+{
+	int i;
+	int temp;
+
+	uart_wrtie_byte('0');
+	uart_wrtie_byte('x');
+
+	for (i = 8; i > 0; i--) {
+		temp = (n >> (i - 1) * 4) & 0x0f;
+		if (temp < 10)
+			uart_wrtie_byte((char)(temp + '0'));
+		else
+			uart_wrtie_byte((char)(temp - 10 + 'a'));
+	}
+	uart_wrtie_byte('\n');
+	uart_wrtie_byte('\r');
+}
+
+/*
+ * TODO: since rk3036 only 4K sram to use in SPL, for saving space,
+ * we implement uart driver this way, we should convert this to use
+ * ns16550 driver in future, which support DEBUG_UART in the standard way
+ */
+void rk_uart_init(void *base)
+{
+	uart_ptr = (struct rk_uart *)base;
+	writel(0x83, &uart_ptr->lcr);
+	writel(0x0d, &uart_ptr->rbr);
+	writel(0x03, &uart_ptr->lcr);
+
+	/* fifo enable, sfe is shadow register of FCR[0] */
+	writel(0x01, &uart_ptr->sfe);
+}