lib: utils/serial: Add support for Gaisler APBUART

This patch adds support for the UART used by the NOEL-V processor.

Cobham Gaisler's NOEL-V RISC-V processor IP is available under GPL
and commercial license and is described in more detail at
https://www.gaisler.com/noelv.

Signed-off-by: Daniel Cederman <cederman@gaisler.com>
Reviewed-by: Anup Patel <anup.patel@wdc.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

include/sbi_utils/fdt/fdt_helper.h

@@ -39,6 +39,9 @@ int fdt_parse_hart_id(void *fdt, int cpu_offset, u32 *hartid);
 
 int fdt_parse_max_hart_id(void *fdt, u32 *max_hartid);
 
+int fdt_parse_gaisler_uart_node(void *fdt, int nodeoffset,
+				struct platform_uart_data *uart);
+
 int fdt_parse_shakti_uart_node(void *fdt, int nodeoffset,
 			       struct platform_uart_data *uart);
 

include/sbi_utils/serial/gaisler-uart.h

@@ -0,0 +1,17 @@
+/*
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (c) 2021 Cobham Gaisler AB.
+ *
+ * Authors:
+ *   Daniel Cederman <cederman@gaisler.com>
+ */
+
+#ifndef __SERIAL_GAISLER_APBUART_H__
+#define __SERIAL_GAISLER_APBUART_H__
+
+#include <sbi/sbi_types.h>
+
+int gaisler_uart_init(unsigned long base, u32 in_freq, u32 baudrate);
+
+#endif

lib/utils/fdt/fdt_helper.c

@@ -26,6 +26,8 @@
 #define DEFAULT_SIFIVE_UART_REG_SHIFT		0
 #define DEFAULT_SIFIVE_UART_REG_IO_WIDTH	4
 
+#define DEFAULT_GAISLER_UART_REG_IO_WIDTH	4
+
 #define DEFAULT_SHAKTI_UART_FREQ		50000000
 #define DEFAULT_SHAKTI_UART_BAUD		115200
 
@@ -213,6 +215,44 @@ int fdt_parse_max_hart_id(void *fdt, u32 *max_hartid)
 	return 0;
 }
 
+int fdt_parse_gaisler_uart_node(void *fdt, int nodeoffset,
+				struct platform_uart_data *uart)
+{
+	int len, rc;
+	const fdt32_t *val;
+	unsigned long reg_addr, reg_size;
+
+	if (nodeoffset < 0 || !uart || !fdt)
+		return SBI_ENODEV;
+
+	rc = fdt_get_node_addr_size(fdt, nodeoffset, &reg_addr, &reg_size);
+	if (rc < 0 || !reg_addr || !reg_size)
+		return SBI_ENODEV;
+	uart->addr = reg_addr;
+
+	/**
+	 * UART address is mandatory. clock-frequency and current-speed
+	 * may not be present. Don't return error.
+	 */
+	val = (fdt32_t *)fdt_getprop(fdt, nodeoffset, "clock-frequency", &len);
+	if (len > 0 && val)
+		uart->freq = fdt32_to_cpu(*val);
+	else
+		uart->freq = DEFAULT_UART_FREQ;
+
+	val = (fdt32_t *)fdt_getprop(fdt, nodeoffset, "current-speed", &len);
+	if (len > 0 && val)
+		uart->baud = fdt32_to_cpu(*val);
+	else
+		uart->baud = DEFAULT_UART_BAUD;
+
+	/* For Gaisler APBUART, the reg-shift and reg-io-width are fixed .*/
+	uart->reg_shift	   = DEFAULT_UART_REG_SHIFT;
+	uart->reg_io_width = DEFAULT_GAISLER_UART_REG_IO_WIDTH;
+
+	return 0;
+}
+
 int fdt_parse_shakti_uart_node(void *fdt, int nodeoffset,
 			       struct platform_uart_data *uart)
 {

lib/utils/serial/fdt_serial.c

@@ -16,12 +16,14 @@ extern struct fdt_serial fdt_serial_uart8250;
 extern struct fdt_serial fdt_serial_sifive;
 extern struct fdt_serial fdt_serial_htif;
 extern struct fdt_serial fdt_serial_shakti;
+extern struct fdt_serial fdt_serial_gaisler;
 
 static struct fdt_serial *serial_drivers[] = {
 	&fdt_serial_uart8250,
 	&fdt_serial_sifive,
 	&fdt_serial_htif,
 	&fdt_serial_shakti,
+	&fdt_serial_gaisler
 };
 
 static struct fdt_serial dummy = {

lib/utils/serial/fdt_serial_gaisler.c

@@ -0,0 +1,35 @@
+/*
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (c) 2021 Cobham Gaisler AB.
+ *
+ * Authors:
+ *   Daniel Cederman <cederman@gaisler.com>
+ */
+
+#include <sbi_utils/fdt/fdt_helper.h>
+#include <sbi_utils/serial/fdt_serial.h>
+#include <sbi_utils/serial/gaisler-uart.h>
+
+static int serial_gaisler_init(void *fdt, int nodeoff,
+			       const struct fdt_match *match)
+{
+	int rc;
+	struct platform_uart_data uart;
+
+	rc = fdt_parse_gaisler_uart_node(fdt, nodeoff, &uart);
+	if (rc)
+		return rc;
+
+	return gaisler_uart_init(uart.addr, uart.freq, uart.baud);
+}
+
+static const struct fdt_match serial_gaisler_match[] = {
+	{ .compatible = "gaisler,apbuart" },
+	{},
+};
+
+struct fdt_serial fdt_serial_gaisler = {
+	.match_table = serial_gaisler_match,
+	.init = serial_gaisler_init
+};

lib/utils/serial/gaisler-uart.c

@@ -0,0 +1,86 @@
+/*
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (c) 2021 Cobham Gaisler AB.
+ *
+ * Authors:
+ *   Daniel Cederman <cederman@gaisler.com>
+ */
+
+#include <sbi/riscv_io.h>
+#include <sbi/sbi_console.h>
+#include <sbi_utils/serial/gaisler-uart.h>
+
+/* clang-format off */
+
+#define UART_REG_DATA		0
+#define UART_REG_STATUS		1
+#define UART_REG_CTRL		2
+#define UART_REG_SCALER		3
+
+#define UART_DATA_DATA		0x000000ff
+#define UART_STATUS_FIFOFULL	0x00000200
+#define UART_STATUS_DATAREADY	0x00000001
+
+#define UART_CTRL_DB		(1<<11)
+#define UART_CTRL_FL		(1<<6)
+#define UART_CTRL_TE		(1<<1)
+#define UART_CTRL_RE		(1<<0)
+
+/* clang-format on */
+
+static volatile void *uart_base;
+
+static u32 get_reg(u32 num)
+{
+	return readl(uart_base + (num * 0x4));
+}
+
+static void set_reg(u32 num, u32 val)
+{
+	writel(val, uart_base + (num * 0x4));
+}
+
+static void gaisler_uart_putc(char ch)
+{
+	while (get_reg(UART_REG_STATUS) & UART_STATUS_FIFOFULL)
+		;
+
+	set_reg(UART_REG_DATA, ch);
+}
+
+static int gaisler_uart_getc(void)
+{
+	u32 ret = get_reg(UART_REG_STATUS);
+	if (!(ret & UART_STATUS_DATAREADY))
+		return -1;
+	return get_reg(UART_REG_DATA) & UART_DATA_DATA;
+}
+
+static struct sbi_console_device gaisler_console = {
+	.name	      = "gaisler_uart",
+	.console_putc = gaisler_uart_putc,
+	.console_getc = gaisler_uart_getc
+};
+
+int gaisler_uart_init(unsigned long base, u32 in_freq, u32 baudrate)
+{
+	u32 ctrl;
+
+	uart_base = (volatile void *)base;
+
+	/* Configure baudrate */
+	if (in_freq)
+		set_reg(UART_REG_SCALER, in_freq / (baudrate * 8 + 7));
+
+	ctrl = get_reg(UART_REG_CTRL);
+	/* Preserve debug mode and flow control */
+	ctrl &= (UART_CTRL_DB | UART_CTRL_FL);
+	/* Enable TX and RX */
+	ctrl |= UART_CTRL_TE | UART_CTRL_RE;
+	set_reg(UART_REG_CTRL, ctrl);
+
+	sbi_console_set_device(&gaisler_console);
+
+	return 0;
+}

lib/utils/serial/objects.mk

@@ -8,10 +8,12 @@
 #
 
 libsbiutils-objs-y += serial/fdt_serial.o
+libsbiutils-objs-y += serial/fdt_serial_gaisler.o
 libsbiutils-objs-y += serial/fdt_serial_htif.o
 libsbiutils-objs-y += serial/fdt_serial_shakti.o
 libsbiutils-objs-y += serial/fdt_serial_sifive.o
 libsbiutils-objs-y += serial/fdt_serial_uart8250.o
+libsbiutils-objs-y += serial/gaisler-uart.o
 libsbiutils-objs-y += serial/shakti-uart.o
 libsbiutils-objs-y += serial/sifive-uart.o
 libsbiutils-objs-y += serial/uart8250.o