lib: utils: serial: Add Renesas SCIF driver

Add Renesas SCIF driver.

Based on a patch in the BSP by Takeki Hamada
<takeki.hamada.ak@bp.renesas.com>
Link: https://github.com/renesas-rz/rz_opensbi/commits/work/OpenSBI-PMA

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Anup Patel <anup@brainfault.org>

lib/utils/serial/Kconfig

@@ -59,6 +59,10 @@ config SERIAL_GAISLER
 	bool "Gaisler UART support"
 	default n
 
+config SERIAL_RENESAS_SCIF
+	bool "Renesas SCIF support"
+	default n
+
 config SERIAL_SHAKTI
 	bool "Shakti UART support"
 	default n

lib/utils/serial/objects.mk

@@ -36,6 +36,7 @@ libsbiutils-objs-$(CONFIG_FDT_SERIAL_XILINX_UARTLITE) += serial/fdt_serial_xlnx_
 
 libsbiutils-objs-$(CONFIG_SERIAL_CADENCE) += serial/cadence-uart.o
 libsbiutils-objs-$(CONFIG_SERIAL_GAISLER) += serial/gaisler-uart.o
+libsbiutils-objs-$(CONFIG_SERIAL_RENESAS_SCIF) += serial/renesas_scif.o
 libsbiutils-objs-$(CONFIG_SERIAL_SHAKTI) += serial/shakti-uart.o
 libsbiutils-objs-$(CONFIG_SERIAL_SIFIVE) += serial/sifive-uart.o
 libsbiutils-objs-$(CONFIG_SERIAL_LITEX) += serial/litex-uart.o

lib/utils/serial/renesas_scif.c

@@ -0,0 +1,116 @@
+// SPDX-License-Identifier: BSD-2-Clause
+/*
+ * Copyright (C) 2022 Renesas Electronics Corporation
+ */
+
+#include <sbi/riscv_io.h>
+#include <sbi/sbi_console.h>
+#include <sbi/sbi_timer.h>
+#include <sbi_utils/serial/renesas-scif.h>
+
+/* clang-format off */
+
+#define SCIF_REG_SMR		0x0
+#define SCIF_REG_BRR		0x2
+#define SCIF_REG_SCR		0x4
+#define SCIF_REG_FTDR		0x6
+#define SCIF_REG_FSR		0x8
+#define SCIF_REG_FCR		0xc
+#define SCIF_REG_LSR		0x12
+#define SCIF_REG_SEMR		0x14
+
+#define SCIF_FCR_RFRST		0x2 /* Reset assert receive-FIFO (bit[1]) */
+#define SCIF_FCR_TFRST		0x4 /* Reset assert transmit-FIFO(bit[2]) */
+
+#define SCIF_FCR_RST_ASSRT_RFTF	(SCIF_FCR_RFRST | SCIF_FCR_TFRST) /* Reset assert tx-FIFO & rx-FIFO */
+#define SCIF_FCR_RST_NGATE_RFTF	0x0 /* Reset negate tx-FIFO & rx-FIFO */
+
+#define SCIF_SCR_RE		0x10 /* Enable receive (bit[4]) */
+#define SCIF_SCR_TE		0x20 /* Enable transmit(bit[5]) */
+#define SCIF_SCR_RCV_TRN_EN	(SCIF_SCR_RE | SCIF_SCR_TE) /* Enable receive & transmit */
+#define SCIF_SCR_RCV_TRN_DIS	0x0 /* Disable receive & transmit */
+
+#define SCIF_FSR_ER		0x80 /* Receive error flag */
+#define SCIF_FSR_TEND		0x40 /* Transmit End Flag */
+#define SCIF_FSR_TDFE		0x20 /* Transmit FIFO Data Empty Flag */
+#define SCIF_FSR_BRK		0x10 /* Detect break flag */
+#define SCIF_FSR_DR		0x1  /* Receive data ready flag */
+
+#define SCIF_FSR_TXD_CHK	(SCIF_FSR_TEND | SCIF_FSR_TDFE)
+
+#define SCIF_SEMR_MDDRS		0x10 /* MDDR access enable */
+
+#define SCIF_REG_8BIT(reg)	((reg == SCIF_REG_BRR) || \
+				 (reg == SCIF_REG_FTDR) || \
+				 (reg == SCIF_REG_SEMR))
+
+#define SCBRR_VALUE(clk, baudrate) ((clk) / (32 * (baudrate)) - 1)
+
+/* clang-format on */
+
+static volatile char *scif_base;
+
+static u32 get_reg(u32 offset)
+{
+	if (SCIF_REG_8BIT(offset))
+		return readb(scif_base + offset);
+
+	return readw(scif_base + offset);
+}
+
+static void set_reg(u32 offset, u32 val)
+{
+	if (SCIF_REG_8BIT(offset))
+		writeb(val, scif_base + offset);
+	else
+		writew(val, scif_base + offset);
+}
+
+static void renesas_scif_putc(char ch)
+{
+	uint16_t reg;
+
+	while (!(SCIF_FSR_TXD_CHK & get_reg(SCIF_REG_FSR)))
+		;
+
+	set_reg(SCIF_REG_FTDR, ch);
+	reg = get_reg(SCIF_REG_FSR);
+	reg &= ~SCIF_FSR_TXD_CHK;
+	set_reg(SCIF_REG_FSR, reg);
+}
+
+static struct sbi_console_device renesas_scif_console = {
+	.name		= "renesas_scif",
+	.console_putc	= renesas_scif_putc,
+};
+
+int renesas_scif_init(unsigned long base, u32 in_freq, u32 baudrate)
+{
+	uint16_t data16;
+
+	scif_base = (volatile char *)base;
+
+	set_reg(SCIF_REG_SCR, SCIF_SCR_RCV_TRN_DIS);
+	set_reg(SCIF_REG_FCR, SCIF_FCR_RST_ASSRT_RFTF);
+
+	data16 = get_reg(SCIF_REG_FSR); /* Dummy read */
+	set_reg(SCIF_REG_FSR, 0x0); /* Clear all error bit */
+
+	data16 = get_reg(SCIF_REG_LSR); /* Dummy read */
+	set_reg(SCIF_REG_LSR, 0x0); /* Clear ORER bit */
+
+	set_reg(SCIF_REG_SCR, 0x0);
+
+	set_reg(SCIF_REG_SMR, 0x0);
+
+	data16 = get_reg(SCIF_REG_SEMR);
+	set_reg(SCIF_REG_SEMR, data16 & (~SCIF_SEMR_MDDRS));
+	set_reg(SCIF_REG_BRR, SCBRR_VALUE(in_freq, baudrate));
+
+	set_reg(SCIF_REG_FCR, SCIF_FCR_RST_NGATE_RFTF);
+	set_reg(SCIF_REG_SCR, SCIF_SCR_RCV_TRN_EN);
+
+	sbi_console_set_device(&renesas_scif_console);
+
+	return 0;
+}