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-rw-r--r--src/drivers/uart/Kconfig5
-rw-r--r--src/drivers/uart/Makefile.inc7
-rw-r--r--src/drivers/uart/sifive.c114
3 files changed, 126 insertions, 0 deletions
diff --git a/src/drivers/uart/Kconfig b/src/drivers/uart/Kconfig
index 54f591d9ad..bfc5ccee61 100644
--- a/src/drivers/uart/Kconfig
+++ b/src/drivers/uart/Kconfig
@@ -61,6 +61,11 @@ config DRIVERS_UART_PL011
default n
select HAVE_UART_SPECIAL
+config DRIVERS_UART_SIFIVE
+ bool
+ select HAVE_UART_SPECIAL
+ select UART_OVERRIDE_INPUT_CLOCK_DIVIDER
+
config UART_USE_REFCLK_AS_INPUT_CLOCK
bool
default n
diff --git a/src/drivers/uart/Makefile.inc b/src/drivers/uart/Makefile.inc
index ebaa5d4a0b..c7aa1ae784 100644
--- a/src/drivers/uart/Makefile.inc
+++ b/src/drivers/uart/Makefile.inc
@@ -42,4 +42,11 @@ ramstage-y += pl011.c
verstage-y += pl011.c
endif
+ifeq ($(CONFIG_DRIVERS_UART_SIFIVE),y)
+bootblock-$(CONFIG_BOOTBLOCK_CONSOLE) += sifive.c
+romstage-y += sifive.c
+postcar-y += sifive.c
+ramstage-y += sifive.c
+endif
+
endif
diff --git a/src/drivers/uart/sifive.c b/src/drivers/uart/sifive.c
new file mode 100644
index 0000000000..dd47cafcf1
--- /dev/null
+++ b/src/drivers/uart/sifive.c
@@ -0,0 +1,114 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * Copyright (C) 2018 Jonathan Neuschäfer
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ */
+
+#include <arch/io.h>
+#include <boot/coreboot_tables.h>
+#include <console/uart.h>
+#include <types.h>
+
+/*
+ * This is a driver for SiFive's own UART, documented in the FU540 manual:
+ * https://www.sifive.com/documentation/chips/freedom-u540-c000-manual/
+ */
+
+struct sifive_uart_registers {
+ uint32_t txdata; /* Transmit data register */
+ uint32_t rxdata; /* Receive data register */
+ uint32_t txctrl; /* Transmit control register */
+ uint32_t rxctrl; /* Receive control register */
+ uint32_t ie; /* UART interrupt enable */
+ uint32_t ip; /* UART interrupt pending */
+ uint32_t div; /* Baud rate divisor */
+} __packed;
+
+#define TXDATA_FULL BIT(31)
+#define RXDATA_EMPTY BIT(31)
+#define TXCTRL_TXEN BIT(0)
+#define TXCTRL_NSTOP_SHIFT 1
+#define TXCTRL_NSTOP(x) (((x)-1) << TXCTRL_NSTOP_SHIFT)
+#define TXCTRL_TXCNT_SHIFT 16
+#define TXCTRL_TXCNT(x) ((x) << TXCTRL_TXCNT_SHIFT)
+#define RXCTRL_RXEN BIT(0)
+#define RXCTRL_RXCNT_SHIFT 16
+#define RXCTRL_RXCNT(x) ((x) << RXCTRL_RXCNT_SHIFT)
+#define IP_TXWM BIT(0)
+#define IP_RXWM BIT(1)
+
+void uart_init(int idx)
+{
+ struct sifive_uart_registers *regs = uart_platform_baseptr(idx);
+
+ /* TODO: Configure the divisor */
+
+ /* Enable transmission, one stop bit, transmit watermark at 1 */
+ write32(&regs->txctrl, TXCTRL_TXEN|TXCTRL_NSTOP(1)|TXCTRL_TXCNT(1));
+
+ /* Enable reception, receive watermark at 0 */
+ write32(&regs->rxctrl, RXCTRL_RXEN|RXCTRL_RXCNT(0));
+}
+
+static bool uart_can_tx(struct sifive_uart_registers *regs)
+{
+ return !(read32(&regs->txdata) & TXDATA_FULL);
+}
+
+void uart_tx_byte(int idx, unsigned char data)
+{
+ struct sifive_uart_registers *regs = uart_platform_baseptr(idx);
+
+ while (!uart_can_tx(regs))
+ ; /* TODO: implement a timeout */
+
+ write32(&regs->txdata, data);
+}
+
+void uart_tx_flush(int idx)
+{
+ struct sifive_uart_registers *regs = uart_platform_baseptr(idx);
+ uint32_t ip;
+
+ /* Use the TX watermark bit to find out if the TX FIFO is empty */
+ do {
+ ip = read32(&regs->ip);
+ } while (!(ip & IP_TXWM));
+}
+
+unsigned char uart_rx_byte(int idx)
+{
+ struct sifive_uart_registers *regs = uart_platform_baseptr(idx);
+ uint32_t rxdata;
+
+ do {
+ rxdata = read32(&regs->rxdata);
+ } while (rxdata & RXDATA_EMPTY);
+
+ return rxdata & 0xff;
+}
+
+unsigned int uart_input_clock_divider(void)
+{
+ /*
+ * The SiFive UART handles oversampling internally. The divided clock
+ * is the baud clock.
+ */
+ return 1;
+}
+
+#ifndef __PRE_RAM__
+void uart_fill_lb(void *data)
+{
+ /* TODO */
+}
+#endif