[PATCH v1] lib: utils: Add LiteX UART support
Gabriel Somlo
gsomlo at gmail.com
Wed Nov 10 15:04:59 PST 2021
The LiteX SoC framework (https://github.com/enjoy-digital/litex)
provides a wide range of building blocks that allow creation of
full FPGA based systems. CPU options supported by LiteX span
several RISC-V models, including Rocket (64-bit) and VexRiscv
(32-bit).
This patch adds support for detecting and provisioning LiteX's
UART based on its FDT info (detailed in the Linux sources at
Documentation/devicetree/bindings/serial/litex,liteuart.yaml).
Signed-off-by: Gabriel Somlo <gsomlo at gmail.com>
---
See https://github.com/litex-hub/linux-on-litex-rocket for instructions
on how to build a LiteX+Rocket bitstream for e.g. the nexys4ddr (Xilinx
Artix7 FPGA dev board), and https://pastebin.com/nu1dSE16 for a demo of
the board booting a linux payload via opensbi, using this patch.
Thanks for your consideration,
--Gabriel
include/sbi_utils/fdt/fdt_helper.h | 3 ++
include/sbi_utils/serial/litex-uart.h | 17 +++++++
lib/utils/fdt/fdt_helper.c | 28 ++++++++++++
lib/utils/serial/fdt_serial.c | 2 +
lib/utils/serial/fdt_serial_litex.c | 35 +++++++++++++++
lib/utils/serial/litex-uart.c | 64 +++++++++++++++++++++++++++
lib/utils/serial/objects.mk | 2 +
7 files changed, 151 insertions(+)
create mode 100644 include/sbi_utils/serial/litex-uart.h
create mode 100644 lib/utils/serial/fdt_serial_litex.c
create mode 100644 lib/utils/serial/litex-uart.c
diff --git a/include/sbi_utils/fdt/fdt_helper.h b/include/sbi_utils/fdt/fdt_helper.h
index 24fee7a..5f75f07 100644
--- a/include/sbi_utils/fdt/fdt_helper.h
+++ b/include/sbi_utils/fdt/fdt_helper.h
@@ -62,6 +62,9 @@ int fdt_parse_shakti_uart_node(void *fdt, int nodeoffset,
int fdt_parse_sifive_uart_node(void *fdt, int nodeoffset,
struct platform_uart_data *uart);
+int fdt_parse_litex_uart_node(void *fdt, int nodeoffset,
+ struct platform_uart_data *uart);
+
int fdt_parse_uart8250_node(void *fdt, int nodeoffset,
struct platform_uart_data *uart);
diff --git a/include/sbi_utils/serial/litex-uart.h b/include/sbi_utils/serial/litex-uart.h
new file mode 100644
index 0000000..002b525
--- /dev/null
+++ b/include/sbi_utils/serial/litex-uart.h
@@ -0,0 +1,17 @@
+/*
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (c) 2021 Gabriel Somlo
+ *
+ * Authors:
+ * Gabriel Somlo <gsomlo at gmail.com>
+ */
+
+#ifndef __SERIAL_LITEX_UART_H__
+#define __SERIAL_LITEX_UART_H__
+
+#include <sbi/sbi_types.h>
+
+int litex_uart_init(unsigned long base, u32 in_freq, u32 baudrate);
+
+#endif
diff --git a/lib/utils/fdt/fdt_helper.c b/lib/utils/fdt/fdt_helper.c
index 5bf4021..3ba78e5 100644
--- a/lib/utils/fdt/fdt_helper.c
+++ b/lib/utils/fdt/fdt_helper.c
@@ -25,6 +25,11 @@
#define DEFAULT_SIFIVE_UART_REG_SHIFT 0
#define DEFAULT_SIFIVE_UART_REG_IO_WIDTH 4
+#define DEFAULT_LITEX_UART_FREQ 0
+#define DEFAULT_LITEX_UART_BAUD 115200
+#define DEFAULT_LITEX_UART_REG_SHIFT 0
+#define DEFAULT_LITEX_UART_REG_IO_WIDTH 4
+
#define DEFAULT_GAISLER_UART_REG_IO_WIDTH 4
#define DEFAULT_SHAKTI_UART_FREQ 50000000
@@ -403,6 +408,29 @@ int fdt_parse_sifive_uart_node(void *fdt, int nodeoffset,
return 0;
}
+int fdt_parse_litex_uart_node(void *fdt, int nodeoffset,
+ struct platform_uart_data *uart)
+{
+ int rc;
+ uint64_t reg_addr, reg_size;
+
+ if (nodeoffset < 0 || !uart || !fdt)
+ return SBI_ENODEV;
+
+ rc = fdt_get_node_addr_size(fdt, nodeoffset, 0, ®_addr, ®_size);
+ if (rc < 0 || !reg_addr || !reg_size)
+ return SBI_ENODEV;
+ uart->addr = reg_addr;
+
+ /* For LiteX UART, the following properties are ignored */
+ uart->freq = DEFAULT_LITEX_UART_FREQ;
+ uart->baud = DEFAULT_LITEX_UART_BAUD;
+ uart->reg_shift = DEFAULT_LITEX_UART_REG_SHIFT;
+ uart->reg_io_width = DEFAULT_LITEX_UART_REG_IO_WIDTH;
+
+ return 0;
+}
+
int fdt_parse_uart8250_node(void *fdt, int nodeoffset,
struct platform_uart_data *uart)
{
diff --git a/lib/utils/serial/fdt_serial.c b/lib/utils/serial/fdt_serial.c
index cedda04..f73d26a 100644
--- a/lib/utils/serial/fdt_serial.c
+++ b/lib/utils/serial/fdt_serial.c
@@ -15,6 +15,7 @@
extern struct fdt_serial fdt_serial_uart8250;
extern struct fdt_serial fdt_serial_sifive;
+extern struct fdt_serial fdt_serial_litex;
extern struct fdt_serial fdt_serial_htif;
extern struct fdt_serial fdt_serial_shakti;
extern struct fdt_serial fdt_serial_gaisler;
@@ -22,6 +23,7 @@ extern struct fdt_serial fdt_serial_gaisler;
static struct fdt_serial *serial_drivers[] = {
&fdt_serial_uart8250,
&fdt_serial_sifive,
+ &fdt_serial_litex,
&fdt_serial_htif,
&fdt_serial_shakti,
&fdt_serial_gaisler
diff --git a/lib/utils/serial/fdt_serial_litex.c b/lib/utils/serial/fdt_serial_litex.c
new file mode 100644
index 0000000..fda5746
--- /dev/null
+++ b/lib/utils/serial/fdt_serial_litex.c
@@ -0,0 +1,35 @@
+/*
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (c) 2021 Gabriel Somlo
+ *
+ * Authors:
+ * Gabriel Somlo <gsomlo at gmail.com>
+ */
+
+#include <sbi_utils/fdt/fdt_helper.h>
+#include <sbi_utils/serial/fdt_serial.h>
+#include <sbi_utils/serial/litex-uart.h>
+
+static int serial_litex_init(void *fdt, int nodeoff,
+ const struct fdt_match *match)
+{
+ int rc;
+ struct platform_uart_data uart;
+
+ rc = fdt_parse_litex_uart_node(fdt, nodeoff, &uart);
+ if (rc)
+ return rc;
+
+ return litex_uart_init(uart.addr, uart.freq, uart.baud);
+}
+
+static const struct fdt_match serial_litex_match[] = {
+ { .compatible = "litex,liteuart" },
+ { },
+};
+
+struct fdt_serial fdt_serial_litex = {
+ .match_table = serial_litex_match,
+ .init = serial_litex_init
+};
diff --git a/lib/utils/serial/litex-uart.c b/lib/utils/serial/litex-uart.c
new file mode 100644
index 0000000..e6afa53
--- /dev/null
+++ b/lib/utils/serial/litex-uart.c
@@ -0,0 +1,64 @@
+/*
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (c) 2021 Gabriel Somlo
+ *
+ * Authors:
+ * Gabriel Somlo <gsomlo at gmail.com>
+ */
+
+#include <sbi/riscv_io.h>
+#include <sbi/sbi_console.h>
+#include <sbi_utils/serial/litex-uart.h>
+
+/* clang-format off */
+
+#define UART_REG_RXTX 0
+#define UART_REG_TXFULL 1
+#define UART_REG_RXEMPTY 2
+#define UART_REG_EV_STATUS 3
+#define UART_REG_EV_PENDING 4
+#define UART_REG_EV_ENABLE 5
+
+/* 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 litex_uart_putc(char ch)
+{
+ while ((get_reg(UART_REG_TXFULL) & 0x01));
+ set_reg(UART_REG_RXTX, ch);
+}
+
+static int litex_uart_getc(void)
+{
+ int ret = -1;
+ if (!(get_reg(UART_REG_RXEMPTY) & 0x01)) {
+ ret = get_reg(UART_REG_RXTX);
+ set_reg(UART_REG_EV_PENDING, 0x02); /* ack UART_EV_RX */
+ }
+ return ret;
+}
+
+static struct sbi_console_device litex_console = {
+ .name = "litex_uart",
+ .console_putc = litex_uart_putc,
+ .console_getc = litex_uart_getc
+};
+
+int litex_uart_init(unsigned long base, u32 in_freq, u32 baudrate)
+{
+ uart_base = (volatile void *)base;
+ sbi_console_set_device(&litex_console);
+ return 0;
+}
diff --git a/lib/utils/serial/objects.mk b/lib/utils/serial/objects.mk
index 9fb0902..4f751ba 100644
--- a/lib/utils/serial/objects.mk
+++ b/lib/utils/serial/objects.mk
@@ -12,8 +12,10 @@ 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_litex.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/litex-uart.o
libsbiutils-objs-y += serial/uart8250.o
--
2.31.1
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