[PATCH v4] lib: utils: Add LiteX UART support
Gabriel Somlo
gsomlo at gmail.com
Mon Nov 15 10:20:43 PST 2021
Add support for the UART provided by the LiteX SoC
framework (https://github.com/enjoy-digital/litex),
based on its FDT info (described in the Linux tree at
Documentation/devicetree/bindings/serial/litex,liteuart.yaml).
Signed-off-by: Gabriel Somlo <gsomlo at gmail.com>
---
New in v4:
- fix typo(s) in commit blurb
- explicitly disable IRQs during Litex UART initialization
>New in v3:
> - less verbose / more concise commit blurb :)
> - fixed serial_litex_init() alignment
> - fixed `uart_base` pointer arithmetic
> - treat single-bit registers as Boolean
> - removed access to `event` (irq-related) register
> (not needed since UART is operated in polling mode)
>
>> New in v2:
>> - remove properties (and parameters) not actually used by the
>> LiteX UART
>> - remove redundant parentheses from pointer arithmetic
>> (thanks jrtc27!)
>>
>>> 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.
include/sbi_utils/fdt/fdt_helper.h | 3 ++
include/sbi_utils/serial/litex-uart.h | 17 ++++++++
lib/utils/fdt/fdt_helper.c | 19 ++++++++
lib/utils/serial/fdt_serial.c | 2 +
lib/utils/serial/fdt_serial_litex.c | 35 +++++++++++++++
lib/utils/serial/litex-uart.c | 63 +++++++++++++++++++++++++++
lib/utils/serial/objects.mk | 2 +
7 files changed, 141 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..91ab644
--- /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);
+
+#endif
diff --git a/lib/utils/fdt/fdt_helper.c b/lib/utils/fdt/fdt_helper.c
index 5bf4021..a42f53b 100644
--- a/lib/utils/fdt/fdt_helper.c
+++ b/lib/utils/fdt/fdt_helper.c
@@ -403,6 +403,25 @@ 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;
+
+ /* LiteX UART has no further configurable properties */
+
+ 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..0fa5777
--- /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);
+}
+
+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..f843bf3
--- /dev/null
+++ b/lib/utils/serial/litex-uart.c
@@ -0,0 +1,63 @@
+/*
+ * 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 u32 *uart_base;
+
+static u8 get_reg(u8 reg)
+{
+ return readb(uart_base + reg);
+}
+
+static void set_reg(u8 reg, u8 val)
+{
+ writeb(val, uart_base + reg);
+}
+
+static void litex_uart_putc(char ch)
+{
+ while (get_reg(UART_REG_TXFULL));
+ set_reg(UART_REG_RXTX, ch);
+}
+
+static int litex_uart_getc(void)
+{
+ if (get_reg(UART_REG_RXEMPTY))
+ return -1;
+ else
+ return get_reg(UART_REG_RXTX);
+}
+
+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)
+{
+ uart_base = (volatile u32 *)base;
+ set_reg(UART_REG_EV_ENABLE, 0); /* UART in polling mode: disable IRQ */
+ 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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