[PATCH v4] lib: utils: Add LiteX UART support
Anup Patel
anup at brainfault.org
Tue Nov 16 08:08:40 PST 2021
On Mon, Nov 15, 2021 at 11:51 PM Gabriel Somlo <gsomlo at gmail.com> wrote:
>
> 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;
> +}
> +
You can drop fdt_parse_litex_uart_node() and directly use
fdt_get_node_addr_size() in serial_litex_init() below.
> 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
>
>
> --
> opensbi mailing list
> opensbi at lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/opensbi
Apart from the comment on fdt_parse_litex_uart_node(), this
looks good to me.
Reviewed-by: Anup Patel <anup.patel at wdc.com>
Regards,
Anup
More information about the opensbi
mailing list