[PATCH v4] lib: utils: Add LiteX UART support
Gabriel L. Somlo
gsomlo at gmail.com
Tue Nov 16 08:41:07 PST 2021
Hi Anup,
On Tue, Nov 16, 2021 at 09:38:40PM +0530, Anup Patel wrote:
> 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.
Makes sense, will do.
> > 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
> >
>
> Apart from the comment on fdt_parse_litex_uart_node(), this
> looks good to me.
>
> Reviewed-by: Anup Patel <anup.patel at wdc.com>
Thanks! I've made the change you suggested, and will send out v5
later this evening (once I've had a chance to actually run it on
actual hardware -- out of an "abundance of caution"... :)
Best,
--Gabriel
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