Fwd: [PATCH] serial: implement riscv SBI console support

[Antony Pavlov]

On Fri, 24 Sep 2021 10:13:38 -0300
Marcelo Politzer <marcelo.politzer at cartesi.io> wrote:

Hi, Marcelo!


> Implement a console over legacy SBI (version 0.1.0). There is a tiny ringbuffer
> to simplify checking for presence and reading characters as separate steps.
> 
> Signed-off-by: Marcelo Politzer <marcelo.politzer at cartesi.io>
> ---
>  arch/riscv/cpu/core.c       | 13 ++++++++
>  arch/riscv/lib/sbi.c        | 11 +++++++
>  drivers/serial/Kconfig      |  8 +++++
>  drivers/serial/Makefile     |  1 +
>  drivers/serial/serial_sbi.c | 60 +++++++++++++++++++++++++++++++++++++
>  5 files changed, 93 insertions(+)
>  create mode 100644 drivers/serial/serial_sbi.c
> 
> diff --git a/arch/riscv/cpu/core.c b/arch/riscv/cpu/core.c
> index 80730c05b..9226037f3 100644
> --- a/arch/riscv/cpu/core.c
> +++ b/arch/riscv/cpu/core.c
> @@ -24,6 +24,7 @@
>  #include <magicvar.h>
>  #include <asm/system.h>
>  #include <io.h>
> +#include <asm/sbi.h>

There is no need to include <asm/sbi.h> here.

> 
>  static int riscv_request_stack(void)
>  {
> @@ -33,6 +34,7 @@ static int riscv_request_stack(void)
>  coredevice_initcall(riscv_request_stack);
> 
>  static struct device_d timer_dev;
> +static struct device_d serial_sbi_dev;
> 
>  static s64 hartid;
> 
> @@ -75,6 +77,17 @@ static int riscv_probe(struct device_d *parent)
>                         return ret;
>         }
> 
> +       if (IS_ENABLED(CONFIG_SERIAL_SBI) && !serial_sbi_dev.parent) {
> +               serial_sbi_dev.id = DEVICE_ID_SINGLE;
> +               serial_sbi_dev.device_node = 0;
> +               serial_sbi_dev.parent = parent;
> +               dev_set_name(&serial_sbi_dev, "riscv-serial-sbi");
> +
> +               ret = platform_device_register(&serial_sbi_dev);
> +               if (ret)
> +                       return ret;
> +       }
> +

Please, use tabs for indentation!


>         hartid = riscv_hartid();
>         if (hartid >= 0)
>                 globalvar_add_simple_uint64("hartid", &hartid, "%llu");
> diff --git a/arch/riscv/lib/sbi.c b/arch/riscv/lib/sbi.c
> index 45a04fb82..209069c98 100644
> --- a/arch/riscv/lib/sbi.c
> +++ b/arch/riscv/lib/sbi.c
> @@ -64,3 +64,14 @@ static int sbi_init(void)
> 
>  }
>  core_initcall(sbi_init);
> +
> +

No extra emptyline here.

> +void sbi_console_putchar(int ch)
> +{
> +       sbi_ecall(SBI_EXT_0_1_CONSOLE_PUTCHAR, 0, ch, 0, 0, 0, 0, 0);
> +}
> +
> +int sbi_console_getchar(void)
> +{
> +       return sbi_ecall(SBI_EXT_0_1_CONSOLE_GETCHAR, 0, 0, 0, 0, 0,
> 0, 0).error;
> +}
> diff --git a/drivers/serial/Kconfig b/drivers/serial/Kconfig
> index b9750d177..5e30ea388 100644
> --- a/drivers/serial/Kconfig
> +++ b/drivers/serial/Kconfig
> @@ -173,4 +173,12 @@ config SERIAL_SIFIVE
>           contains a SiFive UART IP block.  This type of UART is present on
>           SiFive FU540 SoCs, among others.
> 
> +config SERIAL_SBI
> +       tristate "RISCV Serial support over SBI's HTIF"
> +       depends on OFDEVICE
> +       depends on RISCV_SBI
> +       help
> +         Select this option if you are building barebox for a RISCV platform
> +         that implements a serial over SBI.
> +
>  endmenu
> diff --git a/drivers/serial/Makefile b/drivers/serial/Makefile
> index 5120b1737..b1de436ed 100644
> --- a/drivers/serial/Makefile
> +++ b/drivers/serial/Makefile
> @@ -24,3 +24,4 @@ obj-$(CONFIG_DRIVER_SERIAL_DIGIC)             +=
> serial_digic.o
>  obj-$(CONFIG_DRIVER_SERIAL_LPUART)             += serial_lpuart.o
>  obj-$(CONFIG_VIRTIO_CONSOLE)                   += virtio_console.o
>  obj-$(CONFIG_SERIAL_SIFIVE)                    += serial_sifive.o
> +obj-$(CONFIG_SERIAL_SBI)                       += serial_sbi.o
> diff --git a/drivers/serial/serial_sbi.c b/drivers/serial/serial_sbi.c
> new file mode 100644
> index 000000000..7217ce9cc
> --- /dev/null
> +++ b/drivers/serial/serial_sbi.c
> @@ -0,0 +1,60 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * Copyright (C) 2021 Marcelo Politzer <marcelo.politzer at cartesi.io>
> + */
> +
> +#include <common.h>
> +#include <driver.h>
> +#include <malloc.h>
> +#include <io.h>
> +#include <of.h>

Please drop <io.h> and <of.h> inclusion here. These header files are unused.

> +#include <asm/sbi.h>
> +
> +struct sbi_serial_priv {
> +       struct console_device cdev;
> +       uint8_t b[2], head, tail;
> +};
> +
> +static int sbi_serial_getc(struct console_device *cdev)
> +{
> +       struct sbi_serial_priv *priv = cdev->dev->priv;
> +       if (priv->head == priv->tail)
> +               return -1;
> +       return priv->b[priv->head++ & 0x1];
> +}
> +
> +static void sbi_serial_putc(struct console_device *cdev, const char ch)
> +{
> +       sbi_console_putchar(ch);
> +}
> +
> +static int sbi_serial_tstc(struct console_device *cdev)
> +{
> +       struct sbi_serial_priv *priv = cdev->dev->priv;
> +       int c = sbi_console_getchar();
> +
> +       if (c != -1)
> +               priv->b[priv->tail++ & 0x1] = c;
> +       return priv->head != priv->tail;
> +}
> +
> +static int sbi_serial_probe(struct device_d *dev)
> +{
> +       struct sbi_serial_priv *priv;
> +
> +       priv = dev->priv = xzalloc(sizeof(*priv));
> +       priv->cdev.dev    = dev;
> +       priv->cdev.putc   = sbi_serial_putc;
> +       priv->cdev.getc   = sbi_serial_getc;
> +       priv->cdev.tstc   = sbi_serial_tstc;
> +       priv->cdev.flush  = 0;
> +       priv->cdev.setbrg = 0;
> +
> +       return console_register(&priv->cdev);
> +}
> +
> +static struct driver_d serial_sbi_driver = {
> +       .name   = "riscv-serial-sbi",
> +       .probe  = sbi_serial_probe,
> +};
> +postcore_platform_driver(serial_sbi_driver);
> --
> 2.32.0
> 
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-- 
Best regards,
  Antony Pavlov