Re: [PATCH 12/17] tty: New RISC-V SBI Console Driver

[Geert Uytterhoeven]

CC (hypervisor) console folks

On Wed, Jun 7, 2017 at 1:00 AM, Palmer Dabbelt <palmer@xxxxxxxxxxx> wrote:
> This patch adds a new driver for the console availiable via the RISC-V
> SBI.  This console is specified to be used for early boot messages, and
> is designed to be a very simple (albiet somewhat slow) console that is
> always availiable.  All RISC-V systems have an SBI console.
>
> The SBI console is made availiable for early printk messages and is also
> availiable as a regular console.
>
> Signed-off-by: Palmer Dabbelt <palmer@xxxxxxxxxxx>
> ---
>  drivers/tty/hvc/Kconfig   |  11 +++++
>  drivers/tty/hvc/Makefile  |   1 +
>  drivers/tty/hvc/hvc_sbi.c | 102 ++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 114 insertions(+)
>  create mode 100644 drivers/tty/hvc/hvc_sbi.c
>
> diff --git a/drivers/tty/hvc/Kconfig b/drivers/tty/hvc/Kconfig
> index 574da15fe618..f3774adab240 100644
> --- a/drivers/tty/hvc/Kconfig
> +++ b/drivers/tty/hvc/Kconfig
> @@ -114,4 +114,15 @@ config HVCS
>           which will also be compiled when this driver is built as a
>           module.
>
> +config HVC_SBI
> +       bool "SBI console support"
> +       depends on RISCV
> +       select HVC_DRIVER
> +       default y
> +       help
> +         This enables support for console output via RISC-V SBI calls, which
> +         is normally used only during boot to output printk.
> +
> +         If you don't know what do to here, say Y.
> +
>  endif # TTY
> diff --git a/drivers/tty/hvc/Makefile b/drivers/tty/hvc/Makefile
> index 6a2702be76d1..2d63bfe4a96b 100644
> --- a/drivers/tty/hvc/Makefile
> +++ b/drivers/tty/hvc/Makefile
> @@ -11,3 +11,4 @@ obj-$(CONFIG_HVC_IUCV)                += hvc_iucv.o
>  obj-$(CONFIG_HVC_UDBG)         += hvc_udbg.o
>  obj-$(CONFIG_HVC_BFIN_JTAG)    += hvc_bfin_jtag.o
>  obj-$(CONFIG_HVCS)             += hvcs.o
> +obj-$(CONFIG_HVC_SBI)          += hvc_sbi.o
> diff --git a/drivers/tty/hvc/hvc_sbi.c b/drivers/tty/hvc/hvc_sbi.c
> new file mode 100644
> index 000000000000..e70293fb7b35
> --- /dev/null
> +++ b/drivers/tty/hvc/hvc_sbi.c
> @@ -0,0 +1,102 @@
> +/*
> + * RISC-V SBI interface to hvc_console.c
> + *  based on drivers-tty/hvc/hvc_udbg.c
> + *
> + * Copyright (C) 2008 David Gibson, IBM Corporation
> + * Copyright (C) 2012 Regents of the University of California
> + *
> + *   This program is free software; you can redistribute it and/or
> + *   modify it under the terms of the GNU General Public License
> + *   as published by the Free Software Foundation, version 2.
> + *
> + *   This program is distributed in the hope that it will be useful,
> + *   but WITHOUT ANY WARRANTY; without even the implied warranty of
> + *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + *   GNU General Public License for more details.
> + */
> +
> +#include <linux/console.h>
> +#include <linux/delay.h>
> +#include <linux/err.h>
> +#include <linux/init.h>
> +#include <linux/moduleparam.h>
> +#include <linux/types.h>
> +#include <linux/irq.h>
> +
> +#include <asm/sbi.h>
> +
> +#include "hvc_console.h"
> +
> +static int hvc_sbi_tty_put(uint32_t vtermno, const char *buf, int count)
> +{
> +       int i;
> +
> +       for (i = 0; i < count; i++)
> +               sbi_console_putchar(buf[i]);
> +
> +       return i;
> +}
> +
> +static int hvc_sbi_tty_get(uint32_t vtermno, char *buf, int count)
> +{
> +       int i, c;
> +
> +       for (i = 0; i < count; i++) {
> +               if ((c = sbi_console_getchar()) < 0)
> +                       break;
> +               buf[i] = c;
> +       }
> +
> +       return i;
> +}
> +
> +static const struct hv_ops hvc_sbi_ops = {
> +       .get_chars = hvc_sbi_tty_get,
> +       .put_chars = hvc_sbi_tty_put,
> +};
> +
> +static int __init hvc_sbi_init(void)
> +{
> +       return PTR_ERR_OR_ZERO(hvc_alloc(0, 0, &hvc_sbi_ops, 16));
> +}
> +device_initcall(hvc_sbi_init);
> +
> +static int __init hvc_sbi_console_init(void)
> +{
> +       hvc_instantiate(0, 0, &hvc_sbi_ops);
> +       add_preferred_console("hvc", 0, NULL);
> +
> +       return 0;
> +}
> +console_initcall(hvc_sbi_console_init);
> +
> +#ifdef CONFIG_EARLY_PRINTK
> +static void sbi_console_write(struct console *co, const char *buf,
> +                             unsigned int n)
> +{
> +       int i;
> +
> +       for (i = 0; i < n; ++i) {
> +               if (buf[i] == '\n')
> +                       sbi_console_putchar('\r');
> +               sbi_console_putchar(buf[i]);
> +       }
> +}
> +
> +static struct console early_console_dev __initdata = {
> +       .name   = "early",
> +       .write  = sbi_console_write,
> +       .flags  = CON_PRINTBUFFER | CON_BOOT,
> +       .index  = -1
> +};
> +
> +static int __init setup_early_printk(char *str)
> +{
> +       if (early_console == NULL) {
> +               early_console = &early_console_dev;
> +               register_console(early_console);
> +       }
> +       return 0;
> +}
> +early_param("earlyprintk", setup_early_printk);
> +#endif
> --
> 2.13.0