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tty: New RISC-V SBI console driver

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The RISC-V ISA defines a simple console that is availiable via SBI calls
on all systems.  The SBI console is designed to be availiable at all
times, so while it's most natural to use this as an early printk target
it's also possible to use this as the system console when there isn't a
better one availiable.

This patch adds support for the RISC-V SBI console via the HVC
infastructure.  It's entirely independent from our early printk support,
which results in early boot messages appearing twice over the SBI
console.  As far as I can tell that's the fault of our early printk
support (we should support earlycon) as opposed to this driver.

There is one checkpatch.pl warning here: to check the MAINTAINERS file.
They're all matched by the "K: riscv" line.

Signed-off-by: Palmer Dabbelt <palmer@sifive.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Palmer Dabbelt 2018-03-08 14:27:34 -08:00 committed by Greg Kroah-Hartman
parent 6aed2a8850
commit afa6b1ccfa
3 changed files with 71 additions and 0 deletions
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10
drivers/tty/hvc/Kconfig
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@ -97,6 +97,16 @@ config HVC_BFIN_JTAG
the HVC driver. If you don't have JTAG, then you probably don't
want this option.
config HVC_RISCV_SBI
bool "RISC-V SBI console support"
depends on RISCV
select HVC_DRIVER
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.
config HVCS
tristate "IBM Hypervisor Virtual Console Server support"
depends on PPC_PSERIES && HVC_CONSOLE

1
drivers/tty/hvc/Makefile
View File

@ -11,4 +11,5 @@ obj-$(CONFIG_HVC_XEN) += hvc_xen.o
obj-$(CONFIG_HVC_IUCV) += hvc_iucv.o
obj-$(CONFIG_HVC_UDBG) += hvc_udbg.o
obj-$(CONFIG_HVC_BFIN_JTAG) += hvc_bfin_jtag.o
obj-$(CONFIG_HVC_RISCV_SBI) += hvc_riscv_sbi.o
obj-$(CONFIG_HVCS) += hvcs.o

60
drivers/tty/hvc/hvc_riscv_sbi.c Normal file
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@ -0,0 +1,60 @@
/* SPDX-License-Identifier: GPL-2.0 */
/*
* Copyright (C) 2008 David Gibson, IBM Corporation
* Copyright (C) 2012 Regents of the University of California
* Copyright (C) 2017 SiFive
*/
#include <linux/console.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/moduleparam.h>
#include <linux/types.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++) {
c = sbi_console_getchar();
if (c < 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);