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Subject[PATCH v8 09/18] 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. This patch adds a driver for this console interface
that can act as both a target for early printk and as the system
console.

Signed-off-by: Palmer Dabbelt <palmer@dabbelt.com>
---
arch/riscv/include/asm/hvc_riscv_sbi.h | 25 ++++++++++
drivers/tty/hvc/Kconfig | 11 +++++
drivers/tty/hvc/Makefile | 1 +
drivers/tty/hvc/hvc_riscv_sbi.c | 90 ++++++++++++++++++++++++++++++++++
4 files changed, 127 insertions(+)
create mode 100644 arch/riscv/include/asm/hvc_riscv_sbi.h
create mode 100644 drivers/tty/hvc/hvc_riscv_sbi.c

diff --git a/arch/riscv/include/asm/hvc_riscv_sbi.h b/arch/riscv/include/asm/hvc_riscv_sbi.h
new file mode 100644
index 000000000000..d4f3cf0c17e9
--- /dev/null
+++ b/arch/riscv/include/asm/hvc_riscv_sbi.h
@@ -0,0 +1,25 @@
+/*
+ * RISC-V SBI console interface
+ *
+ * Copyright (C) 2017 SiFive
+ *
+ * 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.
+ */
+
+#ifndef _ASM_RISCV_HVC_RISCV_SBI_H
+#define _ASM_RISCV_HVC_RISCV_SBI_H
+
+/*
+ * We always support CONFIG_EARLY_PRINTK via the SBI console driver because it
+ * works well enough that there's no penalty to doing so.
+ */
+extern struct console riscv_sbi_early_console_dev __initdata;
+
+#endif
diff --git a/drivers/tty/hvc/Kconfig b/drivers/tty/hvc/Kconfig
index b8d5ea0ae26b..abe331761bdb 100644
--- a/drivers/tty/hvc/Kconfig
+++ b/drivers/tty/hvc/Kconfig
@@ -97,6 +97,17 @@ 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
+ 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.
+
config HVCS
tristate "IBM Hypervisor Virtual Console Server support"
depends on PPC_PSERIES && HVC_CONSOLE
diff --git a/drivers/tty/hvc/Makefile b/drivers/tty/hvc/Makefile
index 6a2702be76d1..be497f9312d1 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_RISCV_SBI) += hvc_riscv_sbi.o
diff --git a/drivers/tty/hvc/hvc_riscv_sbi.c b/drivers/tty/hvc/hvc_riscv_sbi.c
new file mode 100644
index 000000000000..2548d658e110
--- /dev/null
+++ b/drivers/tty/hvc/hvc_riscv_sbi.c
@@ -0,0 +1,90 @@
+/*
+ * 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
+ * Copyright (C) 2017 SiFive
+ *
+ * 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/err.h>
+#include <linux/init.h>
+#include <linux/moduleparam.h>
+#include <linux/types.h>
+
+#include <asm/sbi.h>
+#include <asm/hvc_riscv_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);
+
+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]);
+ }
+}
+
+struct console riscv_sbi_early_console_dev __initdata = {
+ .name = "early",
+ .write = sbi_console_write,
+ .flags = CON_PRINTBUFFER | CON_BOOT | CON_ANYTIME,
+ .index = -1
+};
--
2.13.5
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