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-rw-r--r--arch/arm64/kernel/early_printk.c118
1 files changed, 118 insertions, 0 deletions
diff --git a/arch/arm64/kernel/early_printk.c b/arch/arm64/kernel/early_printk.c
new file mode 100644
index 000000000000..7e320a2edb9b
--- /dev/null
+++ b/arch/arm64/kernel/early_printk.c
@@ -0,0 +1,118 @@
+/*
+ * Earlyprintk support.
+ *
+ * Copyright (C) 2012 ARM Ltd.
+ * Author: Catalin Marinas <catalin.marinas@arm.com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * 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.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+#include <linux/kernel.h>
+#include <linux/console.h>
+#include <linux/init.h>
+#include <linux/string.h>
+#include <linux/mm.h>
+#include <linux/io.h>
+
+#include <linux/amba/serial.h>
+
+static void __iomem *early_base;
+static void (*printch)(char ch);
+
+/*
+ * PL011 single character TX.
+ */
+static void pl011_printch(char ch)
+{
+ while (readl_relaxed(early_base + UART01x_FR) & UART01x_FR_TXFF)
+ ;
+ writeb_relaxed(ch, early_base + UART01x_DR);
+ while (readl_relaxed(early_base + UART01x_FR) & UART01x_FR_BUSY)
+ ;
+}
+
+struct earlycon_match {
+ const char *name;
+ void (*printch)(char ch);
+};
+
+static const struct earlycon_match earlycon_match[] __initconst = {
+ { .name = "pl011", .printch = pl011_printch, },
+ {}
+};
+
+static void early_write(struct console *con, const char *s, unsigned n)
+{
+ while (n-- > 0) {
+ if (*s == '\n')
+ printch('\r');
+ printch(*s);
+ s++;
+ }
+}
+
+static struct console early_console = {
+ .name = "earlycon",
+ .write = early_write,
+ .flags = CON_PRINTBUFFER | CON_BOOT,
+ .index = -1,
+};
+
+/*
+ * Parse earlyprintk=... parameter in the format:
+ *
+ * <name>[,<addr>][,<options>]
+ *
+ * and register the early console. It is assumed that the UART has been
+ * initialised by the bootloader already.
+ */
+static int __init setup_early_printk(char *buf)
+{
+ const struct earlycon_match *match = earlycon_match;
+ phys_addr_t paddr = 0;
+
+ if (!buf) {
+ pr_warning("No earlyprintk arguments passed.\n");
+ return 0;
+ }
+
+ while (match->name) {
+ size_t len = strlen(match->name);
+ if (!strncmp(buf, match->name, len)) {
+ buf += len;
+ break;
+ }
+ match++;
+ }
+ if (!match->name) {
+ pr_warning("Unknown earlyprintk arguments: %s\n", buf);
+ return 0;
+ }
+
+ /* I/O address */
+ if (!strncmp(buf, ",0x", 3)) {
+ char *e;
+ paddr = simple_strtoul(buf + 1, &e, 16);
+ buf = e;
+ }
+ /* no options parsing yet */
+
+ if (paddr)
+ early_base = early_io_map(paddr, EARLYCON_IOBASE);
+
+ printch = match->printch;
+ register_console(&early_console);
+
+ return 0;
+}
+
+early_param("earlyprintk", setup_early_printk);