[PATCH 03/31] nds32: Support early_printk

[Greentime Hu]

From: Greentime Hu <greentime@xxxxxxxxxxxxx>

Signed-off-by: Rick Chen <rick@xxxxxxxxxxxxx>
Signed-off-by: Greentime Hu <greentime@xxxxxxxxxxxxx>
---
 arch/nds32/kernel/early_printk.c |  124 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 124 insertions(+)
 create mode 100644 arch/nds32/kernel/early_printk.c

diff --git a/arch/nds32/kernel/early_printk.c b/arch/nds32/kernel/early_printk.c
new file mode 100644
index 0000000..269c3cd
--- /dev/null
+++ b/arch/nds32/kernel/early_printk.c
@@ -0,0 +1,124 @@
+/*
+ * Copyright (C) 2005-2017 Andes Technology Corporation
+ *
+ * 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/io.h>
+
+#include <linux/serial_reg.h>
+
+extern void __iomem *early_io_map(phys_addr_t phys);
+static void __iomem *early_base;
+static void (*printch) (char ch);
+
+/*
+ * 8250/16550 (8-bit aligned registers) single character TX.
+ */
+static void uart8250_8bit_printch(char ch)
+{
+	while (!(readb(early_base + UART_LSR) & UART_LSR_THRE)) ;
+	writeb(ch, early_base + UART_TX);
+}
+
+/*
+ * 8250/16550 (32-bit aligned registers) single character TX.
+ */
+static void uart8250_32bit_printch(char ch)
+{
+	while (!(readl(early_base + (UART_LSR << 2)) & UART_LSR_THRE)) ;
+	writel(ch, early_base + (UART_TX << 2));
+}
+
+struct earlycon_match {
+	const char *name;
+	void (*printch) (char ch);
+};
+
+static const struct earlycon_match earlycon_match[] __initconst = {
+	{.name = "uart8250-8bit",.printch = uart8250_8bit_printch,},
+	{.name = "uart8250-32bit",.printch = uart8250_32bit_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_dev = {
+	.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;
+	}
+
+	if (paddr)
+		early_base = early_io_map(paddr);
+
+	if (!strcmp(CONFIG_NDS32_BUILTIN_DTB, "ae3xx"))
+		early_base += 32;
+
+	printch = match->printch;
+	register_console(&early_console_dev);
+
+	return 0;
+}
+
+early_param("earlyprintk", setup_early_printk);
-- 
1.7.9.5