Revert "arm64: remove arch specific earlyprintk"

This reverts commit 8ef0ed95ee040a5cd25325dddcb8292c34bec33e.

Conflicts:

	arch/arm64/kernel/Makefile

Signed-off-by: Georgi Djakov <georgi.djakov@linaro.org>

3 files changed, 168 insertions, 0 deletions

diff --git a/arch/arm64/Kconfig.debug b/arch/arm64/Kconfig.debug
index 4a8741073c9..d6ba752e8d1 100644
--- a/arch/arm64/Kconfig.debug
+++ b/arch/arm64/Kconfig.debug
@@ -32,6 +32,15 @@ config STRICT_DEVMEM
 
 	  If in doubt, say Y.
 
+config EARLY_PRINTK
+	bool "Early printk support"
+	default y
+	help
+	  Say Y here if you want to have an early console using the
+	  earlyprintk=<name>[,<addr>][,<options>] kernel parameter. It
+	  is assumed that the early console device has been initialised
+	  by the boot loader prior to starting the Linux kernel.
+
 config PID_IN_CONTEXTIDR
 	bool "Write the current PID to the CONTEXTIDR register"
 	help
diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
index bef04afd603..169c429e63e 100644
--- a/arch/arm64/kernel/Makefile
+++ b/arch/arm64/kernel/Makefile
@@ -29,6 +29,7 @@ arm64-obj-$(CONFIG_HW_PERF_EVENTS)	+= perf_event.o
 arm64-obj-$(CONFIG_HAVE_HW_BREAKPOINT)	+= hw_breakpoint.o
 arm64-obj-$(CONFIG_CPU_PM)		+= sleep.o suspend.o
 arm64-obj-$(CONFIG_CPU_IDLE)		+= cpuidle.o
+arm64-obj-$(CONFIG_EARLY_PRINTK)	+= early_printk.o
 arm64-obj-$(CONFIG_JUMP_LABEL)		+= jump_label.o
 arm64-obj-$(CONFIG_KGDB)		+= kgdb.o
 arm64-obj-$(CONFIG_EFI)			+= efi.o efi-stub.o efi-entry.o
diff --git a/arch/arm64/kernel/early_printk.c b/arch/arm64/kernel/early_printk.c
new file mode 100644
index 00000000000..ffbbdde7aba
--- /dev/null
+++ b/arch/arm64/kernel/early_printk.c
@@ -0,0 +1,158 @@
+/*
+ * 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>
+#include <linux/serial_reg.h>
+
+#include <asm/fixmap.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)
+		;
+}
+
+/*
+ * Semihosting-based debug console
+ */
+static void smh_printch(char ch)
+{
+	asm volatile("mov  x1, %0\n"
+		     "mov  x0, #3\n"
+		     "hlt  0xf000\n"
+		     : : "r" (&ch) : "x0", "x1", "memory");
+}
+
+/*
+ * 8250/16550 (8-bit aligned registers) single character TX.
+ */
+static void uart8250_8bit_printch(char ch)
+{
+	while (!(readb_relaxed(early_base + UART_LSR) & UART_LSR_THRE))
+		;
+	writeb_relaxed(ch, early_base + UART_TX);
+}
+
+/*
+ * 8250/16550 (32-bit aligned registers) single character TX.
+ */
+static void uart8250_32bit_printch(char ch)
+{
+	while (!(readl_relaxed(early_base + (UART_LSR << 2)) & UART_LSR_THRE))
+		;
+	writel_relaxed(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 = "pl011", .printch = pl011_printch, },
+	{ .name = "smh", .printch = smh_printch, },
+	{ .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;
+	}
+	/* no options parsing yet */
+
+	if (paddr) {
+		set_fixmap_io(FIX_EARLYCON_MEM_BASE, paddr);
+		early_base = (void __iomem *)fix_to_virt(FIX_EARLYCON_MEM_BASE);
+	}
+
+	printch = match->printch;
+	early_console = &early_console_dev;
+	register_console(&early_console_dev);
+
+	return 0;
+}
+
+early_param("earlyprintk", setup_early_printk);