[MIPS] Qemu: Add early printk, your friend in a cold night.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/Kconfig

@@ -361,10 +361,10 @@ config QEMU
 	select PCSPEAKER
 	select SWAP_IO_SPACE
 	select SYS_HAS_CPU_MIPS32_R1
+	select SYS_HAS_EARLY_PRINTK
 	select SYS_SUPPORTS_32BIT_KERNEL
 	select SYS_SUPPORTS_BIG_ENDIAN
 	select SYS_SUPPORTS_LITTLE_ENDIAN
-	select ARCH_SPARSEMEM_ENABLE
 	select GENERIC_HARDIRQS_NO__DO_IRQ
 	select NR_CPUS_DEFAULT_1
 	select SYS_SUPPORTS_SMP

arch/mips/qemu/Makefile

@@ -4,6 +4,7 @@
 
 obj-y		= q-firmware.o q-irq.o q-mem.o q-setup.o q-reset.o
 
+obj-$(CONFIG_EARLY_PRINTK)	+= q-console.o
 obj-$(CONFIG_SMP)		+= q-smp.o
 
 EXTRA_CFLAGS += -Werror

arch/mips/qemu/q-console.c

@@ -0,0 +1,26 @@
+#include <linux/console.h>
+#include <linux/init.h>
+#include <linux/serial_reg.h>
+#include <asm/io.h>
+
+#define PORT(offset) (0x3f8 + (offset))
+
+static inline unsigned int serial_in(int offset)
+{
+	return inb(PORT(offset));
+}
+
+static inline void serial_out(int offset, int value)
+{
+	outb(value, PORT(offset));
+}
+
+int prom_putchar(char c)
+{
+	while ((serial_in(UART_LSR) & UART_LSR_THRE) == 0)
+		;
+
+	serial_out(UART_TX, c);
+
+	return 1;
+}

arch/mips/qemu/q-firmware.c

@@ -2,6 +2,9 @@
 #include <linux/string.h>
 #include <asm/addrspace.h>
 #include <asm/bootinfo.h>
+#include <asm/io.h>
+
+#define QEMU_PORT_BASE 0xb4000000
 
 void __init prom_init(void)
 {
@@ -15,4 +18,7 @@ void __init prom_init(void)
 	} else {
 		add_memory_region(0x0<<20, 0x10<<20, BOOT_MEM_RAM);
 	}
+
+
+	set_io_port_base(QEMU_PORT_BASE);
 }

arch/mips/qemu/q-setup.c

@@ -6,8 +6,6 @@
 
 extern void qemu_reboot_setup(void);
 
-#define QEMU_PORT_BASE 0xb4000000
-
 const char *get_system_type(void)
 {
 	return "Qemu";
@@ -20,6 +18,5 @@ void __init plat_time_init(void)
 
 void __init plat_mem_setup(void)
 {
-	set_io_port_base(QEMU_PORT_BASE);
 	qemu_reboot_setup();
 }