Add support for early console of MIPS Fast Debug Channel (FDC) on
channel 1 with a call very early from the MIPS setup_arch().
Signed-off-by: James Hogan <james.hogan@xxxxxxxxxx>
Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: Jiri Slaby <jslaby@xxxxxxx>
Cc: linux-mips@xxxxxxxxxxxxxx
---
arch/mips/include/asm/cdmm.h | 11 +++++++++++
arch/mips/kernel/setup.c | 2 ++
drivers/tty/Kconfig | 13 +++++++++++++
drivers/tty/mips_ejtag_fdc.c | 20 ++++++++++++++++++++
4 files changed, 46 insertions(+)
diff --git a/arch/mips/include/asm/cdmm.h b/arch/mips/include/asm/cdmm.h
index b7d520f28d30..16e22ce9719f 100644
--- a/arch/mips/include/asm/cdmm.h
+++ b/arch/mips/include/asm/cdmm.h
@@ -84,4 +84,15 @@ void mips_cdmm_driver_unregister(struct mips_cdmm_driver *);
module_driver(__mips_cdmm_driver, mips_cdmm_driver_register, \
mips_cdmm_driver_unregister)
+/* drivers/tty/mips_ejtag_fdc.c */
+
+#ifdef CONFIG_MIPS_EJTAG_FDC_EARLYCON
+int setup_early_fdc_console(void);
+#else
+static inline int setup_early_fdc_console(void)
+{
+ return -ENODEV;
+}
+#endif
+
#endif /* __ASM_CDMM_H */
diff --git a/arch/mips/kernel/setup.c b/arch/mips/kernel/setup.c
index 058929041368..be73c491182b 100644
--- a/arch/mips/kernel/setup.c
+++ b/arch/mips/kernel/setup.c
@@ -31,6 +31,7 @@
#include <asm/bootinfo.h>
#include <asm/bugs.h>
#include <asm/cache.h>
+#include <asm/cdmm.h>
#include <asm/cpu.h>
#include <asm/sections.h>
#include <asm/setup.h>
@@ -763,6 +764,7 @@ void __init setup_arch(char **cmdline_p)
cpu_probe();
prom_init();
+ setup_early_fdc_console();
#ifdef CONFIG_EARLY_PRINTK
setup_early_printk();
#endif
diff --git a/drivers/tty/Kconfig b/drivers/tty/Kconfig
index 39469ca4231c..e0c18e5b7057 100644
--- a/drivers/tty/Kconfig
+++ b/drivers/tty/Kconfig
@@ -437,4 +437,17 @@ config MIPS_EJTAG_FDC_TTY
If unsure, say N.
+config MIPS_EJTAG_FDC_EARLYCON
+ bool "Early FDC console"
+ depends on MIPS_EJTAG_FDC_TTY
+ help
+ This registers a console on FDC channel 1 very early during boot (from
+ MIPS arch code). This is useful for bring-up and debugging early boot
+ issues.
+
+ Do not enable unless there is a debug probe attached to drain the FDC
+ TX FIFO.
+
+ If unsure, say N.
+
endif # TTY
diff --git a/drivers/tty/mips_ejtag_fdc.c b/drivers/tty/mips_ejtag_fdc.c
index 51672cfe7e45..8d9bf6f90110 100644
--- a/drivers/tty/mips_ejtag_fdc.c
+++ b/drivers/tty/mips_ejtag_fdc.c
@@ -69,6 +69,9 @@
#define REG_FDSTAT_TXE BIT(1) /* Tx Empty */
#define REG_FDSTAT_TXF BIT(0) /* Tx Full */
+/* Default channel for the early console */
+#define CONSOLE_CHANNEL 1
+
#define NUM_TTY_CHANNELS 16
#define RX_BUF_SIZE 1024
@@ -1124,3 +1127,20 @@ static int __init mips_ejtag_fdc_init_console(void)
return mips_ejtag_fdc_console_init(&mips_ejtag_fdc_con);
}
console_initcall(mips_ejtag_fdc_init_console);
+
+#ifdef CONFIG_MIPS_EJTAG_FDC_EARLYCON
+static struct mips_ejtag_fdc_console mips_ejtag_fdc_earlycon = {
+ .cons = {
+ .name = "early_fdc",
+ .write = mips_ejtag_fdc_console_write,
+ .flags = CON_PRINTBUFFER | CON_BOOT,
+ .index = CONSOLE_CHANNEL,
+ },
+ .lock = __RAW_SPIN_LOCK_UNLOCKED(mips_ejtag_fdc_earlycon.lock),
+};
+
+int __init setup_early_fdc_console(void)
+{
+ return mips_ejtag_fdc_console_init(&mips_ejtag_fdc_earlycon);
+}
+#endif
--
2.0.5
