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MIPS, ttyFDC: Add early FDC console support

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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@imgtec.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/9145/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
This commit is contained in:
James Hogan 2015-01-29 11:14:13 +00:00 committed by Ralf Baechle
parent 4cebec609a
commit e934945db7
4 changed files with 46 additions and 0 deletions
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11
arch/mips/include/asm/cdmm.h
View file

@ -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 */

2
arch/mips/kernel/setup.c
View file

@ -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

13
drivers/tty/Kconfig
View file

@ -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

20
drivers/tty/mips_ejtag_fdc.c
View file

@ -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