MIPS, ttyFDC: Add early FDC console support
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>
diff --git a/drivers/tty/Kconfig b/drivers/tty/Kconfig
index 39469ca..e0c18e5 100644
--- a/drivers/tty/Kconfig
+++ b/drivers/tty/Kconfig
@@ -437,4 +437,17 @@
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 51672cf..8d9bf6f 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 @@
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