earlycon: prevent multiple register_console()

If the earlycon parameter is given twice, the kernel will spit out a
WARN() in register_console() because it was already registered. The
non-dt variant setup_earlycon() already handles that gracefully. The dt
variant of_setup_earlycon() doesn't. Add the check there and add the
-EALREADY handling in early_init_dt_scan_chosen_stdout().

FWIW, this doesn't happen if CONFIG_ACPI_SPCR_TABLE is set. In that case
the registration is delayed until after earlycon parameter(s) are
parsed.

Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Michael Walle <michael@walle.cc>
Link: https://lore.kernel.org/r/20220628120705.200617-1-michael@walle.cc
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/drivers/tty/serial/earlycon.c b/drivers/tty/serial/earlycon.c
index 57c70851f22a..88d08ba1ca83 100644
--- a/drivers/tty/serial/earlycon.c
+++ b/drivers/tty/serial/earlycon.c
@@ -253,6 +253,9 @@ int __init of_setup_earlycon(const struct earlycon_id *match,
 	bool big_endian;
 	u64 addr;
 
+	if (early_con.flags & CON_ENABLED)
+		return -EALREADY;
+
 	spin_lock_init(&port->lock);
 	port->iotype = UPIO_MEM;
 	addr = of_flat_dt_translate_address(node);