dm: serial: Add a REQUIRE_SERIAL_CONSOLE option for boards with no serial port

Currently the serial code assumes that there is always at least one serial
port (and panics / crashes due to null pointer dereferences when there is
none).

This makes it impossible to use u-boot on boards where there is no (debug)
serial port, because e.g. all uart pins are muxed to another function.

This commit adds a CONFIG_REQUIRE_SERIAL_CONSOLE Kconfig option, which
defaults to y (preserving existing behavior), which can be set to n on
such boards to make them work.

This commit only implements this for CONFIG_DM_SERIAL=y configs, as allowing
running without a serial port for CONFIG_DM_SERIAL=n configs is non trivial,
and is not necessary at this moment.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Simon Glass <sjg@chromium.org>

1 files changed, 11 insertions, 0 deletions

diff --git a/drivers/serial/Kconfig b/drivers/serial/Kconfig
index fd126a8..a880eac 100644
--- a/drivers/serial/Kconfig
+++ b/drivers/serial/Kconfig
@@ -1,3 +1,14 @@
+config REQUIRE_SERIAL_CONSOLE
+	bool "Require a serial port for console"
+	# Running without a serial console is not supported by the
+	# non-dm serial code
+	depends on DM_SERIAL
+	default y
+	help
+	  Require a serial port for the console, and panic if none is found
+	  during serial port initialization (default y). Set this to n on
+	  boards which have no debug serial port whatsoever.
+
 config DM_SERIAL
 	bool "Enable Driver Model for serial drivers"
 	depends on DM