Add console wrapper for UART driver

Coreboot is designed to have a single serial console at most, on top
of that it may have a CBMEM (virtual) console. Matters are complicated
by the fact that console interface is different between bootblock and
later stages.

A linker list of console driver descriptors is used to allow to
determine the set and type of console drivers at compile time. Even
though the upstream seems to have done away with this approach, which
does not seem the best idea.

As an alternative this patch introduces a common wrapper which
different UART drivers can plug in into. The driver exports a single
API which can be used both directly (in bootblock) and through the
wrapper (in later stages).

The existing drivers can be adjusted to fit this scheme one by one.
The common UART driver API also aligns fine with the upstream
approach.

BUG=chrome-os-partner:27784
TEST=none yet

Original-Change-Id: Id1fe73d29f2a3c722bd77180beebaedb9bf7d6a1
Original-Signed-off-by: Vadim Bendebury <vbendeb@chromium.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/196660
Original-Reviewed-by: Stefan Reinauer <reinauer@chromium.org>
(cherry picked from commit 94a36ad79a96f83d283c0fd073b05f98ae48820c)
Signed-off-by: Marc Jones <marc.jones@se-eng.com>

Change-Id: Id1fe73d29f2a3c722bd77180beebaedb9bf7d6a1
Reviewed-on: http://review.coreboot.org/7872
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

1 files changed, 14 insertions, 0 deletions

diff --git a/src/include/console/console.h b/src/include/console/console.h
index b5de7d7f44..b0971e5323 100644
--- a/src/include/console/console.h
+++ b/src/include/console/console.h
@@ -26,6 +26,20 @@
 #include <console/loglevel.h>
 
 #ifndef __ROMCC__
+struct console_driver {
+	void (*init)(int);
+	void (*tx_byte)(int, unsigned char byte);
+	void (*tx_flush)(int);
+	unsigned char (*rx_byte)(int);
+	int (*tst_byte)(void);
+};
+
+#define __console	__attribute__((used, __section__ (".rodata.console_drivers")))
+
+/* Defined by the linker... */
+extern struct console_driver console_drivers[];
+extern struct console_driver econsole_drivers[];
+
 void post_code(u8 value);
 #if CONFIG_CMOS_POST_EXTRA
 void post_log_extra(u32 value);