superio/fintek/*: Factor out generic romstage component

The romstage of Fintek Super I/O's is identical, leading to replication
of essentially the same code prone to bitrot. Herein we consolidate the
early pre-ram UART initialisation code into fintek/common, rather we
leave the exceptions to be implemented under model/.

More precisely we provide a well documented version of early_serial.c
under fintek/common and select by way of Kconfig as a generic romstage
component to Super I/O support. We leave future Super I/O's the option
to implement `non-standard` initialisation code should such a (unlikely)
need araise. A primary advantage is that new support for romstage serial
is now trival to add. We also provide some Kconfig documentation while
here.

Change-Id: I3c62561558a62ece944a167ba302fb7076bba001
Signed-off-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Reviewed-on: http://review.coreboot.org/5575
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <patrick@georgi-clan.de>

1 files changed, 72 insertions, 0 deletions

diff --git a/src/superio/fintek/common/early_serial.c b/src/superio/fintek/common/early_serial.c
new file mode 100644
index 0000000000..d74b786d50
--- /dev/null
+++ b/src/superio/fintek/common/early_serial.c
@@ -0,0 +1,72 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * Copyright (C) 2014 Edward O'Callaghan <eocallaghan@alterapraxis.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/*
+ * A generic romstage (pre-ram) driver for Fintek variant Super I/O chips.
+ *
+ * The following is derived directly from the vendor Fintek's data-sheets:
+ *
+ * To toggle between `configuration mode` and `normal operation mode` as to
+ * manipulation the various LDN's in Fintek Super I/O's we are required to pass
+ * magic numbers `passwords keys`.
+ *
+ *  FINTEK_ENTRY_KEY :=  enable  configuration : 0x87
+ *  FINTEK_EXIT_KEY  :=  disable configuration : 0xAA
+ *
+ * To modify a LDN's configuration register, we use the index port to select
+ * the index of the LDN and then writing to the data port to alter the
+ * parameters. A default index, data port pair is 0x4E, 0x4F respectively, a
+ * user modified pair is 0x2E, 0x2F respectively.
+ *
+ */
+
+#include <arch/io.h>
+#include <device/pnp.h>
+#include <stdint.h>
+#include "fintek.h"
+
+#define FINTEK_ENTRY_KEY 0x87
+#define FINTEK_EXIT_KEY 0xAA
+
+/* Enable configuration: pass entry key '0x87' into index port dev. */
+static void pnp_enter_conf_state(device_t dev)
+{
+	u16 port = dev >> 8;
+	outb(FINTEK_ENTRY_KEY, port);
+	outb(FINTEK_ENTRY_KEY, port);
+}
+
+/* Disable configuration: pass exit key '0xAA' into index port dev. */
+static void pnp_exit_conf_state(device_t dev)
+{
+	u16 port = dev >> 8;
+	outb(FINTEK_EXIT_KEY, port);
+}
+
+/* Bring up early serial debugging output before the RAM is initialized. */
+void fintek_enable_serial(device_t dev, u16 iobase)
+{
+	pnp_enter_conf_state(dev);
+	pnp_set_logical_device(dev);
+	pnp_set_enable(dev, 0);
+	pnp_set_iobase(dev, PNP_IDX_IO0, iobase);
+	pnp_set_enable(dev, 1);
+	pnp_exit_conf_state(dev);
+}