drivers/smbus: add smbus console driver

This patch adds a new smbus console driver and Kconfig
options to enable the driver.

Change-Id: Ife77fb2c3e1cc77678a4972701317d50624ceb95
Signed-off-by: Husni Faiz <ahamedhusni73@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/67339
Reviewed-by: Raul Rangel <rrangel@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/console/Kconfig

@@ -297,6 +297,30 @@ config CONSOLE_SPI_FLASH_BUFFER_SIZE
 	  value (128K or 0x20000 bytes) is large enough to accommodate
 	  even the BIOS_SPEW level.
 
+config CONSOLE_I2C_SMBUS
+	bool "SMBus console output"
+	depends on SOUTHBRIDGE_INTEL_COMMON_SMBUS
+	help
+	  Send coreboot debug output to the SMBus.
+	  The output can be read with an I2C slave device connected
+	  the SMBus. Please refer to the technotes section of the
+	  coreboot documentation for more details.
+
+if CONSOLE_I2C_SMBUS
+	comment "Set logging device address and data register address"
+
+config CONSOLE_I2C_SMBUS_SLAVE_ADDRESS
+	hex "I2C slave address of the logging device"
+	help
+	  I2C address of the device which logs the data.
+
+config CONSOLE_I2C_SMBUS_SLAVE_DATA_REGISTER
+	hex "Data register address of the I2C logging device"
+	help
+	  This an 8-bit data register.
+
+endif # CONSOLE_I2C_SMBUS
+
 config CONSOLE_QEMU_DEBUGCON
 	bool "QEMU debug console output"
 	depends on CPU_QEMU_X86

src/drivers/smbus/Makefile.inc

@@ -0,0 +1,3 @@
+ifeq ($(CONFIG_CONSOLE_I2C_SMBUS),y)
+all-y += i2c_smbus_console.c
+endif

src/drivers/smbus/i2c_smbus_console.c

@@ -0,0 +1,14 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <console/i2c_smbus.h>
+#include <device/smbus_host.h>
+#include <southbridge/intel/bd82x6x/pch.h>
+
+void i2c_smbus_console_init(void) {}
+
+void i2c_smbus_console_tx_byte(unsigned char c)
+{
+	do_smbus_write_byte(CONFIG_FIXED_SMBUS_IO_BASE,
+		CONFIG_CONSOLE_I2C_SMBUS_SLAVE_ADDRESS,
+		CONFIG_CONSOLE_I2C_SMBUS_SLAVE_DATA_REGISTER, c);
+}

src/include/console/i2c_smbus.h

@@ -0,0 +1,28 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#ifndef CONSOLE_I2C_SMBUS_H
+#define CONSOLE_I2C_SMBUS_H
+
+#include <stdint.h>
+
+void i2c_smbus_console_init(void);
+void i2c_smbus_console_tx_byte(unsigned char c);
+
+#define __CONSOLE_SMBUS_ENABLE__	CONFIG(CONSOLE_I2C_SMBUS)
+
+#if __CONSOLE_SMBUS_ENABLE__
+static inline void __i2c_smbus_console_init(void)
+{
+	i2c_smbus_console_init();
+}
+
+static inline void __i2c_smbus_console_tx_byte(u8 data)
+{
+	i2c_smbus_console_tx_byte(data);
+}
+#else
+static inline void __i2c_smbus_console_init(void)	{}
+static inline void __i2c_smbus_console_tx_byte(u8 data)	{}
+#endif /* __CONSOLE_SMBUS_ENABLE__ */
+
+#endif /* CONSOLE_I2C_SMBUS_H */