src/soc/intel/common/lpss_i2c.h

/*
 * This file is part of the coreboot project.
 *
 * Copyright 2016 Google Inc.
 *
 * 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; version 2 of the License.
 *
 * 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.
 */

#ifndef SOC_INTEL_COMMON_LPSS_I2C_H
#define SOC_INTEL_COMMON_LPSS_I2C_H

#include <device/i2c.h>
#include <stdint.h>

/*
 * Timing values are in units of clock period, with the clock speed
 * provided by the SOC in CONFIG_SOC_INTEL_COMMON_LPSS_I2C_CLOCK_MHZ.
 * Automatic configuration is done based on requested speed, but the
 * values may need tuned depending on the board and the number of
 * devices present on the bus.
 */
struct lpss_i2c_speed_config {
	enum i2c_speed speed;
	/* SCL high and low period count */
	uint16_t scl_lcnt;
	uint16_t scl_hcnt;
	/*
	 * SDA hold time should be 300ns in standard and fast modes
	 * and long enough for deterministic logic level change in
	 * fast-plus and high speed modes.
	 *
	 *  [15:0] SDA TX Hold Time
	 * [23:16] SDA RX Hold Time
	 */
	uint32_t sda_hold;
};

/*
 * This I2C controller has support for 3 independent speed configs but can
 * support both FAST_PLUS and HIGH speeds through the same set of speed
 * config registers.  These are treated separately so the speed config values
 * can be provided via ACPI to the OS.
 */
#define LPSS_I2C_SPEED_CONFIG_COUNT	4

struct lpss_i2c_bus_config {
	/* Bus should be enabled prior to ramstage with temporary base */
	int early_init;
	/* Bus speed in Hz, default is I2C_SPEED_FAST (400 KHz) */
	enum i2c_speed speed;
	/* If rise_time_ns is non-zero the calculations for lcnt and hcnt
	 * registers take into account the times of the bus. However, if
	 * there is a match in speed_config those register values take
	 * precedence. */
	int rise_time_ns;
	int fall_time_ns;
	/* Specific bus speed configuration */
	struct lpss_i2c_speed_config speed_config[LPSS_I2C_SPEED_CONFIG_COUNT];
};

#define LPSS_I2C_SPEED_CONFIG(speedval,lcnt,hcnt,hold)	\
	{						\
		.speed = I2C_SPEED_ ## speedval,	\
		.scl_lcnt = (lcnt),			\
		.scl_hcnt = (hcnt),			\
		.sda_hold = (hold),			\
	}

/*
 * Return the base address for this bus controller.
 *
 * This function *must* be implemented by the SOC and return the appropriate
 * base address for the I2C registers that correspond to the provided bus.
 */
uintptr_t lpss_i2c_base_address(unsigned bus);

/*
 * Generate I2C timing information into the SSDT for the OS driver to consume,
 * optionally applying override values provided by the caller.
 */
void lpss_i2c_acpi_fill_ssdt(unsigned bus,
				const struct lpss_i2c_bus_config *bcfg);

/*
 * Initialize this bus controller and set the speed.
 *
 * The bus speed can be passed in Hz or using values from device/i2c.h and
 * will default to I2C_SPEED_FAST if it is not provided.
 *
 * The SOC *must* define CONFIG_SOC_INTEL_COMMON_LPSS_I2C_CLOCK for the
 * bus speed calculation to be correct.
 */
int lpss_i2c_init(unsigned bus, const struct lpss_i2c_bus_config *bcfg);

#endif