driver/usb_mux_ps874x.c

/* Copyright 2017 The Chromium OS Authors. All rights reserved.
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 *
 * Parade PS874X USB Type-C Redriving Switch for USB Host / DisplayPort.
 */

#include "common.h"
#include "i2c.h"
#include "usb_mux_ps874x.h"
#include "usb_mux.h"
#include "util.h"

static inline int ps874x_read(int i2c_addr, uint8_t reg, int *val)
{
	return i2c_read8(I2C_PORT_USB_MUX, i2c_addr, reg, val);
}

static inline int ps874x_write(int i2c_addr, uint8_t reg, uint8_t val)
{
	return i2c_write8(I2C_PORT_USB_MUX, i2c_addr, reg, val);
}

static int ps874x_init(int i2c_addr)
{
	int val;
	int res;

	/* Reset chip back to power-on state */
	res = ps874x_write(i2c_addr, PS874X_REG_MODE, PS874X_MODE_POWER_DOWN);
	if (res)
		return res;

	/*
	 * Verify revision / chip ID registers.
	 * From Parade: PS8743 may have REVISION_ID1 as 0 or 1,
	 * PS8740 may have REVISION_ID2 as 0 or 1,
	 * 1 is derived from 0 and have same functionality.
	 */
	res = ps874x_read(i2c_addr, PS874X_REG_REVISION_ID1, &val);
	if (res)
		return res;
	if (val < PS874X_REVISION_ID1)
		return EC_ERROR_UNKNOWN;

	res = ps874x_read(i2c_addr, PS874X_REG_REVISION_ID2, &val);
	if (res)
		return res;
	if (val < PS874X_REVISION_ID2)
		return EC_ERROR_UNKNOWN;

	res = ps874x_read(i2c_addr, PS874X_REG_CHIP_ID1, &val);
	if (res)
		return res;
	if (val != PS874X_CHIP_ID1)
		return EC_ERROR_UNKNOWN;

	res  = ps874x_read(i2c_addr, PS874X_REG_CHIP_ID2, &val);
	if (res)
		return res;
	if (val != PS874X_CHIP_ID2)
		return EC_ERROR_UNKNOWN;

	return EC_SUCCESS;
}

/* Writes control register to set switch mode */
static int ps874x_set_mux(int i2c_addr, mux_state_t mux_state)
{
	uint8_t reg = 0;

	if (mux_state & MUX_USB_ENABLED)
		reg |= PS874X_MODE_USB_ENABLED;
	if (mux_state & MUX_DP_ENABLED)
		reg |= PS874X_MODE_DP_ENABLED;
	if (mux_state & MUX_POLARITY_INVERTED)
		reg |= PS874X_MODE_POLARITY_INVERTED;

	return ps874x_write(i2c_addr, PS874X_REG_MODE, reg);
}

/* Reads control register and updates mux_state accordingly */
static int ps874x_get_mux(int i2c_addr, mux_state_t *mux_state)
{
	int reg;
	int res;

	res = ps874x_read(i2c_addr, PS874X_REG_STATUS, &reg);
	if (res)
		return res;

	*mux_state = 0;
	if (reg & PS874X_STATUS_USB_ENABLED)
		*mux_state |= MUX_USB_ENABLED;
	if (reg & PS874X_STATUS_DP_ENABLED)
		*mux_state |= MUX_DP_ENABLED;
	if (reg & PS874X_STATUS_POLARITY_INVERTED)
		*mux_state |= MUX_POLARITY_INVERTED;

	return EC_SUCCESS;
}

/* Tune USB Tx/Rx Equalization */
int ps874x_tune_usb_eq(int i2c_addr, uint8_t tx, uint8_t rx)
{
	int ret;

	ret = ps874x_write(i2c_addr, PS874X_REG_USB_EQ_TX, tx);
	ret |= ps874x_write(i2c_addr, PS874X_REG_USB_EQ_RX, rx);

	return ret;
}

const struct usb_mux_driver ps874x_usb_mux_driver = {
	.init = ps874x_init,
	.set = ps874x_set_mux,
	.get = ps874x_get_mux,
};