/*
 * Synopsys DesignWare I2C adapter driver (slave only).
 *
 * Based on the Synopsys DesignWare I2C adapter driver (master).
 *
 * Copyright (C) 2016 Synopsys 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; 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.
 * ----------------------------------------------------------------------------
 *
 */
#include <linux/delay.h>
#include <linux/err.h>
#include <linux/errno.h>
#include <linux/i2c.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/module.h>
#include <linux/pm_runtime.h>

#include "i2c-designware-core.h"

static void i2c_dw_configure_fifo_slave(struct dw_i2c_dev *dev)
{
	/* Configure Tx/Rx FIFO threshold levels. */
	dw_writel(dev, 0, DW_IC_TX_TL);
	dw_writel(dev, 0, DW_IC_RX_TL);

	/* Configure the I2C slave. */
	dw_writel(dev, dev->slave_cfg, DW_IC_CON);
	dw_writel(dev, DW_IC_INTR_SLAVE_MASK, DW_IC_INTR_MASK);
}

/**
 * i2c_dw_init_slave() - Initialize the designware i2c slave hardware
 * @dev: device private data
 *
 * This function configures and enables the I2C in slave mode.
 * This function is called during I2C init function, and in case of timeout at
 * run time.
 */
static int i2c_dw_init_slave(struct dw_i2c_dev *dev)
{
	u32 reg, comp_param1;
	int ret;

	ret = i2c_dw_acquire_lock(dev);
	if (ret)
		return ret;

	reg = dw_readl(dev, DW_IC_COMP_TYPE);
	if (reg == ___constant_swab32(DW_IC_COMP_TYPE_VALUE)) {
		/* Configure register endianness access. */
		dev->flags |= ACCESS_SWAP;
	} else if (reg == (DW_IC_COMP_TYPE_VALUE & 0x0000ffff)) {
		/* Configure register access mode 16bit. */
		dev->flags |= ACCESS_16BIT;
	} else if (reg != DW_IC_COMP_TYPE_VALUE) {
		dev_err(dev->dev,
			"Unknown Synopsys component type: 0x%08x\n", reg);
		i2c_dw_release_lock(dev);
		return -ENODEV;
	}

	comp_param1 = dw_readl(dev, DW_IC_COMP_PARAM_1);

	/* Disable the adapter. */
	__i2c_dw_enable_and_wait(dev, false);

	/* Configure SDA Hold Time if required. */
	reg = dw_readl(dev, DW_IC_COMP_VERSION);
	if (reg >= DW_IC_SDA_HOLD_MIN_VERS) {
		if (!dev->sda_hold_time) {
			/* Keep previous hold time setting if no one set it. */
			dev->sda_hold_time = dw_readl(dev, DW_IC_SDA_HOLD);
		}
		/*
		 * Workaround for avoiding TX arbitration lost in case I2C
		 * slave pulls SDA down "too quickly" after falling egde of
		 * SCL by enabling non-zero SDA RX hold. Specification says it
		 * extends incoming SDA low to high transition while SCL is
		 * high but it apprears to help also above issue.
		 */
		if (!(dev->sda_hold_time & DW_IC_SDA_HOLD_RX_MASK))
			dev->sda_hold_time |= 1 << DW_IC_SDA_HOLD_RX_SHIFT;
		dw_writel(dev, dev->sda_hold_time, DW_IC_SDA_HOLD);
	} else {
		dev_warn(dev->dev,
			 "Hardware too old to adjust SDA hold time.\n");
	}

	i2c_dw_configure_fifo_slave(dev);
	i2c_dw_release_lock(dev);

	return 0;
}

static int i2c_dw_reg_slave(struct i2c_client *slave)
{
	struct dw_i2c_dev *dev = i2c_get_adapdata(slave->adapter);

	if (dev->slave)
		return -EBUSY;
	if (slave->flags & I2C_CLIENT_TEN)
		return -EAFNOSUPPORT;
	pm_runtime_get_sync(dev->dev);

	/*
	 * Set slave address in the IC_SAR register,
	 * the address to which the DW_apb_i2c responds.
	 */
	__i2c_dw_enable(dev, false);
	dw_writel(dev, slave->addr, DW_IC_SAR);
	dev->slave = slave;

	__i2c_dw_enable(dev, true);

	dev->cmd_err = 0;
	dev->msg_write_idx = 0;
	dev->msg_read_idx = 0;
	dev->msg_err = 0;
	dev->status = STATUS_IDLE;
	dev->abort_source = 0;
	dev->rx_outstanding = 0;

	return 0;
}

static int i2c_dw_unreg_slave(struct i2c_client *slave)
{
	struct dw_i2c_dev *dev = i2c_get_adapdata(slave->adapter);

	dev->disable_int(dev);
	dev->disable(dev);
	dev->slave = NULL;
	pm_runtime_put(dev->dev);

	return 0;
}

static u32 i2c_dw_read_clear_intrbits_slave(struct dw_i2c_dev *dev)
{
	u32 stat;

	/*
	 * The IC_INTR_STAT register just indicates "enabled" interrupts.
	 * Ths unmasked raw version of interrupt status bits are available
	 * in the IC_RAW_INTR_STAT register.
	 *
	 * That is,
	 *   stat = dw_readl(IC_INTR_STAT);
	 * equals to,
	 *   stat = dw_readl(IC_RAW_INTR_STAT) & dw_readl(IC_INTR_MASK);
	 *
	 * The raw version might be useful for debugging purposes.
	 */
	stat = dw_readl(dev, DW_IC_INTR_STAT);

	/*
	 * Do not use the IC_CLR_INTR register to clear interrupts, or
	 * you'll miss some interrupts, triggered during the period from
	 * dw_readl(IC_INTR_STAT) to dw_readl(IC_CLR_INTR).
	 *
	 * Instead, use the separately-prepared IC_CLR_* registers.
	 */
	if (stat & DW_IC_INTR_TX_ABRT)
		dw_readl(dev, DW_IC_CLR_TX_ABRT);
	if (stat & DW_IC_INTR_RX_UNDER)
		dw_readl(dev, DW_IC_CLR_RX_UNDER);
	if (stat & DW_IC_INTR_RX_OVER)
		dw_readl(dev, DW_IC_CLR_RX_OVER);
	if (stat & DW_IC_INTR_TX_OVER)
		dw_readl(dev, DW_IC_CLR_TX_OVER);
	if (stat & DW_IC_INTR_RX_DONE)
		dw_readl(dev, DW_IC_CLR_RX_DONE);
	if (stat & DW_IC_INTR_ACTIVITY)
		dw_readl(dev, DW_IC_CLR_ACTIVITY);
	if (stat & DW_IC_INTR_STOP_DET)
		dw_readl(dev, DW_IC_CLR_STOP_DET);
	if (stat & DW_IC_INTR_START_DET)
		dw_readl(dev, DW_IC_CLR_START_DET);
	if (stat & DW_IC_INTR_GEN_CALL)
		dw_readl(dev, DW_IC_CLR_GEN_CALL);

	return stat;
}

/*
 * Interrupt service routine. This gets called whenever an I2C slave interrupt
 * occurs.
 */

static int i2c_dw_irq_handler_slave(struct dw_i2c_dev *dev)
{
	u32 raw_stat, stat, enabled;
	u8 val, slave_activity;

	stat = dw_readl(dev, DW_IC_INTR_STAT);
	enabled = dw_readl(dev, DW_IC_ENABLE);
	raw_stat = dw_readl(dev, DW_IC_RAW_INTR_STAT);
	slave_activity = ((dw_readl(dev, DW_IC_STATUS) &
		DW_IC_STATUS_SLAVE_ACTIVITY) >> 6);

	if (!enabled || !(raw_stat & ~DW_IC_INTR_ACTIVITY) || !dev->slave)
		return 0;

	dev_dbg(dev->dev,
		"%#x STATUS SLAVE_ACTIVITY=%#x : RAW_INTR_STAT=%#x : INTR_STAT=%#x\n",
		enabled, slave_activity, raw_stat, stat);

	if ((stat & DW_IC_INTR_RX_FULL) && (stat & DW_IC_INTR_STOP_DET))
		i2c_slave_event(dev->slave, I2C_SLAVE_WRITE_REQUESTED, &val);

	if (stat & DW_IC_INTR_RD_REQ) {
		if (slave_activity) {
			if (stat & DW_IC_INTR_RX_FULL) {
				val = dw_readl(dev, DW_IC_DATA_CMD);

				if (!i2c_slave_event(dev->slave,
						     I2C_SLAVE_WRITE_RECEIVED,
						     &val)) {
					dev_vdbg(dev->dev, "Byte %X acked!",
						 val);
				}
				dw_readl(dev, DW_IC_CLR_RD_REQ);
				stat = i2c_dw_read_clear_intrbits_slave(dev);
			} else {
				dw_readl(dev, DW_IC_CLR_RD_REQ);
				dw_readl(dev, DW_IC_CLR_RX_UNDER);
				stat = i2c_dw_read_clear_intrbits_slave(dev);
			}
			if (!i2c_slave_event(dev->slave,
					     I2C_SLAVE_READ_REQUESTED,
					     &val))
				dw_writel(dev, val, DW_IC_DATA_CMD);
		}
	}

	if (stat & DW_IC_INTR_RX_DONE) {
		if (!i2c_slave_event(dev->slave, I2C_SLAVE_READ_PROCESSED,
				     &val))
			dw_readl(dev, DW_IC_CLR_RX_DONE);

		i2c_slave_event(dev->slave, I2C_SLAVE_STOP, &val);
		stat = i2c_dw_read_clear_intrbits_slave(dev);
		return 1;
	}

	if (stat & DW_IC_INTR_RX_FULL) {
		val = dw_readl(dev, DW_IC_DATA_CMD);
		if (!i2c_slave_event(dev->slave, I2C_SLAVE_WRITE_RECEIVED,
				     &val))
			dev_vdbg(dev->dev, "Byte %X acked!", val);
	} else {
		i2c_slave_event(dev->slave, I2C_SLAVE_STOP, &val);
		stat = i2c_dw_read_clear_intrbits_slave(dev);
	}

	return 1;
}

static irqreturn_t i2c_dw_isr_slave(int this_irq, void *dev_id)
{
	struct dw_i2c_dev *dev = dev_id;
	int ret;

	i2c_dw_read_clear_intrbits_slave(dev);
	ret = i2c_dw_irq_handler_slave(dev);
	if (ret > 0)
		complete(&dev->cmd_complete);

	return IRQ_RETVAL(ret);
}

static const struct i2c_algorithm i2c_dw_algo = {
	.functionality = i2c_dw_func,
	.reg_slave = i2c_dw_reg_slave,
	.unreg_slave = i2c_dw_unreg_slave,
};

int i2c_dw_probe_slave(struct dw_i2c_dev *dev)
{
	struct i2c_adapter *adap = &dev->adapter;
	int ret;

	init_completion(&dev->cmd_complete);

	dev->init = i2c_dw_init_slave;
	dev->disable = i2c_dw_disable;
	dev->disable_int = i2c_dw_disable_int;

	ret = dev->init(dev);
	if (ret)
		return ret;

	snprintf(adap->name, sizeof(adap->name),
		 "Synopsys DesignWare I2C Slave adapter");
	adap->retries = 3;
	adap->algo = &i2c_dw_algo;
	adap->dev.parent = dev->dev;
	i2c_set_adapdata(adap, dev);

	ret = devm_request_irq(dev->dev, dev->irq, i2c_dw_isr_slave,
			       IRQF_SHARED, dev_name(dev->dev), dev);
	if (ret) {
		dev_err(dev->dev, "failure requesting irq %i: %d\n",
			dev->irq, ret);
		return ret;
	}

	ret = i2c_add_numbered_adapter(adap);
	if (ret)
		dev_err(dev->dev, "failure adding adapter: %d\n", ret);

	return ret;
}
EXPORT_SYMBOL_GPL(i2c_dw_probe_slave);

MODULE_AUTHOR("Luis Oliveira <lolivei@synopsys.com>");
MODULE_DESCRIPTION("Synopsys DesignWare I2C bus slave adapter");
MODULE_LICENSE("GPL v2");