text: // SPDX-License-Identifier: GPL-2.0
  /*
   * Synopsys DesignWare I2C adapter driver (slave only).
   *
   * Based on the Synopsys DesignWare I2C adapter driver (master).
   *
   * Copyright (C) 2016 Synopsys Inc.
   */
  #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 <linux/regmap.h>
  
  #include "i2c-designware-core.h"
  
  static void i2c_dw_configure_fifo_slave(struct dw_i2c_dev *dev)
  {
  	/* Configure Tx/Rx FIFO threshold levels. */
  	regmap_write(dev->map, DW_IC_TX_TL, 0);
  	regmap_write(dev->map, DW_IC_RX_TL, 0);
  
  	/* Configure the I2C slave. */
  	regmap_write(dev->map, DW_IC_CON, dev->slave_cfg);
  	regmap_write(dev->map, DW_IC_INTR_MASK, DW_IC_INTR_SLAVE_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)
  {
  	int ret;
  
  	ret = i2c_dw_acquire_lock(dev);
  	if (ret)
  		return ret;
  
  	/* Disable the adapter. */
  	__i2c_dw_disable(dev);
  
  	/* Write SDA hold time if supported */
  	if (dev->sda_hold_time)
  		regmap_write(dev->map, DW_IC_SDA_HOLD, dev->sda_hold_time);
  
  	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_disable_nowait(dev);
  	regmap_write(dev->map, DW_IC_SAR, slave->addr);
  	dev->slave = slave;
  
  	__i2c_dw_enable(dev);
  
  	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);
  	synchronize_irq(dev->irq);
  	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, dummy;
  
  	/*
  	 * The IC_INTR_STAT register just indicates "enabled" interrupts.
  	 * The unmasked raw version of interrupt status bits is available
  	 * in the IC_RAW_INTR_STAT register.
  	 *
  	 * That is,
  	 *   stat = readl(IC_INTR_STAT);
  	 * equals to,
  	 *   stat = readl(IC_RAW_INTR_STAT) & readl(IC_INTR_MASK);
  	 *
  	 * The raw version might be useful for debugging purposes.
  	 */
  	regmap_read(dev->map, DW_IC_INTR_STAT, &stat);
  
  	/*
  	 * Do not use the IC_CLR_INTR register to clear interrupts, or
  	 * you'll miss some interrupts, triggered during the period from
  	 * readl(IC_INTR_STAT) to readl(IC_CLR_INTR).
  	 *
  	 * Instead, use the separately-prepared IC_CLR_* registers.
  	 */
  	if (stat & DW_IC_INTR_TX_ABRT)
  		regmap_read(dev->map, DW_IC_CLR_TX_ABRT, &dummy);
  	if (stat & DW_IC_INTR_RX_UNDER)
  		regmap_read(dev->map, DW_IC_CLR_RX_UNDER, &dummy);
  	if (stat & DW_IC_INTR_RX_OVER)
  		regmap_read(dev->map, DW_IC_CLR_RX_OVER, &dummy);
  	if (stat & DW_IC_INTR_TX_OVER)
  		regmap_read(dev->map, DW_IC_CLR_TX_OVER, &dummy);
  	if (stat & DW_IC_INTR_RX_DONE)
  		regmap_read(dev->map, DW_IC_CLR_RX_DONE, &dummy);
  	if (stat & DW_IC_INTR_ACTIVITY)
  		regmap_read(dev->map, DW_IC_CLR_ACTIVITY, &dummy);
  	if (stat & DW_IC_INTR_STOP_DET)
  		regmap_read(dev->map, DW_IC_CLR_STOP_DET, &dummy);
  	if (stat & DW_IC_INTR_START_DET)
  		regmap_read(dev->map, DW_IC_CLR_START_DET, &dummy);
  	if (stat & DW_IC_INTR_GEN_CALL)
  		regmap_read(dev->map, DW_IC_CLR_GEN_CALL, &dummy);
  
  	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, tmp;
  	u8 val = 0, slave_activity;
  
  	regmap_read(dev->map, DW_IC_INTR_STAT, &stat);
  	regmap_read(dev->map, DW_IC_ENABLE, &enabled);
  	regmap_read(dev->map, DW_IC_RAW_INTR_STAT, &raw_stat);
  	regmap_read(dev->map, DW_IC_STATUS, &tmp);
  	slave_activity = ((tmp & 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) {
  				regmap_read(dev->map, DW_IC_DATA_CMD, &tmp);
  				val = tmp;
  
  				if (!i2c_slave_event(dev->slave,
  						     I2C_SLAVE_WRITE_RECEIVED,
  						     &val)) {
  					dev_vdbg(dev->dev, "Byte %X acked!",
  						 val);
  				}
  				regmap_read(dev->map, DW_IC_CLR_RD_REQ, &tmp);
  				stat = i2c_dw_read_clear_intrbits_slave(dev);
  			} else {
  				regmap_read(dev->map, DW_IC_CLR_RD_REQ, &tmp);
  				regmap_read(dev->map, DW_IC_CLR_RX_UNDER, &tmp);
  				stat = i2c_dw_read_clear_intrbits_slave(dev);
  			}
  			if (!i2c_slave_event(dev->slave,
  					     I2C_SLAVE_READ_REQUESTED,
  					     &val))
  				regmap_write(dev->map, DW_IC_DATA_CMD, val);
  		}
  	}
  
  	if (stat & DW_IC_INTR_RX_DONE) {
  		if (!i2c_slave_event(dev->slave, I2C_SLAVE_READ_PROCESSED,
  				     &val))
  			regmap_read(dev->map, DW_IC_CLR_RX_DONE, &tmp);
  
  		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) {
  		regmap_read(dev->map, DW_IC_DATA_CMD, &tmp);
  		val = tmp;
  		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,
  };
  
  void i2c_dw_configure_slave(struct dw_i2c_dev *dev)
  {
  	dev->functionality = I2C_FUNC_SLAVE | DW_IC_DEFAULT_FUNCTIONALITY;
  
  	dev->slave_cfg = DW_IC_CON_RX_FIFO_FULL_HLD_CTRL |
  			 DW_IC_CON_RESTART_EN | DW_IC_CON_STOP_DET_IFADDRESSED;
  
  	dev->mode = DW_IC_SLAVE;
  }
  EXPORT_SYMBOL_GPL(i2c_dw_configure_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 = i2c_dw_init_regmap(dev);
  	if (ret)
  		return ret;
  
  	ret = i2c_dw_set_sda_hold(dev);
  	if (ret)
  		return ret;
  
  	ret = i2c_dw_set_fifo_size(dev);
  	if (ret)
  		return ret;
  
  	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");
  