/*
   * IBM OPAL I2C driver
   * Copyright (C) 2014 IBM
   *
   * 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.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program.
   */
  
  #include <linux/device.h>
  #include <linux/i2c.h>
  #include <linux/kernel.h>
  #include <linux/mm.h>
  #include <linux/module.h>
  #include <linux/of.h>
  #include <linux/platform_device.h>
  #include <linux/slab.h>
  
  #include <asm/firmware.h>
  #include <asm/opal.h>
  
  static int i2c_opal_translate_error(int rc)
  {
  	switch (rc) {
  	case OPAL_NO_MEM:
  		return -ENOMEM;
  	case OPAL_PARAMETER:
  		return -EINVAL;
  	case OPAL_I2C_ARBT_LOST:
  		return -EAGAIN;
  	case OPAL_I2C_TIMEOUT:
  		return -ETIMEDOUT;
  	case OPAL_I2C_NACK_RCVD:
  		return -ENXIO;
  	case OPAL_I2C_STOP_ERR:
  		return -EBUSY;
  	default:
  		return -EIO;
  	}
  }
  
  static int i2c_opal_send_request(u32 bus_id, struct opal_i2c_request *req)
  {
  	struct opal_msg msg;
  	int token, rc;
  
  	token = opal_async_get_token_interruptible();
  	if (token < 0) {
  		if (token != -ERESTARTSYS)
  			pr_err("Failed to get the async token
  ");
  
  		return token;
  	}
  
  	rc = opal_i2c_request(token, bus_id, req);
  	if (rc != OPAL_ASYNC_COMPLETION) {
  		rc = i2c_opal_translate_error(rc);
  		goto exit;
  	}
  
  	rc = opal_async_wait_response(token, &msg);
  	if (rc)
  		goto exit;
  
  	rc = be64_to_cpu(msg.params[1]);
  	if (rc != OPAL_SUCCESS) {
  		rc = i2c_opal_translate_error(rc);
  		goto exit;
  	}
  
  exit:
  	opal_async_release_token(token);
  	return rc;
  }
  
  static int i2c_opal_master_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
  				int num)
  {
  	unsigned long opal_id = (unsigned long)adap->algo_data;
  	struct opal_i2c_request req;
  	int rc, i;
  
  	/* We only support fairly simple combinations here of one
  	 * or two messages
  	 */
  	memset(&req, 0, sizeof(req));
  	switch(num) {
  	case 0:
  		return 0;
  	case 1:
  		req.type = (msgs[0].flags & I2C_M_RD) ?
  			OPAL_I2C_RAW_READ : OPAL_I2C_RAW_WRITE;
  		req.addr = cpu_to_be16(msgs[0].addr);
  		req.size = cpu_to_be32(msgs[0].len);
  		req.buffer_ra = cpu_to_be64(__pa(msgs[0].buf));
  		break;
  	case 2:
  		req.type = (msgs[1].flags & I2C_M_RD) ?
  			OPAL_I2C_SM_READ : OPAL_I2C_SM_WRITE;
  		req.addr = cpu_to_be16(msgs[0].addr);
  		req.subaddr_sz = msgs[0].len;
  		for (i = 0; i < msgs[0].len; i++)
  			req.subaddr = (req.subaddr << 8) | msgs[0].buf[i];
  		req.subaddr = cpu_to_be32(req.subaddr);
  		req.size = cpu_to_be32(msgs[1].len);
  		req.buffer_ra = cpu_to_be64(__pa(msgs[1].buf));
  		break;
  	default:
  		return -EOPNOTSUPP;
  	}
  
  	rc = i2c_opal_send_request(opal_id, &req);
  	if (rc)
  		return rc;
  
  	return num;
  }
  
  static int i2c_opal_smbus_xfer(struct i2c_adapter *adap, u16 addr,
  			       unsigned short flags, char read_write,
  			       u8 command, int size, union i2c_smbus_data *data)
  {
  	unsigned long opal_id = (unsigned long)adap->algo_data;
  	struct opal_i2c_request req;
  	u8 local[2];
  	int rc;
  
  	memset(&req, 0, sizeof(req));
  
  	req.addr = cpu_to_be16(addr);
  	switch (size) {
  	case I2C_SMBUS_BYTE:
  		req.buffer_ra = cpu_to_be64(__pa(&data->byte));
  		req.size = cpu_to_be32(1);
  		/* Fall through */
  	case I2C_SMBUS_QUICK:
  		req.type = (read_write == I2C_SMBUS_READ) ?
  			OPAL_I2C_RAW_READ : OPAL_I2C_RAW_WRITE;
  		break;
  	case I2C_SMBUS_BYTE_DATA:
  		req.buffer_ra = cpu_to_be64(__pa(&data->byte));
  		req.size = cpu_to_be32(1);
  		req.subaddr = cpu_to_be32(command);
  		req.subaddr_sz = 1;
  		req.type = (read_write == I2C_SMBUS_READ) ?
  			OPAL_I2C_SM_READ : OPAL_I2C_SM_WRITE;
  		break;
  	case I2C_SMBUS_WORD_DATA:
  		if (!read_write) {
  			local[0] = data->word & 0xff;
  			local[1] = (data->word >> 8) & 0xff;
  		}
  		req.buffer_ra = cpu_to_be64(__pa(local));
  		req.size = cpu_to_be32(2);
  		req.subaddr = cpu_to_be32(command);
  		req.subaddr_sz = 1;
  		req.type = (read_write == I2C_SMBUS_READ) ?
  			OPAL_I2C_SM_READ : OPAL_I2C_SM_WRITE;
  		break;
  	case I2C_SMBUS_I2C_BLOCK_DATA:
  		req.buffer_ra = cpu_to_be64(__pa(&data->block[1]));
  		req.size = cpu_to_be32(data->block[0]);
  		req.subaddr = cpu_to_be32(command);
  		req.subaddr_sz = 1;
  		req.type = (read_write == I2C_SMBUS_READ) ?
  			OPAL_I2C_SM_READ : OPAL_I2C_SM_WRITE;
  		break;
  	default:
  		return -EINVAL;
  	}
  
  	rc = i2c_opal_send_request(opal_id, &req);
  	if (!rc && read_write && size == I2C_SMBUS_WORD_DATA) {
  		data->word = ((u16)local[1]) << 8;
  		data->word |= local[0];
  	}
  
  	return rc;
  }
  
  static u32 i2c_opal_func(struct i2c_adapter *adapter)
  {
  	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_QUICK | I2C_FUNC_SMBUS_BYTE |
  	       I2C_FUNC_SMBUS_BYTE_DATA | I2C_FUNC_SMBUS_WORD_DATA |
  	       I2C_FUNC_SMBUS_I2C_BLOCK;
  }
  
  static const struct i2c_algorithm i2c_opal_algo = {
  	.master_xfer	= i2c_opal_master_xfer,
  	.smbus_xfer	= i2c_opal_smbus_xfer,
  	.functionality	= i2c_opal_func,
  };
  
  /*
   * For two messages, we basically support simple smbus transactions of a
   * write-then-anything.
   */
  static struct i2c_adapter_quirks i2c_opal_quirks = {
  	.flags = I2C_AQ_COMB | I2C_AQ_COMB_WRITE_FIRST | I2C_AQ_COMB_SAME_ADDR,
  	.max_comb_1st_msg_len = 4,
  };
  
  static int i2c_opal_probe(struct platform_device *pdev)
  {
  	struct i2c_adapter	*adapter;
  	const char		*pname;
  	u32			opal_id;
  	int			rc;
  
  	if (!pdev->dev.of_node)
  		return -ENODEV;
  
  	rc = of_property_read_u32(pdev->dev.of_node, "ibm,opal-id", &opal_id);
  	if (rc) {
  		dev_err(&pdev->dev, "Missing ibm,opal-id property !
  ");
  		return -EIO;
  	}
  
  	adapter = devm_kzalloc(&pdev->dev, sizeof(*adapter), GFP_KERNEL);
  	if (!adapter)
  		return -ENOMEM;
  
  	adapter->algo = &i2c_opal_algo;
  	adapter->algo_data = (void *)(unsigned long)opal_id;
  	adapter->quirks = &i2c_opal_quirks;
  	adapter->dev.parent = &pdev->dev;
  	adapter->dev.of_node = of_node_get(pdev->dev.of_node);
  	pname = of_get_property(pdev->dev.of_node, "ibm,port-name", NULL);
  	if (pname)
  		strlcpy(adapter->name, pname, sizeof(adapter->name));
  	else
  		strlcpy(adapter->name, "opal", sizeof(adapter->name));
  
  	platform_set_drvdata(pdev, adapter);
  	rc = i2c_add_adapter(adapter);
  	if (rc)
  		dev_err(&pdev->dev, "Failed to register the i2c adapter
  ");
  
  	return rc;
  }
  
  static int i2c_opal_remove(struct platform_device *pdev)
  {
  	struct i2c_adapter *adapter = platform_get_drvdata(pdev);
  
  	i2c_del_adapter(adapter);
  
  	return 0;
  }
  
  static const struct of_device_id i2c_opal_of_match[] = {
  	{
  		.compatible = "ibm,opal-i2c",
  	},
  	{ }
  };
  MODULE_DEVICE_TABLE(of, i2c_opal_of_match);
  
  static struct platform_driver i2c_opal_driver = {
  	.probe	= i2c_opal_probe,
  	.remove	= i2c_opal_remove,
  	.driver	= {
  		.name		= "i2c-opal",
  		.of_match_table	= i2c_opal_of_match,
  	},
  };
  
  static int __init i2c_opal_init(void)
  {
  	if (!firmware_has_feature(FW_FEATURE_OPAL))
  		return -ENODEV;
  
  	return platform_driver_register(&i2c_opal_driver);
  }
  module_init(i2c_opal_init);
  
  static void __exit i2c_opal_exit(void)
  {
  	return platform_driver_unregister(&i2c_opal_driver);
  }
  module_exit(i2c_opal_exit);
  
  MODULE_AUTHOR("Neelesh Gupta <neelegup@linux.vnet.ibm.com>");
  MODULE_DESCRIPTION("IBM OPAL I2C driver");
  MODULE_LICENSE("GPL");