text: /*
   * Driver for Atmel Flexcom
   *
   * Copyright (C) 2015 Atmel Corporation
   *
   * Author: Cyrille Pitchen <cyrille.pitchen@atmel.com>
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License version 2 as
   * published by the Free Software Foundation.
   *
   * 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.  If not, see <http://www.gnu.org/licenses/>.
   */
  
  #include <linux/module.h>
  #include <linux/types.h>
  #include <linux/kernel.h>
  #include <linux/platform_device.h>
  #include <linux/of.h>
  #include <linux/of_platform.h>
  #include <linux/err.h>
  #include <linux/io.h>
  #include <linux/clk.h>
  #include <dt-bindings/mfd/atmel-flexcom.h>
  
  /* I/O register offsets */
  #define FLEX_MR		0x0	/* Mode Register */
  #define FLEX_VERSION	0xfc	/* Version Register */
  
  /* Mode Register bit fields */
  #define FLEX_MR_OPMODE_OFFSET	(0)  /* Operating Mode */
  #define FLEX_MR_OPMODE_MASK	(0x3 << FLEX_MR_OPMODE_OFFSET)
  #define FLEX_MR_OPMODE(opmode)	(((opmode) << FLEX_MR_OPMODE_OFFSET) &	\
  				 FLEX_MR_OPMODE_MASK)
  
  struct atmel_flexcom {
  	void __iomem *base;
  	u32 opmode;
  	struct clk *clk;
  };
  
  static int atmel_flexcom_probe(struct platform_device *pdev)
  {
  	struct device_node *np = pdev->dev.of_node;
  	struct resource *res;
  	struct atmel_flexcom *ddata;
  	int err;
  
  	ddata = devm_kzalloc(&pdev->dev, sizeof(*ddata), GFP_KERNEL);
  	if (!ddata)
  		return -ENOMEM;
  
  	platform_set_drvdata(pdev, ddata);
  
  	err = of_property_read_u32(np, "atmel,flexcom-mode", &ddata->opmode);
  	if (err)
  		return err;
  
  	if (ddata->opmode < ATMEL_FLEXCOM_MODE_USART ||
  	    ddata->opmode > ATMEL_FLEXCOM_MODE_TWI)
  		return -EINVAL;
  
  	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
  	ddata->base = devm_ioremap_resource(&pdev->dev, res);
  	if (IS_ERR(ddata->base))
  		return PTR_ERR(ddata->base);
  
  	ddata->clk = devm_clk_get(&pdev->dev, NULL);
  	if (IS_ERR(ddata->clk))
  		return PTR_ERR(ddata->clk);
  
  	err = clk_prepare_enable(ddata->clk);
  	if (err)
  		return err;
  
  	/*
  	 * Set the Operating Mode in the Mode Register: only the selected device
  	 * is clocked. Hence, registers of the other serial devices remain
  	 * inaccessible and are read as zero. Also the external I/O lines of the
  	 * Flexcom are muxed to reach the selected device.
  	 */
  	writel(FLEX_MR_OPMODE(ddata->opmode), ddata->base + FLEX_MR);
  
  	clk_disable_unprepare(ddata->clk);
  
  	return devm_of_platform_populate(&pdev->dev);
  }
  
  static const struct of_device_id atmel_flexcom_of_match[] = {
  	{ .compatible = "atmel,sama5d2-flexcom" },
  	{ /* sentinel */ }
  };
  MODULE_DEVICE_TABLE(of, atmel_flexcom_of_match);
  
  #ifdef CONFIG_PM_SLEEP
  static int atmel_flexcom_resume(struct device *dev)
  {
  	struct atmel_flexcom *ddata = dev_get_drvdata(dev);
  	int err;
  	u32 val;
  
  	err = clk_prepare_enable(ddata->clk);
  	if (err)
  		return err;
  
  	val = FLEX_MR_OPMODE(ddata->opmode),
  	writel(val, ddata->base + FLEX_MR);
  
  	clk_disable_unprepare(ddata->clk);
  
  	return 0;
  }
  #endif
  
  static SIMPLE_DEV_PM_OPS(atmel_flexcom_pm_ops, NULL,
  			 atmel_flexcom_resume);
  
  static struct platform_driver atmel_flexcom_driver = {
  	.probe	= atmel_flexcom_probe,
  	.driver	= {
  		.name		= "atmel_flexcom",
  		.pm		= &atmel_flexcom_pm_ops,
  		.of_match_table	= atmel_flexcom_of_match,
  	},
  };
  
  module_platform_driver(atmel_flexcom_driver);
  
  MODULE_AUTHOR("Cyrille Pitchen <cyrille.pitchen@atmel.com>");
  MODULE_DESCRIPTION("Atmel Flexcom MFD driver");
  MODULE_LICENSE("GPL v2");
  