text: /*
   * omap-rng.c - RNG driver for TI OMAP CPU family
   *
   * Author: Deepak Saxena <dsaxena@plexity.net>
   *
   * Copyright 2005 (c) MontaVista Software, Inc.
   *
   * Mostly based on original driver:
   *
   * Copyright (C) 2005 Nokia Corporation
   * Author: Juha Yrjölä <juha.yrjola@nokia.com>
   *
   * This file is licensed under  the terms of the GNU General Public
   * License version 2. This program is licensed "as is" without any
   * warranty of any kind, whether express or implied.
   */
  
  #include <linux/module.h>
  #include <linux/init.h>
  #include <linux/random.h>
  #include <linux/clk.h>
  #include <linux/err.h>
  #include <linux/platform_device.h>
  #include <linux/hw_random.h>
  #include <linux/delay.h>
  
  #include <asm/io.h>
  
  #define RNG_OUT_REG		0x00		/* Output register */
  #define RNG_STAT_REG		0x04		/* Status register
  							[0] = STAT_BUSY */
  #define RNG_ALARM_REG		0x24		/* Alarm register
  							[7:0] = ALARM_COUNTER */
  #define RNG_CONFIG_REG		0x28		/* Configuration register
  							[11:6] = RESET_COUNT
  							[5:3]  = RING2_DELAY
  							[2:0]  = RING1_DELAY */
  #define RNG_REV_REG		0x3c		/* Revision register
  							[7:0] = REV_NB */
  #define RNG_MASK_REG		0x40		/* Mask and reset register
  							[2] = IT_EN
  							[1] = SOFTRESET
  							[0] = AUTOIDLE */
  #define RNG_SYSSTATUS		0x44		/* System status
  							[0] = RESETDONE */
  
  static void __iomem *rng_base;
  static struct clk *rng_ick;
  static struct platform_device *rng_dev;
  
  static inline u32 omap_rng_read_reg(int reg)
  {
  	return __raw_readl(rng_base + reg);
  }
  
  static inline void omap_rng_write_reg(int reg, u32 val)
  {
  	__raw_writel(val, rng_base + reg);
  }
  
  static int omap_rng_data_present(struct hwrng *rng, int wait)
  {
  	int data, i;
  
  	for (i = 0; i < 20; i++) {
  		data = omap_rng_read_reg(RNG_STAT_REG) ? 0 : 1;
  		if (data || !wait)
  			break;
  		/* RNG produces data fast enough (2+ MBit/sec, even
  		 * during "rngtest" loads, that these delays don't
  		 * seem to trigger.  We *could* use the RNG IRQ, but
  		 * that'd be higher overhead ... so why bother?
  		 */
  		udelay(10);
  	}
  	return data;
  }
  
  static int omap_rng_data_read(struct hwrng *rng, u32 *data)
  {
  	*data = omap_rng_read_reg(RNG_OUT_REG);
  
  	return 4;
  }
  
  static struct hwrng omap_rng_ops = {
  	.name		= "omap",
  	.data_present	= omap_rng_data_present,
  	.data_read	= omap_rng_data_read,
  };
  
  static int __devinit omap_rng_probe(struct platform_device *pdev)
  {
  	struct resource *res;
  	int ret;
  
  	/*
  	 * A bit ugly, and it will never actually happen but there can
  	 * be only one RNG and this catches any bork
  	 */
  	if (rng_dev)
  		return -EBUSY;
  
  	if (cpu_is_omap24xx()) {
  		rng_ick = clk_get(&pdev->dev, "ick");
  		if (IS_ERR(rng_ick)) {
  			dev_err(&pdev->dev, "Could not get rng_ick\n");
  			ret = PTR_ERR(rng_ick);
  			return ret;
  		} else
  			clk_enable(rng_ick);
  	}
  
  	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
  
  	if (!res) {
  		ret = -ENOENT;
  		goto err_region;
  	}
  
  	if (!request_mem_region(res->start, resource_size(res), pdev->name)) {
  		ret = -EBUSY;
  		goto err_region;
  	}
  
  	dev_set_drvdata(&pdev->dev, res);
  	rng_base = ioremap(res->start, resource_size(res));
  	if (!rng_base) {
  		ret = -ENOMEM;
  		goto err_ioremap;
  	}
  
  	ret = hwrng_register(&omap_rng_ops);
  	if (ret)
  		goto err_register;
  
  	dev_info(&pdev->dev, "OMAP Random Number Generator ver. %02x\n",
  		omap_rng_read_reg(RNG_REV_REG));
  	omap_rng_write_reg(RNG_MASK_REG, 0x1);
  
  	rng_dev = pdev;
  
  	return 0;
  
  err_register:
  	iounmap(rng_base);
  	rng_base = NULL;
  err_ioremap:
  	release_mem_region(res->start, resource_size(res));
  err_region:
  	if (cpu_is_omap24xx()) {
  		clk_disable(rng_ick);
  		clk_put(rng_ick);
  	}
  	return ret;
  }
  
  static int __exit omap_rng_remove(struct platform_device *pdev)
  {
  	struct resource *res = dev_get_drvdata(&pdev->dev);
  
  	hwrng_unregister(&omap_rng_ops);
  
  	omap_rng_write_reg(RNG_MASK_REG, 0x0);
  
  	iounmap(rng_base);
  
  	if (cpu_is_omap24xx()) {
  		clk_disable(rng_ick);
  		clk_put(rng_ick);
  	}
  
  	release_mem_region(res->start, resource_size(res));
  	rng_base = NULL;
  
  	return 0;
  }
  
  #ifdef CONFIG_PM
  
  static int omap_rng_suspend(struct platform_device *pdev, pm_message_t message)
  {
  	omap_rng_write_reg(RNG_MASK_REG, 0x0);
  	return 0;
  }
  
  static int omap_rng_resume(struct platform_device *pdev)
  {
  	omap_rng_write_reg(RNG_MASK_REG, 0x1);
  	return 0;
  }
  
  #else
  
  #define	omap_rng_suspend	NULL
  #define	omap_rng_resume		NULL
  
  #endif
  
  /* work with hotplug and coldplug */
  MODULE_ALIAS("platform:omap_rng");
  
  static struct platform_driver omap_rng_driver = {
  	.driver = {
  		.name		= "omap_rng",
  		.owner		= THIS_MODULE,
  	},
  	.probe		= omap_rng_probe,
  	.remove		= __exit_p(omap_rng_remove),
  	.suspend	= omap_rng_suspend,
  	.resume		= omap_rng_resume
  };
  
  static int __init omap_rng_init(void)
  {
  	if (!cpu_is_omap16xx() && !cpu_is_omap24xx())
  		return -ENODEV;
  
  	return platform_driver_register(&omap_rng_driver);
  }
  
  static void __exit omap_rng_exit(void)
  {
  	platform_driver_unregister(&omap_rng_driver);
  }
  
  module_init(omap_rng_init);
  module_exit(omap_rng_exit);
  
  MODULE_AUTHOR("Deepak Saxena (and others)");
  MODULE_LICENSE("GPL");
  