/*
   * 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/err.h>
  #include <linux/platform_device.h>
  #include <linux/hw_random.h>
  #include <linux/delay.h>
  #include <linux/slab.h>
  #include <linux/pm_runtime.h>
  #include <linux/of.h>
  #include <linux/of_device.h>
  #include <linux/of_address.h>
  #include <linux/interrupt.h>
  
  #include <asm/io.h>
  
  #define RNG_REG_STATUS_RDY			(1 << 0)
  
  #define RNG_REG_INTACK_RDY_MASK			(1 << 0)
  #define RNG_REG_INTACK_SHUTDOWN_OFLO_MASK	(1 << 1)
  #define RNG_SHUTDOWN_OFLO_MASK			(1 << 1)
  
  #define RNG_CONTROL_STARTUP_CYCLES_SHIFT	16
  #define RNG_CONTROL_STARTUP_CYCLES_MASK		(0xffff << 16)
  #define RNG_CONTROL_ENABLE_TRNG_SHIFT		10
  #define RNG_CONTROL_ENABLE_TRNG_MASK		(1 << 10)
  
  #define RNG_CONFIG_MAX_REFIL_CYCLES_SHIFT	16
  #define RNG_CONFIG_MAX_REFIL_CYCLES_MASK	(0xffff << 16)
  #define RNG_CONFIG_MIN_REFIL_CYCLES_SHIFT	0
  #define RNG_CONFIG_MIN_REFIL_CYCLES_MASK	(0xff << 0)
  
  #define RNG_CONTROL_STARTUP_CYCLES		0xff
  #define RNG_CONFIG_MIN_REFIL_CYCLES		0x21
  #define RNG_CONFIG_MAX_REFIL_CYCLES		0x22
  
  #define RNG_ALARMCNT_ALARM_TH_SHIFT		0x0
  #define RNG_ALARMCNT_ALARM_TH_MASK		(0xff << 0)
  #define RNG_ALARMCNT_SHUTDOWN_TH_SHIFT		16
  #define RNG_ALARMCNT_SHUTDOWN_TH_MASK		(0x1f << 16)
  #define RNG_ALARM_THRESHOLD			0xff
  #define RNG_SHUTDOWN_THRESHOLD			0x4
  
  #define RNG_REG_FROENABLE_MASK			0xffffff
  #define RNG_REG_FRODETUNE_MASK			0xffffff
  
  #define OMAP2_RNG_OUTPUT_SIZE			0x4
  #define OMAP4_RNG_OUTPUT_SIZE			0x8
  
  enum {
  	RNG_OUTPUT_L_REG = 0,
  	RNG_OUTPUT_H_REG,
  	RNG_STATUS_REG,
  	RNG_INTMASK_REG,
  	RNG_INTACK_REG,
  	RNG_CONTROL_REG,
  	RNG_CONFIG_REG,
  	RNG_ALARMCNT_REG,
  	RNG_FROENABLE_REG,
  	RNG_FRODETUNE_REG,
  	RNG_ALARMMASK_REG,
  	RNG_ALARMSTOP_REG,
  	RNG_REV_REG,
  	RNG_SYSCONFIG_REG,
  };
  
  static const u16 reg_map_omap2[] = {
  	[RNG_OUTPUT_L_REG]	= 0x0,
  	[RNG_STATUS_REG]	= 0x4,
  	[RNG_CONFIG_REG]	= 0x28,
  	[RNG_REV_REG]		= 0x3c,
  	[RNG_SYSCONFIG_REG]	= 0x40,
  };
  
  static const u16 reg_map_omap4[] = {
  	[RNG_OUTPUT_L_REG]	= 0x0,
  	[RNG_OUTPUT_H_REG]	= 0x4,
  	[RNG_STATUS_REG]	= 0x8,
  	[RNG_INTMASK_REG]	= 0xc,
  	[RNG_INTACK_REG]	= 0x10,
  	[RNG_CONTROL_REG]	= 0x14,
  	[RNG_CONFIG_REG]	= 0x18,
  	[RNG_ALARMCNT_REG]	= 0x1c,
  	[RNG_FROENABLE_REG]	= 0x20,
  	[RNG_FRODETUNE_REG]	= 0x24,
  	[RNG_ALARMMASK_REG]	= 0x28,
  	[RNG_ALARMSTOP_REG]	= 0x2c,
  	[RNG_REV_REG]		= 0x1FE0,
  	[RNG_SYSCONFIG_REG]	= 0x1FE4,
  };
  
  struct omap_rng_dev;
  /**
   * struct omap_rng_pdata - RNG IP block-specific data
   * @regs: Pointer to the register offsets structure.
   * @data_size: No. of bytes in RNG output.
   * @data_present: Callback to determine if data is available.
   * @init: Callback for IP specific initialization sequence.
   * @cleanup: Callback for IP specific cleanup sequence.
   */
  struct omap_rng_pdata {
  	u16	*regs;
  	u32	data_size;
  	u32	(*data_present)(struct omap_rng_dev *priv);
  	int	(*init)(struct omap_rng_dev *priv);
  	void	(*cleanup)(struct omap_rng_dev *priv);
  };
  
  struct omap_rng_dev {
  	void __iomem			*base;
  	struct device			*dev;
  	const struct omap_rng_pdata	*pdata;
  };
  
  static inline u32 omap_rng_read(struct omap_rng_dev *priv, u16 reg)
  {
  	return __raw_readl(priv->base + priv->pdata->regs[reg]);
  }
  
  static inline void omap_rng_write(struct omap_rng_dev *priv, u16 reg,
  				      u32 val)
  {
  	__raw_writel(val, priv->base + priv->pdata->regs[reg]);
  }
  
  static int omap_rng_data_present(struct hwrng *rng, int wait)
  {
  	struct omap_rng_dev *priv;
  	int data, i;
  
  	priv = (struct omap_rng_dev *)rng->priv;
  
  	for (i = 0; i < 20; i++) {
  		data = priv->pdata->data_present(priv);
  		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)
  {
  	struct omap_rng_dev *priv;
  	u32 data_size, i;
  
  	priv = (struct omap_rng_dev *)rng->priv;
  	data_size = priv->pdata->data_size;
  
  	for (i = 0; i < data_size / sizeof(u32); i++)
  		data[i] = omap_rng_read(priv, RNG_OUTPUT_L_REG + i);
  
  	if (priv->pdata->regs[RNG_INTACK_REG])
  		omap_rng_write(priv, RNG_INTACK_REG, RNG_REG_INTACK_RDY_MASK);
  	return data_size;
  }
  
  static int omap_rng_init(struct hwrng *rng)
  {
  	struct omap_rng_dev *priv;
  
  	priv = (struct omap_rng_dev *)rng->priv;
  	return priv->pdata->init(priv);
  }
  
  static void omap_rng_cleanup(struct hwrng *rng)
  {
  	struct omap_rng_dev *priv;
  
  	priv = (struct omap_rng_dev *)rng->priv;
  	priv->pdata->cleanup(priv);
  }
  
  static struct hwrng omap_rng_ops = {
  	.name		= "omap",
  	.data_present	= omap_rng_data_present,
  	.data_read	= omap_rng_data_read,
  	.init		= omap_rng_init,
  	.cleanup	= omap_rng_cleanup,
  };
  
  static inline u32 omap2_rng_data_present(struct omap_rng_dev *priv)
  {
  	return omap_rng_read(priv, RNG_STATUS_REG) ? 0 : 1;
  }
  
  static int omap2_rng_init(struct omap_rng_dev *priv)
  {
  	omap_rng_write(priv, RNG_SYSCONFIG_REG, 0x1);
  	return 0;
  }
  
  static void omap2_rng_cleanup(struct omap_rng_dev *priv)
  {
  	omap_rng_write(priv, RNG_SYSCONFIG_REG, 0x0);
  }
  
  static struct omap_rng_pdata omap2_rng_pdata = {
  	.regs		= (u16 *)reg_map_omap2,
  	.data_size	= OMAP2_RNG_OUTPUT_SIZE,
  	.data_present	= omap2_rng_data_present,
  	.init		= omap2_rng_init,
  	.cleanup	= omap2_rng_cleanup,
  };
  
  #if defined(CONFIG_OF)
  static inline u32 omap4_rng_data_present(struct omap_rng_dev *priv)
  {
  	return omap_rng_read(priv, RNG_STATUS_REG) & RNG_REG_STATUS_RDY;
  }
  
  static int omap4_rng_init(struct omap_rng_dev *priv)
  {
  	u32 val;
  
  	/* Return if RNG is already running. */
  	if (omap_rng_read(priv, RNG_CONTROL_REG) & RNG_CONTROL_ENABLE_TRNG_MASK)
  		return 0;
  
  	val = RNG_CONFIG_MIN_REFIL_CYCLES << RNG_CONFIG_MIN_REFIL_CYCLES_SHIFT;
  	val |= RNG_CONFIG_MAX_REFIL_CYCLES << RNG_CONFIG_MAX_REFIL_CYCLES_SHIFT;
  	omap_rng_write(priv, RNG_CONFIG_REG, val);
  
  	omap_rng_write(priv, RNG_FRODETUNE_REG, 0x0);
  	omap_rng_write(priv, RNG_FROENABLE_REG, RNG_REG_FROENABLE_MASK);
  	val = RNG_ALARM_THRESHOLD << RNG_ALARMCNT_ALARM_TH_SHIFT;
  	val |= RNG_SHUTDOWN_THRESHOLD << RNG_ALARMCNT_SHUTDOWN_TH_SHIFT;
  	omap_rng_write(priv, RNG_ALARMCNT_REG, val);
  
  	val = RNG_CONTROL_STARTUP_CYCLES << RNG_CONTROL_STARTUP_CYCLES_SHIFT;
  	val |= RNG_CONTROL_ENABLE_TRNG_MASK;
  	omap_rng_write(priv, RNG_CONTROL_REG, val);
  
  	return 0;
  }
  
  static void omap4_rng_cleanup(struct omap_rng_dev *priv)
  {
  	int val;
  
  	val = omap_rng_read(priv, RNG_CONTROL_REG);
  	val &= ~RNG_CONTROL_ENABLE_TRNG_MASK;
  	omap_rng_write(priv, RNG_CONTROL_REG, val);
  }
  
  static irqreturn_t omap4_rng_irq(int irq, void *dev_id)
  {
  	struct omap_rng_dev *priv = dev_id;
  	u32 fro_detune, fro_enable;
  
  	/*
  	 * Interrupt raised by a fro shutdown threshold, do the following:
  	 * 1. Clear the alarm events.
  	 * 2. De tune the FROs which are shutdown.
  	 * 3. Re enable the shutdown FROs.
  	 */
  	omap_rng_write(priv, RNG_ALARMMASK_REG, 0x0);
  	omap_rng_write(priv, RNG_ALARMSTOP_REG, 0x0);
  
  	fro_enable = omap_rng_read(priv, RNG_FROENABLE_REG);
  	fro_detune = ~fro_enable & RNG_REG_FRODETUNE_MASK;
  	fro_detune = fro_detune | omap_rng_read(priv, RNG_FRODETUNE_REG);
  	fro_enable = RNG_REG_FROENABLE_MASK;
  
  	omap_rng_write(priv, RNG_FRODETUNE_REG, fro_detune);
  	omap_rng_write(priv, RNG_FROENABLE_REG, fro_enable);
  
  	omap_rng_write(priv, RNG_INTACK_REG, RNG_REG_INTACK_SHUTDOWN_OFLO_MASK);
  
  	return IRQ_HANDLED;
  }
  
  static struct omap_rng_pdata omap4_rng_pdata = {
  	.regs		= (u16 *)reg_map_omap4,
  	.data_size	= OMAP4_RNG_OUTPUT_SIZE,
  	.data_present	= omap4_rng_data_present,
  	.init		= omap4_rng_init,
  	.cleanup	= omap4_rng_cleanup,
  };
  
  static const struct of_device_id omap_rng_of_match[] = {
  		{
  			.compatible	= "ti,omap2-rng",
  			.data		= &omap2_rng_pdata,
  		},
  		{
  			.compatible	= "ti,omap4-rng",
  			.data		= &omap4_rng_pdata,
  		},
  		{},
  };
  MODULE_DEVICE_TABLE(of, omap_rng_of_match);
  
  static int of_get_omap_rng_device_details(struct omap_rng_dev *priv,
  					  struct platform_device *pdev)
  {
  	const struct of_device_id *match;
  	struct device *dev = &pdev->dev;
  	int irq, err;
  
  	match = of_match_device(of_match_ptr(omap_rng_of_match), dev);
  	if (!match) {
  		dev_err(dev, "no compatible OF match
  ");
  		return -EINVAL;
  	}
  	priv->pdata = match->data;
  
  	if (of_device_is_compatible(dev->of_node, "ti,omap4-rng")) {
  		irq = platform_get_irq(pdev, 0);
  		if (irq < 0) {
  			dev_err(dev, "%s: error getting IRQ resource - %d
  ",
  				__func__, irq);
  			return irq;
  		}
  
  		err = devm_request_irq(dev, irq, omap4_rng_irq,
  				       IRQF_TRIGGER_NONE, dev_name(dev), priv);
  		if (err) {
  			dev_err(dev, "unable to request irq %d, err = %d
  ",
  				irq, err);
  			return err;
  		}
  		omap_rng_write(priv, RNG_INTMASK_REG, RNG_SHUTDOWN_OFLO_MASK);
  	}
  	return 0;
  }
  #else
  static int of_get_omap_rng_device_details(struct omap_rng_dev *omap_rng,
  					  struct platform_device *pdev)
  {
  	return -EINVAL;
  }
  #endif
  
  static int get_omap_rng_device_details(struct omap_rng_dev *omap_rng)
  {
  	/* Only OMAP2/3 can be non-DT */
  	omap_rng->pdata = &omap2_rng_pdata;
  	return 0;
  }
  
  static int omap_rng_probe(struct platform_device *pdev)
  {
  	struct omap_rng_dev *priv;
  	struct resource *res;
  	struct device *dev = &pdev->dev;
  	int ret;
  
  	priv = devm_kzalloc(dev, sizeof(struct omap_rng_dev), GFP_KERNEL);
  	if (!priv)
  		return -ENOMEM;
  
  	omap_rng_ops.priv = (unsigned long)priv;
  	platform_set_drvdata(pdev, priv);
  	priv->dev = dev;
  
  	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
  	priv->base = devm_ioremap_resource(dev, res);
  	if (IS_ERR(priv->base)) {
  		ret = PTR_ERR(priv->base);
  		goto err_ioremap;
  	}
  
  	pm_runtime_enable(&pdev->dev);
  	ret = pm_runtime_get_sync(&pdev->dev);
  	if (ret < 0) {
  		dev_err(&pdev->dev, "Failed to runtime_get device: %d
  ", ret);
  		pm_runtime_put_noidle(&pdev->dev);
  		goto err_ioremap;
  	}
  
  	ret = (dev->of_node) ? of_get_omap_rng_device_details(priv, pdev) :
  				get_omap_rng_device_details(priv);
  	if (ret)
  		goto err_ioremap;
  
  	ret = hwrng_register(&omap_rng_ops);
  	if (ret)
  		goto err_register;
  
  	dev_info(&pdev->dev, "OMAP Random Number Generator ver. %02x
  ",
  		 omap_rng_read(priv, RNG_REV_REG));
  
  	return 0;
  
  err_register:
  	priv->base = NULL;
  	pm_runtime_disable(&pdev->dev);
  err_ioremap:
  	dev_err(dev, "initialization failed.
  ");
  	return ret;
  }
  
  static int omap_rng_remove(struct platform_device *pdev)
  {
  	struct omap_rng_dev *priv = platform_get_drvdata(pdev);
  
  	hwrng_unregister(&omap_rng_ops);
  
  	priv->pdata->cleanup(priv);
  
  	pm_runtime_put_sync(&pdev->dev);
  	pm_runtime_disable(&pdev->dev);
  
  	return 0;
  }
  
  static int __maybe_unused omap_rng_suspend(struct device *dev)
  {
  	struct omap_rng_dev *priv = dev_get_drvdata(dev);
  
  	priv->pdata->cleanup(priv);
  	pm_runtime_put_sync(dev);
  
  	return 0;
  }
  
  static int __maybe_unused omap_rng_resume(struct device *dev)
  {
  	struct omap_rng_dev *priv = dev_get_drvdata(dev);
  	int ret;
  
  	ret = pm_runtime_get_sync(dev);
  	if (ret < 0) {
  		dev_err(dev, "Failed to runtime_get device: %d
  ", ret);
  		pm_runtime_put_noidle(dev);
  		return ret;
  	}
  
  	priv->pdata->init(priv);
  
  	return 0;
  }
  
  static SIMPLE_DEV_PM_OPS(omap_rng_pm, omap_rng_suspend, omap_rng_resume);
  
  static struct platform_driver omap_rng_driver = {
  	.driver = {
  		.name		= "omap_rng",
  		.pm		= &omap_rng_pm,
  		.of_match_table = of_match_ptr(omap_rng_of_match),
  	},
  	.probe		= omap_rng_probe,
  	.remove		= omap_rng_remove,
  };
  
  module_platform_driver(omap_rng_driver);
  MODULE_ALIAS("platform:omap_rng");
  MODULE_AUTHOR("Deepak Saxena (and others)");
  MODULE_LICENSE("GPL");