/*
   * S3C2416/2450 CPUfreq Support
   *
   * Copyright 2011 Heiko Stuebner <heiko@sntech.de>
   *
   * based on s3c64xx_cpufreq.c
   *
   * Copyright 2009 Wolfson Microelectronics plc
   *
   * 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.
   */
  
  #include <linux/kernel.h>
  #include <linux/types.h>
  #include <linux/init.h>
  #include <linux/cpufreq.h>
  #include <linux/clk.h>
  #include <linux/err.h>
  #include <linux/regulator/consumer.h>
  #include <linux/reboot.h>
  #include <linux/module.h>
  
  static DEFINE_MUTEX(cpufreq_lock);
  
  struct s3c2416_data {
  	struct clk *armdiv;
  	struct clk *armclk;
  	struct clk *hclk;
  
  	unsigned long regulator_latency;
  #ifdef CONFIG_ARM_S3C2416_CPUFREQ_VCORESCALE
  	struct regulator *vddarm;
  #endif
  
  	struct cpufreq_frequency_table *freq_table;
  
  	bool is_dvs;
  	bool disable_dvs;
  };
  
  static struct s3c2416_data s3c2416_cpufreq;
  
  struct s3c2416_dvfs {
  	unsigned int vddarm_min;
  	unsigned int vddarm_max;
  };
  
  /* pseudo-frequency for dvs mode */
  #define FREQ_DVS	132333
  
  /* frequency to sleep and reboot in
   * it's essential to leave dvs, as some boards do not reconfigure the
   * regulator on reboot
   */
  #define FREQ_SLEEP	133333
  
  /* Sources for the ARMCLK */
  #define SOURCE_HCLK	0
  #define SOURCE_ARMDIV	1
  
  #ifdef CONFIG_ARM_S3C2416_CPUFREQ_VCORESCALE
  /* S3C2416 only supports changing the voltage in the dvs-mode.
   * Voltages down to 1.0V seem to work, so we take what the regulator
   * can get us.
   */
  static struct s3c2416_dvfs s3c2416_dvfs_table[] = {
  	[SOURCE_HCLK] = {  950000, 1250000 },
  	[SOURCE_ARMDIV] = { 1250000, 1350000 },
  };
  #endif
  
  static struct cpufreq_frequency_table s3c2416_freq_table[] = {
  	{ SOURCE_HCLK, FREQ_DVS },
  	{ SOURCE_ARMDIV, 133333 },
  	{ SOURCE_ARMDIV, 266666 },
  	{ SOURCE_ARMDIV, 400000 },
  	{ 0, CPUFREQ_TABLE_END },
  };
  
  static struct cpufreq_frequency_table s3c2450_freq_table[] = {
  	{ SOURCE_HCLK, FREQ_DVS },
  	{ SOURCE_ARMDIV, 133500 },
  	{ SOURCE_ARMDIV, 267000 },
  	{ SOURCE_ARMDIV, 534000 },
  	{ 0, CPUFREQ_TABLE_END },
  };
  
  static unsigned int s3c2416_cpufreq_get_speed(unsigned int cpu)
  {
  	struct s3c2416_data *s3c_freq = &s3c2416_cpufreq;
  
  	if (cpu != 0)
  		return 0;
  
  	/* return our pseudo-frequency when in dvs mode */
  	if (s3c_freq->is_dvs)
  		return FREQ_DVS;
  
  	return clk_get_rate(s3c_freq->armclk) / 1000;
  }
  
  static int s3c2416_cpufreq_set_armdiv(struct s3c2416_data *s3c_freq,
  				      unsigned int freq)
  {
  	int ret;
  
  	if (clk_get_rate(s3c_freq->armdiv) / 1000 != freq) {
  		ret = clk_set_rate(s3c_freq->armdiv, freq * 1000);
  		if (ret < 0) {
  			pr_err("cpufreq: Failed to set armdiv rate %dkHz: %d
  ",
  			       freq, ret);
  			return ret;
  		}
  	}
  
  	return 0;
  }
  
  static int s3c2416_cpufreq_enter_dvs(struct s3c2416_data *s3c_freq, int idx)
  {
  #ifdef CONFIG_ARM_S3C2416_CPUFREQ_VCORESCALE
  	struct s3c2416_dvfs *dvfs;
  #endif
  	int ret;
  
  	if (s3c_freq->is_dvs) {
  		pr_debug("cpufreq: already in dvs mode, nothing to do
  ");
  		return 0;
  	}
  
  	pr_debug("cpufreq: switching armclk to hclk (%lukHz)
  ",
  		 clk_get_rate(s3c_freq->hclk) / 1000);
  	ret = clk_set_parent(s3c_freq->armclk, s3c_freq->hclk);
  	if (ret < 0) {
  		pr_err("cpufreq: Failed to switch armclk to hclk: %d
  ", ret);
  		return ret;
  	}
  
  #ifdef CONFIG_ARM_S3C2416_CPUFREQ_VCORESCALE
  	/* changing the core voltage is only allowed when in dvs mode */
  	if (s3c_freq->vddarm) {
  		dvfs = &s3c2416_dvfs_table[idx];
  
  		pr_debug("cpufreq: setting regulator to %d-%d
  ",
  			 dvfs->vddarm_min, dvfs->vddarm_max);
  		ret = regulator_set_voltage(s3c_freq->vddarm,
  					    dvfs->vddarm_min,
  					    dvfs->vddarm_max);
  
  		/* when lowering the voltage failed, there is nothing to do */
  		if (ret != 0)
  			pr_err("cpufreq: Failed to set VDDARM: %d
  ", ret);
  	}
  #endif
  
  	s3c_freq->is_dvs = 1;
  
  	return 0;
  }
  
  static int s3c2416_cpufreq_leave_dvs(struct s3c2416_data *s3c_freq, int idx)
  {
  #ifdef CONFIG_ARM_S3C2416_CPUFREQ_VCORESCALE
  	struct s3c2416_dvfs *dvfs;
  #endif
  	int ret;
  
  	if (!s3c_freq->is_dvs) {
  		pr_debug("cpufreq: not in dvs mode, so can't leave
  ");
  		return 0;
  	}
  
  #ifdef CONFIG_ARM_S3C2416_CPUFREQ_VCORESCALE
  	if (s3c_freq->vddarm) {
  		dvfs = &s3c2416_dvfs_table[idx];
  
  		pr_debug("cpufreq: setting regulator to %d-%d
  ",
  			 dvfs->vddarm_min, dvfs->vddarm_max);
  		ret = regulator_set_voltage(s3c_freq->vddarm,
  					    dvfs->vddarm_min,
  					    dvfs->vddarm_max);
  		if (ret != 0) {
  			pr_err("cpufreq: Failed to set VDDARM: %d
  ", ret);
  			return ret;
  		}
  	}
  #endif
  
  	/* force armdiv to hclk frequency for transition from dvs*/
  	if (clk_get_rate(s3c_freq->armdiv) > clk_get_rate(s3c_freq->hclk)) {
  		pr_debug("cpufreq: force armdiv to hclk frequency (%lukHz)
  ",
  			 clk_get_rate(s3c_freq->hclk) / 1000);
  		ret = s3c2416_cpufreq_set_armdiv(s3c_freq,
  					clk_get_rate(s3c_freq->hclk) / 1000);
  		if (ret < 0) {
  			pr_err("cpufreq: Failed to set the armdiv to %lukHz: %d
  ",
  			       clk_get_rate(s3c_freq->hclk) / 1000, ret);
  			return ret;
  		}
  	}
  
  	pr_debug("cpufreq: switching armclk parent to armdiv (%lukHz)
  ",
  			clk_get_rate(s3c_freq->armdiv) / 1000);
  
  	ret = clk_set_parent(s3c_freq->armclk, s3c_freq->armdiv);
  	if (ret < 0) {
  		pr_err("cpufreq: Failed to switch armclk clock parent to armdiv: %d
  ",
  		       ret);
  		return ret;
  	}
  
  	s3c_freq->is_dvs = 0;
  
  	return 0;
  }
  
  static int s3c2416_cpufreq_set_target(struct cpufreq_policy *policy,
  				      unsigned int index)
  {
  	struct s3c2416_data *s3c_freq = &s3c2416_cpufreq;
  	unsigned int new_freq;
  	int idx, ret, to_dvs = 0;
  
  	mutex_lock(&cpufreq_lock);
  
  	idx = s3c_freq->freq_table[index].driver_data;
  
  	if (idx == SOURCE_HCLK)
  		to_dvs = 1;
  
  	/* switching to dvs when it's not allowed */
  	if (to_dvs && s3c_freq->disable_dvs) {
  		pr_debug("cpufreq: entering dvs mode not allowed
  ");
  		ret = -EINVAL;
  		goto out;
  	}
  
  	/* When leavin dvs mode, always switch the armdiv to the hclk rate
  	 * The S3C2416 has stability issues when switching directly to
  	 * higher frequencies.
  	 */
  	new_freq = (s3c_freq->is_dvs && !to_dvs)
  				? clk_get_rate(s3c_freq->hclk) / 1000
  				: s3c_freq->freq_table[index].frequency;
  
  	if (to_dvs) {
  		pr_debug("cpufreq: enter dvs
  ");
  		ret = s3c2416_cpufreq_enter_dvs(s3c_freq, idx);
  	} else if (s3c_freq->is_dvs) {
  		pr_debug("cpufreq: leave dvs
  ");
  		ret = s3c2416_cpufreq_leave_dvs(s3c_freq, idx);
  	} else {
  		pr_debug("cpufreq: change armdiv to %dkHz
  ", new_freq);
  		ret = s3c2416_cpufreq_set_armdiv(s3c_freq, new_freq);
  	}
  
  out:
  	mutex_unlock(&cpufreq_lock);
  
  	return ret;
  }
  
  #ifdef CONFIG_ARM_S3C2416_CPUFREQ_VCORESCALE
  static void __init s3c2416_cpufreq_cfg_regulator(struct s3c2416_data *s3c_freq)
  {
  	int count, v, i, found;
  	struct cpufreq_frequency_table *freq;
  	struct s3c2416_dvfs *dvfs;
  
  	count = regulator_count_voltages(s3c_freq->vddarm);
  	if (count < 0) {
  		pr_err("cpufreq: Unable to check supported voltages
  ");
  		return;
  	}
  
  	freq = s3c_freq->freq_table;
  	while (count > 0 && freq->frequency != CPUFREQ_TABLE_END) {
  		if (freq->frequency == CPUFREQ_ENTRY_INVALID)
  			continue;
  
  		dvfs = &s3c2416_dvfs_table[freq->driver_data];
  		found = 0;
  
  		/* Check only the min-voltage, more is always ok on S3C2416 */
  		for (i = 0; i < count; i++) {
  			v = regulator_list_voltage(s3c_freq->vddarm, i);
  			if (v >= dvfs->vddarm_min)
  				found = 1;
  		}
  
  		if (!found) {
  			pr_debug("cpufreq: %dkHz unsupported by regulator
  ",
  				 freq->frequency);
  			freq->frequency = CPUFREQ_ENTRY_INVALID;
  		}
  
  		freq++;
  	}
  
  	/* Guessed */
  	s3c_freq->regulator_latency = 1 * 1000 * 1000;
  }
  #endif
  
  static int s3c2416_cpufreq_reboot_notifier_evt(struct notifier_block *this,
  					       unsigned long event, void *ptr)
  {
  	struct s3c2416_data *s3c_freq = &s3c2416_cpufreq;
  	int ret;
  
  	mutex_lock(&cpufreq_lock);
  
  	/* disable further changes */
  	s3c_freq->disable_dvs = 1;
  
  	mutex_unlock(&cpufreq_lock);
  
  	/* some boards don't reconfigure the regulator on reboot, which
  	 * could lead to undervolting the cpu when the clock is reset.
  	 * Therefore we always leave the DVS mode on reboot.
  	 */
  	if (s3c_freq->is_dvs) {
  		pr_debug("cpufreq: leave dvs on reboot
  ");
  		ret = cpufreq_driver_target(cpufreq_cpu_get(0), FREQ_SLEEP, 0);
  		if (ret < 0)
  			return NOTIFY_BAD;
  	}
  
  	return NOTIFY_DONE;
  }
  
  static struct notifier_block s3c2416_cpufreq_reboot_notifier = {
  	.notifier_call = s3c2416_cpufreq_reboot_notifier_evt,
  };
  
  static int __init s3c2416_cpufreq_driver_init(struct cpufreq_policy *policy)
  {
  	struct s3c2416_data *s3c_freq = &s3c2416_cpufreq;
  	struct cpufreq_frequency_table *freq;
  	struct clk *msysclk;
  	unsigned long rate;
  	int ret;
  
  	if (policy->cpu != 0)
  		return -EINVAL;
  
  	msysclk = clk_get(NULL, "msysclk");
  	if (IS_ERR(msysclk)) {
  		ret = PTR_ERR(msysclk);
  		pr_err("cpufreq: Unable to obtain msysclk: %d
  ", ret);
  		return ret;
  	}
  
  	/*
  	 * S3C2416 and S3C2450 share the same processor-ID and also provide no
  	 * other means to distinguish them other than through the rate of
  	 * msysclk. On S3C2416 msysclk runs at 800MHz and on S3C2450 at 533MHz.
  	 */
  	rate = clk_get_rate(msysclk);
  	if (rate == 800 * 1000 * 1000) {
  		pr_info("cpufreq: msysclk running at %lukHz, using S3C2416 frequency table
  ",
  			rate / 1000);
  		s3c_freq->freq_table = s3c2416_freq_table;
  		policy->cpuinfo.max_freq = 400000;
  	} else if (rate / 1000 == 534000) {
  		pr_info("cpufreq: msysclk running at %lukHz, using S3C2450 frequency table
  ",
  			rate / 1000);
  		s3c_freq->freq_table = s3c2450_freq_table;
  		policy->cpuinfo.max_freq = 534000;
  	}
  
  	/* not needed anymore */
  	clk_put(msysclk);
  
  	if (s3c_freq->freq_table == NULL) {
  		pr_err("cpufreq: No frequency information for this CPU, msysclk at %lukHz
  ",
  		       rate / 1000);
  		return -ENODEV;
  	}
  
  	s3c_freq->is_dvs = 0;
  
  	s3c_freq->armdiv = clk_get(NULL, "armdiv");
  	if (IS_ERR(s3c_freq->armdiv)) {
  		ret = PTR_ERR(s3c_freq->armdiv);
  		pr_err("cpufreq: Unable to obtain ARMDIV: %d
  ", ret);
  		return ret;
  	}
  
  	s3c_freq->hclk = clk_get(NULL, "hclk");
  	if (IS_ERR(s3c_freq->hclk)) {
  		ret = PTR_ERR(s3c_freq->hclk);
  		pr_err("cpufreq: Unable to obtain HCLK: %d
  ", ret);
  		goto err_hclk;
  	}
  
  	/* chech hclk rate, we only support the common 133MHz for now
  	 * hclk could also run at 66MHz, but this not often used
  	 */
  	rate = clk_get_rate(s3c_freq->hclk);
  	if (rate < 133 * 1000 * 1000) {
  		pr_err("cpufreq: HCLK not at 133MHz
  ");
  		clk_put(s3c_freq->hclk);
  		ret = -EINVAL;
  		goto err_armclk;
  	}
  
  	s3c_freq->armclk = clk_get(NULL, "armclk");
  	if (IS_ERR(s3c_freq->armclk)) {
  		ret = PTR_ERR(s3c_freq->armclk);
  		pr_err("cpufreq: Unable to obtain ARMCLK: %d
  ", ret);
  		goto err_armclk;
  	}
  
  #ifdef CONFIG_ARM_S3C2416_CPUFREQ_VCORESCALE
  	s3c_freq->vddarm = regulator_get(NULL, "vddarm");
  	if (IS_ERR(s3c_freq->vddarm)) {
  		ret = PTR_ERR(s3c_freq->vddarm);
  		pr_err("cpufreq: Failed to obtain VDDARM: %d
  ", ret);
  		goto err_vddarm;
  	}
  
  	s3c2416_cpufreq_cfg_regulator(s3c_freq);
  #else
  	s3c_freq->regulator_latency = 0;
  #endif
  
  	freq = s3c_freq->freq_table;
  	while (freq->frequency != CPUFREQ_TABLE_END) {
  		/* special handling for dvs mode */
  		if (freq->driver_data == 0) {
  			if (!s3c_freq->hclk) {
  				pr_debug("cpufreq: %dkHz unsupported as it would need unavailable dvs mode
  ",
  					 freq->frequency);
  				freq->frequency = CPUFREQ_ENTRY_INVALID;
  			} else {
  				freq++;
  				continue;
  			}
  		}
  
  		/* Check for frequencies we can generate */
  		rate = clk_round_rate(s3c_freq->armdiv,
  				      freq->frequency * 1000);
  		rate /= 1000;
  		if (rate != freq->frequency) {
  			pr_debug("cpufreq: %dkHz unsupported by clock (clk_round_rate return %lu)
  ",
  				 freq->frequency, rate);
  			freq->frequency = CPUFREQ_ENTRY_INVALID;
  		}
  
  		freq++;
  	}
  
  	/* Datasheet says PLL stabalisation time must be at least 300us,
  	 * so but add some fudge. (reference in LOCKCON0 register description)
  	 */
  	ret = cpufreq_generic_init(policy, s3c_freq->freq_table,
  			(500 * 1000) + s3c_freq->regulator_latency);
  	if (ret)
  		goto err_freq_table;
  
  	register_reboot_notifier(&s3c2416_cpufreq_reboot_notifier);
  
  	return 0;
  
  err_freq_table:
  #ifdef CONFIG_ARM_S3C2416_CPUFREQ_VCORESCALE
  	regulator_put(s3c_freq->vddarm);
  err_vddarm:
  #endif
  	clk_put(s3c_freq->armclk);
  err_armclk:
  	clk_put(s3c_freq->hclk);
  err_hclk:
  	clk_put(s3c_freq->armdiv);
  
  	return ret;
  }
  
  static struct cpufreq_driver s3c2416_cpufreq_driver = {
  	.flags		= CPUFREQ_NEED_INITIAL_FREQ_CHECK,
  	.verify		= cpufreq_generic_frequency_table_verify,
  	.target_index	= s3c2416_cpufreq_set_target,
  	.get		= s3c2416_cpufreq_get_speed,
  	.init		= s3c2416_cpufreq_driver_init,
  	.name		= "s3c2416",
  	.attr		= cpufreq_generic_attr,
  };
  
  static int __init s3c2416_cpufreq_init(void)
  {
  	return cpufreq_register_driver(&s3c2416_cpufreq_driver);
  }
  module_init(s3c2416_cpufreq_init);