/*
   * drivers/cpufreq/spear-cpufreq.c
   *
   * CPU Frequency Scaling for SPEAr platform
   *
   * Copyright (C) 2012 ST Microelectronics
   * Deepak Sikri <deepak.sikri@st.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.
   */
  
  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  
  #include <linux/clk.h>
  #include <linux/cpufreq.h>
  #include <linux/err.h>
  #include <linux/init.h>
  #include <linux/module.h>

  #include <linux/of_device.h>

  #include <linux/platform_device.h>

  #include <linux/slab.h>
  #include <linux/types.h>
  
  /* SPEAr CPUFreq driver data structure */
  static struct {
  	struct clk *clk;
  	unsigned int transition_latency;
  	struct cpufreq_frequency_table *freq_tbl;
  	u32 cnt;
  } spear_cpufreq;

  static struct clk *spear1340_cpu_get_possible_parent(unsigned long newfreq)
  {
  	struct clk *sys_pclk;
  	int pclk;
  	/*
  	 * In SPEAr1340, cpu clk's parent sys clk can take input from
  	 * following sources
  	 */
  	const char *sys_clk_src[] = {
  		"sys_syn_clk",
  		"pll1_clk",
  		"pll2_clk",
  		"pll3_clk",
  	};
  
  	/*
  	 * As sys clk can have multiple source with their own range
  	 * limitation so we choose possible sources accordingly
  	 */
  	if (newfreq <= 300000000)
  		pclk = 0; /* src is sys_syn_clk */
  	else if (newfreq > 300000000 && newfreq <= 500000000)
  		pclk = 3; /* src is pll3_clk */
  	else if (newfreq == 600000000)
  		pclk = 1; /* src is pll1_clk */
  	else
  		return ERR_PTR(-EINVAL);
  
  	/* Get parent to sys clock */
  	sys_pclk = clk_get(NULL, sys_clk_src[pclk]);
  	if (IS_ERR(sys_pclk))
  		pr_err("Failed to get %s clock
  ", sys_clk_src[pclk]);
  
  	return sys_pclk;
  }
  
  /*
   * In SPEAr1340, we cannot use newfreq directly because we need to actually
   * access a source clock (clk) which might not be ancestor of cpu at present.
   * Hence in SPEAr1340 we would operate on source clock directly before switching
   * cpu clock to it.
   */
  static int spear1340_set_cpu_rate(struct clk *sys_pclk, unsigned long newfreq)
  {
  	struct clk *sys_clk;
  	int ret = 0;
  
  	sys_clk = clk_get_parent(spear_cpufreq.clk);
  	if (IS_ERR(sys_clk)) {
  		pr_err("failed to get cpu's parent (sys) clock
  ");
  		return PTR_ERR(sys_clk);
  	}
  
  	/* Set the rate of the source clock before changing the parent */
  	ret = clk_set_rate(sys_pclk, newfreq);
  	if (ret) {
  		pr_err("Failed to set sys clk rate to %lu
  ", newfreq);
  		return ret;
  	}
  
  	ret = clk_set_parent(sys_clk, sys_pclk);
  	if (ret) {
  		pr_err("Failed to set sys clk parent
  ");
  		return ret;
  	}
  
  	return 0;
  }
  
  static int spear_cpufreq_target(struct cpufreq_policy *policy,

  		unsigned int index)

  {

  	long newfreq;

  	struct clk *srcclk;

  	int ret, mult = 1;

  	newfreq = spear_cpufreq.freq_tbl[index].frequency * 1000;

  	if (of_machine_is_compatible("st,spear1340")) {
  		/*
  		 * SPEAr1340 is special in the sense that due to the possibility
  		 * of multiple clock sources for cpu clk's parent we can have
  		 * different clock source for different frequency of cpu clk.
  		 * Hence we need to choose one from amongst these possible clock
  		 * sources.
  		 */
  		srcclk = spear1340_cpu_get_possible_parent(newfreq);
  		if (IS_ERR(srcclk)) {
  			pr_err("Failed to get src clk
  ");
  			return PTR_ERR(srcclk);
  		}
  
  		/* SPEAr1340: src clk is always 2 * intended cpu clk */
  		mult = 2;
  	} else {
  		/*
  		 * src clock to be altered is ancestor of cpu clock. Hence we
  		 * can directly work on cpu clk
  		 */
  		srcclk = spear_cpufreq.clk;
  	}
  
  	newfreq = clk_round_rate(srcclk, newfreq * mult);

  	if (newfreq <= 0) {

  		pr_err("clk_round_rate failed for cpu src clock
  ");
  		return newfreq;
  	}

  	if (mult == 2)
  		ret = spear1340_set_cpu_rate(srcclk, newfreq);
  	else
  		ret = clk_set_rate(spear_cpufreq.clk, newfreq);

  	if (ret)

  		pr_err("CPU Freq: cpu clk_set_rate failed: %d
  ", ret);

  	return ret;
  }
  
  static int spear_cpufreq_init(struct cpufreq_policy *policy)
  {

  	policy->clk = spear_cpufreq.clk;

  	return cpufreq_generic_init(policy, spear_cpufreq.freq_tbl,
  			spear_cpufreq.transition_latency);

  }

  static struct cpufreq_driver spear_cpufreq_driver = {
  	.name		= "cpufreq-spear",

  	.flags		= CPUFREQ_STICKY | CPUFREQ_NEED_INITIAL_FREQ_CHECK,

  	.verify		= cpufreq_generic_frequency_table_verify,

  	.target_index	= spear_cpufreq_target,

  	.get		= cpufreq_generic_get,

  	.init		= spear_cpufreq_init,

  	.attr		= cpufreq_generic_attr,

  };

  static int spear_cpufreq_probe(struct platform_device *pdev)

  {
  	struct device_node *np;
  	const struct property *prop;
  	struct cpufreq_frequency_table *freq_tbl;
  	const __be32 *val;
  	int cnt, i, ret;

  	np = of_cpu_device_node_get(0);

  	if (!np) {

  		pr_err("No cpu node found
  ");

  		return -ENODEV;
  	}
  
  	if (of_property_read_u32(np, "clock-latency",
  				&spear_cpufreq.transition_latency))
  		spear_cpufreq.transition_latency = CPUFREQ_ETERNAL;
  
  	prop = of_find_property(np, "cpufreq_tbl", NULL);
  	if (!prop || !prop->value) {

  		pr_err("Invalid cpufreq_tbl
  ");

  		ret = -ENODEV;
  		goto out_put_node;
  	}
  
  	cnt = prop->length / sizeof(u32);
  	val = prop->value;

  	freq_tbl = kcalloc(cnt + 1, sizeof(*freq_tbl), GFP_KERNEL);

  	if (!freq_tbl) {
  		ret = -ENOMEM;
  		goto out_put_node;
  	}

  	for (i = 0; i < cnt; i++)

  		freq_tbl[i].frequency = be32_to_cpup(val++);

  	freq_tbl[i].frequency = CPUFREQ_TABLE_END;
  
  	spear_cpufreq.freq_tbl = freq_tbl;
  
  	of_node_put(np);
  
  	spear_cpufreq.clk = clk_get(NULL, "cpu_clk");
  	if (IS_ERR(spear_cpufreq.clk)) {
  		pr_err("Unable to get CPU clock
  ");
  		ret = PTR_ERR(spear_cpufreq.clk);
  		goto out_put_mem;
  	}
  
  	ret = cpufreq_register_driver(&spear_cpufreq_driver);
  	if (!ret)
  		return 0;
  
  	pr_err("failed register driver: %d
  ", ret);
  	clk_put(spear_cpufreq.clk);
  
  out_put_mem:
  	kfree(freq_tbl);
  	return ret;
  
  out_put_node:
  	of_node_put(np);
  	return ret;
  }

  
  static struct platform_driver spear_cpufreq_platdrv = {
  	.driver = {
  		.name	= "spear-cpufreq",

  	},
  	.probe		= spear_cpufreq_probe,
  };
  module_platform_driver(spear_cpufreq_platdrv);

  
  MODULE_AUTHOR("Deepak Sikri <deepak.sikri@st.com>");
  MODULE_DESCRIPTION("SPEAr CPUFreq driver");
  MODULE_LICENSE("GPL");