/*
   * Copyright (c) 2014 Samsung Electronics Co., Ltd.
   * Author: Thomas Abraham <thomas.ab@samsung.com>
   *
   * Copyright (c) 2015 Samsung Electronics Co., Ltd.
   * Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.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 file contains the utility function to register CPU clock for Samsung
   * Exynos platforms. A CPU clock is defined as a clock supplied to a CPU or a
   * group of CPUs. The CPU clock is typically derived from a hierarchy of clock
   * blocks which includes mux and divider blocks. There are a number of other
   * auxiliary clocks supplied to the CPU domain such as the debug blocks and AXI
   * clock for CPU domain. The rates of these auxiliary clocks are related to the
   * CPU clock rate and this relation is usually specified in the hardware manual
   * of the SoC or supplied after the SoC characterization.
   *
   * The below implementation of the CPU clock allows the rate changes of the CPU
   * clock and the corresponding rate changes of the auxillary clocks of the CPU
   * domain. The platform clock driver provides a clock register configuration
   * for each configurable rate which is then used to program the clock hardware
   * registers to acheive a fast co-oridinated rate change for all the CPU domain
   * clocks.
   *
   * On a rate change request for the CPU clock, the rate change is propagated
   * upto the PLL supplying the clock to the CPU domain clock blocks. While the
   * CPU domain PLL is reconfigured, the CPU domain clocks are driven using an
   * alternate clock source. If required, the alternate clock source is divided
   * down in order to keep the output clock rate within the previous OPP limits.
  */
  
  #include <linux/errno.h>
  #include <linux/slab.h>
  #include <linux/clk.h>
  #include <linux/clk-provider.h>
  #include "clk-cpu.h"
  
  #define E4210_SRC_CPU		0x0
  #define E4210_STAT_CPU		0x200
  #define E4210_DIV_CPU0		0x300
  #define E4210_DIV_CPU1		0x304
  #define E4210_DIV_STAT_CPU0	0x400
  #define E4210_DIV_STAT_CPU1	0x404
  
  #define E4210_DIV0_RATIO0_MASK	0x7
  #define E4210_DIV1_HPM_MASK	(0x7 << 4)
  #define E4210_DIV1_COPY_MASK	(0x7 << 0)
  #define E4210_MUX_HPM_MASK	(1 << 20)
  #define E4210_DIV0_ATB_SHIFT	16
  #define E4210_DIV0_ATB_MASK	(DIV_MASK << E4210_DIV0_ATB_SHIFT)
  
  #define MAX_DIV			8
  #define DIV_MASK		7
  #define DIV_MASK_ALL		0xffffffff
  #define MUX_MASK		7
  
  /*
   * Helper function to wait until divider(s) have stabilized after the divider
   * value has changed.
   */
  static void wait_until_divider_stable(void __iomem *div_reg, unsigned long mask)
  {
  	unsigned long timeout = jiffies + msecs_to_jiffies(10);
  
  	do {
  		if (!(readl(div_reg) & mask))
  			return;
  	} while (time_before(jiffies, timeout));
  
  	if (!(readl(div_reg) & mask))
  		return;
  
  	pr_err("%s: timeout in divider stablization
  ", __func__);
  }
  
  /*
   * Helper function to wait until mux has stabilized after the mux selection
   * value was changed.
   */
  static void wait_until_mux_stable(void __iomem *mux_reg, u32 mux_pos,
  					unsigned long mux_value)
  {
  	unsigned long timeout = jiffies + msecs_to_jiffies(10);
  
  	do {
  		if (((readl(mux_reg) >> mux_pos) & MUX_MASK) == mux_value)
  			return;
  	} while (time_before(jiffies, timeout));
  
  	if (((readl(mux_reg) >> mux_pos) & MUX_MASK) == mux_value)
  		return;
  
  	pr_err("%s: re-parenting mux timed-out
  ", __func__);
  }
  
  /* common round rate callback useable for all types of CPU clocks */
  static long exynos_cpuclk_round_rate(struct clk_hw *hw,
  			unsigned long drate, unsigned long *prate)
  {
  	struct clk_hw *parent = clk_hw_get_parent(hw);
  	*prate = clk_hw_round_rate(parent, drate);
  	return *prate;
  }
  
  /* common recalc rate callback useable for all types of CPU clocks */
  static unsigned long exynos_cpuclk_recalc_rate(struct clk_hw *hw,
  			unsigned long parent_rate)
  {
  	/*
  	 * The CPU clock output (armclk) rate is the same as its parent
  	 * rate. Although there exist certain dividers inside the CPU
  	 * clock block that could be used to divide the parent clock,
  	 * the driver does not make use of them currently, except during
  	 * frequency transitions.
  	 */
  	return parent_rate;
  }
  
  static const struct clk_ops exynos_cpuclk_clk_ops = {
  	.recalc_rate = exynos_cpuclk_recalc_rate,
  	.round_rate = exynos_cpuclk_round_rate,
  };
  
  /*
   * Helper function to set the 'safe' dividers for the CPU clock. The parameters
   * div and mask contain the divider value and the register bit mask of the
   * dividers to be programmed.
   */
  static void exynos_set_safe_div(void __iomem *base, unsigned long div,
  					unsigned long mask)
  {
  	unsigned long div0;
  
  	div0 = readl(base + E4210_DIV_CPU0);
  	div0 = (div0 & ~mask) | (div & mask);
  	writel(div0, base + E4210_DIV_CPU0);
  	wait_until_divider_stable(base + E4210_DIV_STAT_CPU0, mask);
  }
  
  /* handler for pre-rate change notification from parent clock */
  static int exynos_cpuclk_pre_rate_change(struct clk_notifier_data *ndata,
  			struct exynos_cpuclk *cpuclk, void __iomem *base)
  {
  	const struct exynos_cpuclk_cfg_data *cfg_data = cpuclk->cfg;
  	unsigned long alt_prate = clk_get_rate(cpuclk->alt_parent);
  	unsigned long alt_div = 0, alt_div_mask = DIV_MASK;
  	unsigned long div0, div1 = 0, mux_reg;
  	unsigned long flags;
  
  	/* find out the divider values to use for clock data */
  	while ((cfg_data->prate * 1000) != ndata->new_rate) {
  		if (cfg_data->prate == 0)
  			return -EINVAL;
  		cfg_data++;
  	}
  
  	spin_lock_irqsave(cpuclk->lock, flags);
  
  	/*
  	 * For the selected PLL clock frequency, get the pre-defined divider
  	 * values. If the clock for sclk_hpm is not sourced from apll, then
  	 * the values for DIV_COPY and DIV_HPM dividers need not be set.
  	 */
  	div0 = cfg_data->div0;
  	if (cpuclk->flags & CLK_CPU_HAS_DIV1) {
  		div1 = cfg_data->div1;
  		if (readl(base + E4210_SRC_CPU) & E4210_MUX_HPM_MASK)
  			div1 = readl(base + E4210_DIV_CPU1) &
  				(E4210_DIV1_HPM_MASK | E4210_DIV1_COPY_MASK);
  	}
  
  	/*
  	 * If the old parent clock speed is less than the clock speed of
  	 * the alternate parent, then it should be ensured that at no point
  	 * the armclk speed is more than the old_prate until the dividers are
  	 * set.  Also workaround the issue of the dividers being set to lower
  	 * values before the parent clock speed is set to new lower speed
  	 * (this can result in too high speed of armclk output clocks).
  	 */
  	if (alt_prate > ndata->old_rate || ndata->old_rate > ndata->new_rate) {
  		unsigned long tmp_rate = min(ndata->old_rate, ndata->new_rate);
  
  		alt_div = DIV_ROUND_UP(alt_prate, tmp_rate) - 1;
  		WARN_ON(alt_div >= MAX_DIV);
  
  		if (cpuclk->flags & CLK_CPU_NEEDS_DEBUG_ALT_DIV) {
  			/*
  			 * In Exynos4210, ATB clock parent is also mout_core. So
  			 * ATB clock also needs to be mantained at safe speed.
  			 */
  			alt_div |= E4210_DIV0_ATB_MASK;
  			alt_div_mask |= E4210_DIV0_ATB_MASK;
  		}
  		exynos_set_safe_div(base, alt_div, alt_div_mask);
  		div0 |= alt_div;
  	}
  
  	/* select sclk_mpll as the alternate parent */
  	mux_reg = readl(base + E4210_SRC_CPU);
  	writel(mux_reg | (1 << 16), base + E4210_SRC_CPU);
  	wait_until_mux_stable(base + E4210_STAT_CPU, 16, 2);
  
  	/* alternate parent is active now. set the dividers */
  	writel(div0, base + E4210_DIV_CPU0);
  	wait_until_divider_stable(base + E4210_DIV_STAT_CPU0, DIV_MASK_ALL);
  
  	if (cpuclk->flags & CLK_CPU_HAS_DIV1) {
  		writel(div1, base + E4210_DIV_CPU1);
  		wait_until_divider_stable(base + E4210_DIV_STAT_CPU1,
  				DIV_MASK_ALL);
  	}
  
  	spin_unlock_irqrestore(cpuclk->lock, flags);
  	return 0;
  }
  
  /* handler for post-rate change notification from parent clock */
  static int exynos_cpuclk_post_rate_change(struct clk_notifier_data *ndata,
  			struct exynos_cpuclk *cpuclk, void __iomem *base)
  {
  	const struct exynos_cpuclk_cfg_data *cfg_data = cpuclk->cfg;
  	unsigned long div = 0, div_mask = DIV_MASK;
  	unsigned long mux_reg;
  	unsigned long flags;
  
  	/* find out the divider values to use for clock data */
  	if (cpuclk->flags & CLK_CPU_NEEDS_DEBUG_ALT_DIV) {
  		while ((cfg_data->prate * 1000) != ndata->new_rate) {
  			if (cfg_data->prate == 0)
  				return -EINVAL;
  			cfg_data++;
  		}
  	}
  
  	spin_lock_irqsave(cpuclk->lock, flags);
  
  	/* select mout_apll as the alternate parent */
  	mux_reg = readl(base + E4210_SRC_CPU);
  	writel(mux_reg & ~(1 << 16), base + E4210_SRC_CPU);
  	wait_until_mux_stable(base + E4210_STAT_CPU, 16, 1);
  
  	if (cpuclk->flags & CLK_CPU_NEEDS_DEBUG_ALT_DIV) {
  		div |= (cfg_data->div0 & E4210_DIV0_ATB_MASK);
  		div_mask |= E4210_DIV0_ATB_MASK;
  	}
  
  	exynos_set_safe_div(base, div, div_mask);
  	spin_unlock_irqrestore(cpuclk->lock, flags);
  	return 0;
  }
  
  /*
   * This notifier function is called for the pre-rate and post-rate change
   * notifications of the parent clock of cpuclk.
   */
  static int exynos_cpuclk_notifier_cb(struct notifier_block *nb,
  				unsigned long event, void *data)
  {
  	struct clk_notifier_data *ndata = data;
  	struct exynos_cpuclk *cpuclk;
  	void __iomem *base;
  	int err = 0;
  
  	cpuclk = container_of(nb, struct exynos_cpuclk, clk_nb);
  	base = cpuclk->ctrl_base;
  
  	if (event == PRE_RATE_CHANGE)
  		err = exynos_cpuclk_pre_rate_change(ndata, cpuclk, base);
  	else if (event == POST_RATE_CHANGE)
  		err = exynos_cpuclk_post_rate_change(ndata, cpuclk, base);
  
  	return notifier_from_errno(err);
  }
  
  /* helper function to register a CPU clock */
  int __init exynos_register_cpu_clock(struct samsung_clk_provider *ctx,
  		unsigned int lookup_id, const char *name, const char *parent,
  		const char *alt_parent, unsigned long offset,
  		const struct exynos_cpuclk_cfg_data *cfg,
  		unsigned long num_cfgs, unsigned long flags)
  {
  	struct exynos_cpuclk *cpuclk;
  	struct clk_init_data init;
  	struct clk *clk;
  	int ret = 0;
  
  	cpuclk = kzalloc(sizeof(*cpuclk), GFP_KERNEL);
  	if (!cpuclk)
  		return -ENOMEM;
  
  	init.name = name;
  	init.flags = CLK_SET_RATE_PARENT;
  	init.parent_names = &parent;
  	init.num_parents = 1;
  	init.ops = &exynos_cpuclk_clk_ops;
  
  	cpuclk->hw.init = &init;
  	cpuclk->ctrl_base = ctx->reg_base + offset;
  	cpuclk->lock = &ctx->lock;
  	cpuclk->flags = flags;
  	cpuclk->clk_nb.notifier_call = exynos_cpuclk_notifier_cb;
  
  	cpuclk->alt_parent = __clk_lookup(alt_parent);
  	if (!cpuclk->alt_parent) {
  		pr_err("%s: could not lookup alternate parent %s
  ",
  				__func__, alt_parent);
  		ret = -EINVAL;
  		goto free_cpuclk;
  	}
  
  	clk = __clk_lookup(parent);
  	if (!clk) {
  		pr_err("%s: could not lookup parent clock %s
  ",
  				__func__, parent);
  		ret = -EINVAL;
  		goto free_cpuclk;
  	}
  
  	ret = clk_notifier_register(clk, &cpuclk->clk_nb);
  	if (ret) {
  		pr_err("%s: failed to register clock notifier for %s
  ",
  				__func__, name);
  		goto free_cpuclk;
  	}
  
  	cpuclk->cfg = kmemdup(cfg, sizeof(*cfg) * num_cfgs, GFP_KERNEL);
  	if (!cpuclk->cfg) {
  		pr_err("%s: could not allocate memory for cpuclk data
  ",
  				__func__);
  		ret = -ENOMEM;
  		goto unregister_clk_nb;
  	}
  
  	clk = clk_register(NULL, &cpuclk->hw);
  	if (IS_ERR(clk)) {
  		pr_err("%s: could not register cpuclk %s
  ", __func__,	name);
  		ret = PTR_ERR(clk);
  		goto free_cpuclk_data;
  	}
  
  	samsung_clk_add_lookup(ctx, clk, lookup_id);
  	return 0;
  
  free_cpuclk_data:
  	kfree(cpuclk->cfg);
  unregister_clk_nb:
  	clk_notifier_unregister(__clk_lookup(parent), &cpuclk->clk_nb);
  free_cpuclk:
  	kfree(cpuclk);
  	return ret;
  }