LXR linux/drivers/clk/bcm/clk-bcm53573-ilp.c

   1/*
   2 * Copyright (C) 2016 Rafał Miłecki <rafal@milecki.pl>
   3 *
   4 * This program is free software; you can redistribute it and/or modify
   5 * it under the terms of the GNU General Public License version 2 as
   6 * published by the Free Software Foundation.
   7 */
   8
   9#include <linux/clk-provider.h>
  10#include <linux/err.h>
  11#include <linux/io.h>
  12#include <linux/mfd/syscon.h>
  13#include <linux/of.h>
  14#include <linux/of_address.h>
  15#include <linux/regmap.h>
  16#include <linux/slab.h>
  17
  18#define PMU_XTAL_FREQ_RATIO                     0x66c
  19#define  XTAL_ALP_PER_4ILP                      0x00001fff
  20#define  XTAL_CTL_EN                            0x80000000
  21#define PMU_SLOW_CLK_PERIOD                     0x6dc
  22
  23struct bcm53573_ilp {
  24        struct clk_hw hw;
  25        struct regmap *regmap;
  26};
  27
  28static int bcm53573_ilp_enable(struct clk_hw *hw)
  29{
  30        struct bcm53573_ilp *ilp = container_of(hw, struct bcm53573_ilp, hw);
  31
  32        regmap_write(ilp->regmap, PMU_SLOW_CLK_PERIOD, 0x10199);
  33        regmap_write(ilp->regmap, 0x674, 0x10000);
  34
  35        return 0;
  36}
  37
  38static void bcm53573_ilp_disable(struct clk_hw *hw)
  39{
  40        struct bcm53573_ilp *ilp = container_of(hw, struct bcm53573_ilp, hw);
  41
  42        regmap_write(ilp->regmap, PMU_SLOW_CLK_PERIOD, 0);
  43        regmap_write(ilp->regmap, 0x674, 0);
  44}
  45
  46static unsigned long bcm53573_ilp_recalc_rate(struct clk_hw *hw,
  47                                              unsigned long parent_rate)
  48{
  49        struct bcm53573_ilp *ilp = container_of(hw, struct bcm53573_ilp, hw);
  50        struct regmap *regmap = ilp->regmap;
  51        u32 last_val, cur_val;
  52        int sum = 0, num = 0, loop_num = 0;
  53        int avg;
  54
  55        /* Enable measurement */
  56        regmap_write(regmap, PMU_XTAL_FREQ_RATIO, XTAL_CTL_EN);
  57
  58        /* Read initial value */
  59        regmap_read(regmap, PMU_XTAL_FREQ_RATIO, &last_val);
  60        last_val &= XTAL_ALP_PER_4ILP;
  61
  62        /*
  63         * At minimum we should loop for a bit to let hardware do the
  64         * measurement. This isn't very accurate however, so for a better
  65         * precision lets try getting 20 different values for and use average.
  66         */
  67        while (num < 20) {
  68                regmap_read(regmap, PMU_XTAL_FREQ_RATIO, &cur_val);
  69                cur_val &= XTAL_ALP_PER_4ILP;
  70
  71                if (cur_val != last_val) {
  72                        /* Got different value, use it */
  73                        sum += cur_val;
  74                        num++;
  75                        loop_num = 0;
  76                        last_val = cur_val;
  77                } else if (++loop_num > 5000) {
  78                        /* Same value over and over, give up */
  79                        sum += cur_val;
  80                        num++;
  81                        break;
  82                }
  83
  84                cpu_relax();
  85        }
  86
  87        /* Disable measurement to save power */
  88        regmap_write(regmap, PMU_XTAL_FREQ_RATIO, 0x0);
  89
  90        avg = sum / num;
  91
  92        return parent_rate * 4 / avg;
  93}
  94
  95static const struct clk_ops bcm53573_ilp_clk_ops = {
  96        .enable = bcm53573_ilp_enable,
  97        .disable = bcm53573_ilp_disable,
  98        .recalc_rate = bcm53573_ilp_recalc_rate,
  99};
 100
 101static void bcm53573_ilp_init(struct device_node *np)
 102{
 103        struct bcm53573_ilp *ilp;
 104        struct clk_init_data init = { };
 105        const char *parent_name;
 106        int err;
 107
 108        ilp = kzalloc(sizeof(*ilp), GFP_KERNEL);
 109        if (!ilp)
 110                return;
 111
 112        parent_name = of_clk_get_parent_name(np, 0);
 113        if (!parent_name) {
 114                err = -ENOENT;
 115                goto err_free_ilp;
 116        }
 117
 118        ilp->regmap = syscon_node_to_regmap(of_get_parent(np));
 119        if (IS_ERR(ilp->regmap)) {
 120                err = PTR_ERR(ilp->regmap);
 121                goto err_free_ilp;
 122        }
 123
 124        init.name = np->name;
 125        init.ops = &bcm53573_ilp_clk_ops;
 126        init.parent_names = &parent_name;
 127        init.num_parents = 1;
 128
 129        ilp->hw.init = &init;
 130        err = clk_hw_register(NULL, &ilp->hw);
 131        if (err)
 132                goto err_free_ilp;
 133
 134        err = of_clk_add_hw_provider(np, of_clk_hw_simple_get, &ilp->hw);
 135        if (err)
 136                goto err_clk_hw_unregister;
 137
 138        return;
 139
 140err_clk_hw_unregister:
 141        clk_hw_unregister(&ilp->hw);
 142err_free_ilp:
 143        kfree(ilp);
 144        pr_err("Failed to init ILP clock: %d\n", err);
 145}
 146
 147/* We need it very early for arch code, before device model gets ready */
 148CLK_OF_DECLARE(bcm53573_ilp_clk, "brcm,bcm53573-ilp", bcm53573_ilp_init);
 149