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

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (C) 2016 Rafał Miłecki <rafal@milecki.pl>
   4  */
   5
   6 #include <linux/clk-provider.h>
   7 #include <linux/err.h>
   8 #include <linux/io.h>
   9 #include <linux/mfd/syscon.h>
  10 #include <linux/of.h>
  11 #include <linux/of_address.h>
  12 #include <linux/regmap.h>
  13 #include <linux/slab.h>
  14
  15 #define PMU_XTAL_FREQ_RATIO                     0x66c
  16 #define  XTAL_ALP_PER_4ILP                      0x00001fff
  17 #define  XTAL_CTL_EN                            0x80000000
  18 #define PMU_SLOW_CLK_PERIOD                     0x6dc
  19
  20 struct bcm53573_ilp {
  21         struct clk_hw hw;
  22         struct regmap *regmap;
  23 };
  24
  25 static int bcm53573_ilp_enable(struct clk_hw *hw)
  26 {
  27         struct bcm53573_ilp *ilp = container_of(hw, struct bcm53573_ilp, hw);
  28
  29         regmap_write(ilp->regmap, PMU_SLOW_CLK_PERIOD, 0x10199);
  30         regmap_write(ilp->regmap, 0x674, 0x10000);
  31
  32         return 0;
  33 }
  34
  35 static void bcm53573_ilp_disable(struct clk_hw *hw)
  36 {
  37         struct bcm53573_ilp *ilp = container_of(hw, struct bcm53573_ilp, hw);
  38
  39         regmap_write(ilp->regmap, PMU_SLOW_CLK_PERIOD, 0);
  40         regmap_write(ilp->regmap, 0x674, 0);
  41 }
  42
  43 static unsigned long bcm53573_ilp_recalc_rate(struct clk_hw *hw,
  44                                               unsigned long parent_rate)
  45 {
  46         struct bcm53573_ilp *ilp = container_of(hw, struct bcm53573_ilp, hw);
  47         struct regmap *regmap = ilp->regmap;
  48         u32 last_val, cur_val;
  49         int sum = 0, num = 0, loop_num = 0;
  50         int avg;
  51
  52         /* Enable measurement */
  53         regmap_write(regmap, PMU_XTAL_FREQ_RATIO, XTAL_CTL_EN);
  54
  55         /* Read initial value */
  56         regmap_read(regmap, PMU_XTAL_FREQ_RATIO, &last_val);
  57         last_val &= XTAL_ALP_PER_4ILP;
  58
  59         /*
  60          * At minimum we should loop for a bit to let hardware do the
  61          * measurement. This isn't very accurate however, so for a better
  62          * precision lets try getting 20 different values for and use average.
  63          */
  64         while (num < 20) {
  65                 regmap_read(regmap, PMU_XTAL_FREQ_RATIO, &cur_val);
  66                 cur_val &= XTAL_ALP_PER_4ILP;
  67
  68                 if (cur_val != last_val) {
  69                         /* Got different value, use it */
  70                         sum += cur_val;
  71                         num++;
  72                         loop_num = 0;
  73                         last_val = cur_val;
  74                 } else if (++loop_num > 5000) {
  75                         /* Same value over and over, give up */
  76                         sum += cur_val;
  77                         num++;
  78                         break;
  79                 }
  80
  81                 cpu_relax();
  82         }
  83
  84         /* Disable measurement to save power */
  85         regmap_write(regmap, PMU_XTAL_FREQ_RATIO, 0x0);
  86
  87         avg = sum / num;
  88
  89         return parent_rate * 4 / avg;
  90 }
  91
  92 static const struct clk_ops bcm53573_ilp_clk_ops = {
  93         .enable = bcm53573_ilp_enable,
  94         .disable = bcm53573_ilp_disable,
  95         .recalc_rate = bcm53573_ilp_recalc_rate,
  96 };
  97
  98 static void bcm53573_ilp_init(struct device_node *np)
  99 {
 100         struct bcm53573_ilp *ilp;
 101         struct clk_init_data init = { };
 102         const char *parent_name;
 103         int err;
 104
 105         ilp = kzalloc(sizeof(*ilp), GFP_KERNEL);
 106         if (!ilp)
 107                 return;
 108
 109         parent_name = of_clk_get_parent_name(np, 0);
 110         if (!parent_name) {
 111                 err = -ENOENT;
 112                 goto err_free_ilp;
 113         }
 114
 115         ilp->regmap = syscon_node_to_regmap(of_get_parent(np));
 116         if (IS_ERR(ilp->regmap)) {
 117                 err = PTR_ERR(ilp->regmap);
 118                 goto err_free_ilp;
 119         }
 120
 121         init.name = np->name;
 122         init.ops = &bcm53573_ilp_clk_ops;
 123         init.parent_names = &parent_name;
 124         init.num_parents = 1;
 125
 126         ilp->hw.init = &init;
 127         err = clk_hw_register(NULL, &ilp->hw);
 128         if (err)
 129                 goto err_free_ilp;
 130
 131         err = of_clk_add_hw_provider(np, of_clk_hw_simple_get, &ilp->hw);
 132         if (err)
 133                 goto err_clk_hw_unregister;
 134
 135         return;
 136
 137 err_clk_hw_unregister:
 138         clk_hw_unregister(&ilp->hw);
 139 err_free_ilp:
 140         kfree(ilp);
 141         pr_err("Failed to init ILP clock: %d\n", err);
 142 }
 143
 144 /* We need it very early for arch code, before device model gets ready */
 145 CLK_OF_DECLARE(bcm53573_ilp_clk, "brcm,bcm53573-ilp", bcm53573_ilp_init);