arch/metag/kernel/clock.c

   1 /*
   2  * arch/metag/kernel/clock.c
   3  *
   4  * Copyright (C) 2012 Imagination Technologies Ltd.
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 as
   8  * published by the Free Software Foundation.
   9  */
  10
  11 #include <linux/clk.h>
  12 #include <linux/delay.h>
  13 #include <linux/io.h>
  14 #include <linux/of.h>
  15
  16 #include <asm/param.h>
  17 #include <asm/clock.h>
  18
  19 struct meta_clock_desc _meta_clock;
  20
  21 /* Default machine get_core_freq callback. */
  22 static unsigned long get_core_freq_default(void)
  23 {
  24 #ifdef CONFIG_METAG_META21
  25         /*
  26          * Meta 2 cores divide down the core clock for the Meta timers, so we
  27          * can estimate the core clock from the divider.
  28          */
  29         return (metag_in32(EXPAND_TIMER_DIV) + 1) * 1000000;
  30 #else
  31         /*
  32          * On Meta 1 we don't know the core clock, but assuming the Meta timer
  33          * is correct it can be estimated based on loops_per_jiffy.
  34          */
  35         return (loops_per_jiffy * HZ * 5) >> 1;
  36 #endif
  37 }
  38
  39 static struct clk *clk_core;
  40
  41 /* Clk based get_core_freq callback. */
  42 static unsigned long get_core_freq_clk(void)
  43 {
  44         return clk_get_rate(clk_core);
  45 }
  46
  47 /**
  48  * init_metag_core_clock() - Set up core clock from devicetree.
  49  *
  50  * Checks to see if a "core" clock is provided in the device tree, and overrides
  51  * the get_core_freq callback to use it.
  52  */
  53 static void __init init_metag_core_clock(void)
  54 {
  55         /*
  56          * See if a core clock is provided by the devicetree (and
  57          * registered by the init callback above).
  58          */
  59         struct device_node *node;
  60         node = of_find_compatible_node(NULL, NULL, "img,meta");
  61         if (!node) {
  62                 pr_warn("%s: no compatible img,meta DT node found\n",
  63                         __func__);
  64                 return;
  65         }
  66
  67         clk_core = of_clk_get_by_name(node, "core");
  68         if (IS_ERR(clk_core)) {
  69                 pr_warn("%s: no core clock found in DT\n",
  70                         __func__);
  71                 return;
  72         }
  73
  74         /*
  75          * Override the core frequency callback to use
  76          * this clk.
  77          */
  78         _meta_clock.get_core_freq = get_core_freq_clk;
  79 }
  80
  81 /**
  82  * init_metag_clocks() - Set up clocks from devicetree.
  83  *
  84  * Set up important clocks from device tree. In particular any needed for clock
  85  * sources.
  86  */
  87 void __init init_metag_clocks(void)
  88 {
  89         init_metag_core_clock();
  90
  91         pr_info("Core clock frequency: %lu Hz\n", get_coreclock());
  92 }
  93
  94 /**
  95  * setup_meta_clocks() - Early set up of the Meta clock.
  96  * @desc:       Clock descriptor usually provided by machine description
  97  *
  98  * Ensures all callbacks are valid.
  99  */
 100 void __init setup_meta_clocks(struct meta_clock_desc *desc)
 101 {
 102         /* copy callbacks */
 103         if (desc)
 104                 _meta_clock = *desc;
 105
 106         /* set fallback functions */
 107         if (!_meta_clock.get_core_freq)
 108                 _meta_clock.get_core_freq = get_core_freq_default;
 109 }
 110