arch/arm/mach-shmobile/timer.c

   1 /*
   2  * SH-Mobile Timer
   3  *
   4  * Copyright (C) 2010  Magnus Damm
   5  * Copyright (C) 2002 - 2009  Paul Mundt
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation; version 2 of the License.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  */
  16 #include <linux/platform_device.h>
  17 #include <linux/clocksource.h>
  18 #include <linux/delay.h>
  19 #include <linux/of_address.h>
  20
  21 #include "common.h"
  22
  23 void __init shmobile_init_delay(void)
  24 {
  25         struct device_node *np, *cpus;
  26         u32 max_freq = 0;
  27
  28         cpus = of_find_node_by_path("/cpus");
  29         if (!cpus)
  30                 return;
  31
  32         for_each_child_of_node(cpus, np) {
  33                 u32 freq;
  34
  35                 if (IS_ENABLED(CONFIG_ARM_ARCH_TIMER) &&
  36                     (of_device_is_compatible(np, "arm,cortex-a7") ||
  37                      of_device_is_compatible(np, "arm,cortex-a15"))) {
  38                         of_node_put(np);
  39                         of_node_put(cpus);
  40                         return;
  41                 }
  42
  43                 if (!of_property_read_u32(np, "clock-frequency", &freq))
  44                         max_freq = max(max_freq, freq);
  45         }
  46
  47         of_node_put(cpus);
  48
  49         if (!max_freq)
  50                 return;
  51
  52         /*
  53          * Calculate a worst-case loops-per-jiffy value
  54          * based on maximum cpu core hz setting and the
  55          * __delay() implementation in arch/arm/lib/delay.S.
  56          *
  57          * This will result in a longer delay than expected
  58          * when the cpu core runs on lower frequencies.
  59          */
  60
  61         if (!preset_lpj)
  62                 preset_lpj = max_freq / HZ;
  63 }