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 static void __init shmobile_setup_delay_hz(unsigned int max_cpu_core_hz,
  22                                            unsigned int mult, unsigned int div)
  23 {
  24         /* calculate a worst-case loops-per-jiffy value
  25          * based on maximum cpu core hz setting and the
  26          * __delay() implementation in arch/arm/lib/delay.S
  27          *
  28          * this will result in a longer delay than expected
  29          * when the cpu core runs on lower frequencies.
  30          */
  31
  32         unsigned int value = HZ * div / mult;
  33
  34         if (!preset_lpj)
  35                 preset_lpj = max_cpu_core_hz / value;
  36 }
  37
  38 void __init shmobile_init_delay(void)
  39 {
  40         struct device_node *np, *cpus;
  41         bool is_a7_a8_a9 = false;
  42         bool is_a15 = false;
  43         bool has_arch_timer = false;
  44         u32 max_freq = 0;
  45
  46         cpus = of_find_node_by_path("/cpus");
  47         if (!cpus)
  48                 return;
  49
  50         for_each_child_of_node(cpus, np) {
  51                 u32 freq;
  52
  53                 if (!of_property_read_u32(np, "clock-frequency", &freq))
  54                         max_freq = max(max_freq, freq);
  55
  56                 if (of_device_is_compatible(np, "arm,cortex-a8") ||
  57                     of_device_is_compatible(np, "arm,cortex-a9")) {
  58                         is_a7_a8_a9 = true;
  59                 } else if (of_device_is_compatible(np, "arm,cortex-a7")) {
  60                         is_a7_a8_a9 = true;
  61                         has_arch_timer = true;
  62                 } else if (of_device_is_compatible(np, "arm,cortex-a15")) {
  63                         is_a15 = true;
  64                         has_arch_timer = true;
  65                 }
  66         }
  67
  68         of_node_put(cpus);
  69
  70         if (!max_freq)
  71                 return;
  72
  73         if (!has_arch_timer || !IS_ENABLED(CONFIG_ARM_ARCH_TIMER)) {
  74                 if (is_a7_a8_a9)
  75                         shmobile_setup_delay_hz(max_freq, 1, 3);
  76                 else if (is_a15)
  77                         shmobile_setup_delay_hz(max_freq, 2, 4);
  78         }
  79 }