drivers/clocksource/versatile.c

   1 /*
   2  * This program is free software; you can redistribute it and/or modify
   3  * it under the terms of the GNU General Public License version 2 as
   4  * published by the Free Software Foundation.
   5  *
   6  * This program is distributed in the hope that it will be useful,
   7  * but WITHOUT ANY WARRANTY; without even the implied warranty of
   8  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   9  * GNU General Public License for more details.
  10  *
  11  * Copyright (C) 2014 ARM Limited
  12  */
  13
  14 #include <linux/clocksource.h>
  15 #include <linux/io.h>
  16 #include <linux/of_address.h>
  17 #include <linux/sched_clock.h>
  18
  19 #define SYS_24MHZ 0x05c
  20
  21 static void __iomem *versatile_sys_24mhz;
  22
  23 static u64 notrace versatile_sys_24mhz_read(void)
  24 {
  25         return readl(versatile_sys_24mhz);
  26 }
  27
  28 static void __init versatile_sched_clock_init(struct device_node *node)
  29 {
  30         void __iomem *base = of_iomap(node, 0);
  31
  32         if (!base)
  33                 return;
  34
  35         versatile_sys_24mhz = base + SYS_24MHZ;
  36
  37         sched_clock_register(versatile_sys_24mhz_read, 32, 24000000);
  38 }
  39 CLOCKSOURCE_OF_DECLARE(versatile, "arm,vexpress-sysreg",
  40                        versatile_sched_clock_init);