drivers/clocksource/mmio.c

   1 /*
   2  * Generic MMIO clocksource support
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License version 2 as
   6  * published by the Free Software Foundation.
   7  */
   8 #include <linux/clocksource.h>
   9 #include <linux/errno.h>
  10 #include <linux/init.h>
  11 #include <linux/slab.h>
  12
  13 struct clocksource_mmio {
  14         void __iomem *reg;
  15         struct clocksource clksrc;
  16 };
  17
  18 static inline struct clocksource_mmio *to_mmio_clksrc(struct clocksource *c)
  19 {
  20         return container_of(c, struct clocksource_mmio, clksrc);
  21 }
  22
  23 u64 clocksource_mmio_readl_up(struct clocksource *c)
  24 {
  25         return (u64)readl_relaxed(to_mmio_clksrc(c)->reg);
  26 }
  27
  28 u64 clocksource_mmio_readl_down(struct clocksource *c)
  29 {
  30         return ~(u64)readl_relaxed(to_mmio_clksrc(c)->reg) & c->mask;
  31 }
  32
  33 u64 clocksource_mmio_readw_up(struct clocksource *c)
  34 {
  35         return (u64)readw_relaxed(to_mmio_clksrc(c)->reg);
  36 }
  37
  38 u64 clocksource_mmio_readw_down(struct clocksource *c)
  39 {
  40         return ~(u64)readw_relaxed(to_mmio_clksrc(c)->reg) & c->mask;
  41 }
  42
  43 /**
  44  * clocksource_mmio_init - Initialize a simple mmio based clocksource
  45  * @base:       Virtual address of the clock readout register
  46  * @name:       Name of the clocksource
  47  * @hz:         Frequency of the clocksource in Hz
  48  * @rating:     Rating of the clocksource
  49  * @bits:       Number of valid bits
  50  * @read:       One of clocksource_mmio_read*() above
  51  */
  52 int __init clocksource_mmio_init(void __iomem *base, const char *name,
  53         unsigned long hz, int rating, unsigned bits,
  54         u64 (*read)(struct clocksource *))
  55 {
  56         struct clocksource_mmio *cs;
  57
  58         if (bits > 64 || bits < 16)
  59                 return -EINVAL;
  60
  61         cs = kzalloc(sizeof(struct clocksource_mmio), GFP_KERNEL);
  62         if (!cs)
  63                 return -ENOMEM;
  64
  65         cs->reg = base;
  66         cs->clksrc.name = name;
  67         cs->clksrc.rating = rating;
  68         cs->clksrc.read = read;
  69         cs->clksrc.mask = CLOCKSOURCE_MASK(bits);
  70         cs->clksrc.flags = CLOCK_SOURCE_IS_CONTINUOUS;
  71
  72         return clocksource_register_hz(&cs->clksrc, hz);
  73 }