drivers/clocksource/mmio.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Generic MMIO clocksource support
   4  */
   5 #include <linux/clocksource.h>
   6 #include <linux/errno.h>
   7 #include <linux/init.h>
   8 #include <linux/slab.h>
   9
  10 struct clocksource_mmio {
  11         void __iomem *reg;
  12         struct clocksource clksrc;
  13 };
  14
  15 static inline struct clocksource_mmio *to_mmio_clksrc(struct clocksource *c)
  16 {
  17         return container_of(c, struct clocksource_mmio, clksrc);
  18 }
  19
  20 u64 clocksource_mmio_readl_up(struct clocksource *c)
  21 {
  22         return (u64)readl_relaxed(to_mmio_clksrc(c)->reg);
  23 }
  24
  25 u64 clocksource_mmio_readl_down(struct clocksource *c)
  26 {
  27         return ~(u64)readl_relaxed(to_mmio_clksrc(c)->reg) & c->mask;
  28 }
  29
  30 u64 clocksource_mmio_readw_up(struct clocksource *c)
  31 {
  32         return (u64)readw_relaxed(to_mmio_clksrc(c)->reg);
  33 }
  34
  35 u64 clocksource_mmio_readw_down(struct clocksource *c)
  36 {
  37         return ~(u64)readw_relaxed(to_mmio_clksrc(c)->reg) & c->mask;
  38 }
  39
  40 /**
  41  * clocksource_mmio_init - Initialize a simple mmio based clocksource
  42  * @base:       Virtual address of the clock readout register
  43  * @name:       Name of the clocksource
  44  * @hz:         Frequency of the clocksource in Hz
  45  * @rating:     Rating of the clocksource
  46  * @bits:       Number of valid bits
  47  * @read:       One of clocksource_mmio_read*() above
  48  */
  49 int __init clocksource_mmio_init(void __iomem *base, const char *name,
  50         unsigned long hz, int rating, unsigned bits,
  51         u64 (*read)(struct clocksource *))
  52 {
  53         struct clocksource_mmio *cs;
  54
  55         if (bits > 64 || bits < 16)
  56                 return -EINVAL;
  57
  58         cs = kzalloc(sizeof(struct clocksource_mmio), GFP_KERNEL);
  59         if (!cs)
  60                 return -ENOMEM;
  61
  62         cs->reg = base;
  63         cs->clksrc.name = name;
  64         cs->clksrc.rating = rating;
  65         cs->clksrc.read = read;
  66         cs->clksrc.mask = CLOCKSOURCE_MASK(bits);
  67         cs->clksrc.flags = CLOCK_SOURCE_IS_CONTINUOUS;
  68
  69         return clocksource_register_hz(&cs->clksrc, hz);
  70 }