5d0cf410e9
Implement the time sources for i386 (acpi_pm, cyclone, hpet, pit, and tsc). With this patch, the conversion of the i386 arch to the generic timekeeping code should be complete. The patch should be fairly straight forward, only adding the new clocksources. [hirofumi@mail.parknet.co.jp: acpi_pm cleanup] Signed-off-by: John Stultz <johnstul@us.ibm.com> Signed-off-by: Adrian Bunk <bunk@stusta.de> Signed-off-by: Paul Mundt <lethal@linux-sh.org> Signed-off-by: John Stultz <johnstul@us.ibm.com> Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
68 lines
1.5 KiB
C
68 lines
1.5 KiB
C
#include <linux/clocksource.h>
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#include <linux/errno.h>
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#include <linux/hpet.h>
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#include <linux/init.h>
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#include <asm/hpet.h>
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#include <asm/io.h>
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#define HPET_MASK 0xFFFFFFFF
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#define HPET_SHIFT 22
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/* FSEC = 10^-15 NSEC = 10^-9 */
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#define FSEC_PER_NSEC 1000000
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static void *hpet_ptr;
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static cycle_t read_hpet(void)
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{
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return (cycle_t)readl(hpet_ptr);
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}
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static struct clocksource clocksource_hpet = {
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.name = "hpet",
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.rating = 250,
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.read = read_hpet,
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.mask = (cycle_t)HPET_MASK,
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.mult = 0, /* set below */
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.shift = HPET_SHIFT,
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.is_continuous = 1,
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};
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static int __init init_hpet_clocksource(void)
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{
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unsigned long hpet_period;
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void __iomem* hpet_base;
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u64 tmp;
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if (!hpet_address)
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return -ENODEV;
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/* calculate the hpet address: */
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hpet_base =
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(void __iomem*)ioremap_nocache(hpet_address, HPET_MMAP_SIZE);
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hpet_ptr = hpet_base + HPET_COUNTER;
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/* calculate the frequency: */
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hpet_period = readl(hpet_base + HPET_PERIOD);
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/*
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* hpet period is in femto seconds per cycle
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* so we need to convert this to ns/cyc units
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* aproximated by mult/2^shift
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*
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* fsec/cyc * 1nsec/1000000fsec = nsec/cyc = mult/2^shift
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* fsec/cyc * 1ns/1000000fsec * 2^shift = mult
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* fsec/cyc * 2^shift * 1nsec/1000000fsec = mult
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* (fsec/cyc << shift)/1000000 = mult
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* (hpet_period << shift)/FSEC_PER_NSEC = mult
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*/
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tmp = (u64)hpet_period << HPET_SHIFT;
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do_div(tmp, FSEC_PER_NSEC);
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clocksource_hpet.mult = (u32)tmp;
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return register_clocksource(&clocksource_hpet);
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}
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module_init(init_hpet_clocksource);
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