30f3174d1c
Apparently some systems export valid HPET addresses, but hpet_enable() fails. Then when the HPET clocksource starts up, it only checks for a valid HPET address, and the result is a system where time does not advance. See http://bugme.osdl.org/show_bug.cgi?id=7062 for details. This patch just makes sure we better check that the HPET is functional before registering the HPET clocksource. Signed-off-by: John Stultz <johnstul@us.ibm.com> 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 CLOCKSOURCE_MASK(32)
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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 = 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 (!is_hpet_enabled())
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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 clocksource_register(&clocksource_hpet);
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}
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module_init(init_hpet_clocksource);
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