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69 lines
1.7 KiB
69 lines
1.7 KiB
/* Ported over from i386 by AK, original copyright was:
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*
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* (C) Dominik Brodowski <linux@brodo.de> 2003
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*
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* Driver to use the Power Management Timer (PMTMR) available in some
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* southbridges as primary timing source for the Linux kernel.
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*
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* Based on parts of linux/drivers/acpi/hardware/hwtimer.c, timer_pit.c,
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* timer_hpet.c, and on Arjan van de Ven's implementation for 2.4.
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*
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* This file is licensed under the GPL v2.
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*
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* Dropped all the hardware bug workarounds for now. Hopefully they
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* are not needed on 64bit chipsets.
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*/
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#include <linux/jiffies.h>
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#include <linux/kernel.h>
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#include <linux/time.h>
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#include <linux/init.h>
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#include <linux/cpumask.h>
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#include <asm/io.h>
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#include <asm/proto.h>
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#include <asm/msr.h>
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#include <asm/vsyscall.h>
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#define ACPI_PM_MASK 0xFFFFFF /* limit it to 24 bits */
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static inline u32 cyc2us(u32 cycles)
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{
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/* The Power Management Timer ticks at 3.579545 ticks per microsecond.
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* 1 / PM_TIMER_FREQUENCY == 0.27936511 =~ 286/1024 [error: 0.024%]
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*
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* Even with HZ = 100, delta is at maximum 35796 ticks, so it can
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* easily be multiplied with 286 (=0x11E) without having to fear
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* u32 overflows.
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*/
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cycles *= 286;
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return (cycles >> 10);
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}
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static unsigned pmtimer_wait_tick(void)
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{
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u32 a, b;
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for (a = b = inl(pmtmr_ioport) & ACPI_PM_MASK;
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a == b;
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b = inl(pmtmr_ioport) & ACPI_PM_MASK)
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cpu_relax();
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return b;
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}
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/* note: wait time is rounded up to one tick */
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void pmtimer_wait(unsigned us)
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{
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u32 a, b;
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a = pmtimer_wait_tick();
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do {
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b = inl(pmtmr_ioport);
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cpu_relax();
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} while (cyc2us(b - a) < us);
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}
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static int __init nopmtimer_setup(char *s)
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{
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pmtmr_ioport = 0;
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return 1;
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}
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__setup("nopmtimer", nopmtimer_setup);
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