diff options
Diffstat (limited to 'arch/x86/kernel/pmtimer_64.c')
| -rw-r--r-- | arch/x86/kernel/pmtimer_64.c | 69 |
1 files changed, 69 insertions, 0 deletions
diff --git a/arch/x86/kernel/pmtimer_64.c b/arch/x86/kernel/pmtimer_64.c new file mode 100644 index 00000000000..ae8f91214f1 --- /dev/null +++ b/arch/x86/kernel/pmtimer_64.c @@ -0,0 +1,69 @@ +/* Ported over from i386 by AK, original copyright was: + * + * (C) Dominik Brodowski <linux@brodo.de> 2003 + * + * Driver to use the Power Management Timer (PMTMR) available in some + * southbridges as primary timing source for the Linux kernel. + * + * Based on parts of linux/drivers/acpi/hardware/hwtimer.c, timer_pit.c, + * timer_hpet.c, and on Arjan van de Ven's implementation for 2.4. + * + * This file is licensed under the GPL v2. + * + * Dropped all the hardware bug workarounds for now. Hopefully they + * are not needed on 64bit chipsets. + */ + +#include <linux/jiffies.h> +#include <linux/kernel.h> +#include <linux/time.h> +#include <linux/init.h> +#include <linux/cpumask.h> +#include <asm/io.h> +#include <asm/proto.h> +#include <asm/msr.h> +#include <asm/vsyscall.h> + +#define ACPI_PM_MASK 0xFFFFFF /* limit it to 24 bits */ + +static inline u32 cyc2us(u32 cycles) +{ + /* The Power Management Timer ticks at 3.579545 ticks per microsecond. + * 1 / PM_TIMER_FREQUENCY == 0.27936511 =~ 286/1024 [error: 0.024%] + * + * Even with HZ = 100, delta is at maximum 35796 ticks, so it can + * easily be multiplied with 286 (=0x11E) without having to fear + * u32 overflows. + */ + cycles *= 286; + return (cycles >> 10); +} + +static unsigned pmtimer_wait_tick(void) +{ + u32 a, b; + for (a = b = inl(pmtmr_ioport) & ACPI_PM_MASK; + a == b; + b = inl(pmtmr_ioport) & ACPI_PM_MASK) + cpu_relax(); + return b; +} + +/* note: wait time is rounded up to one tick */ +void pmtimer_wait(unsigned us) +{ + u32 a, b; + a = pmtimer_wait_tick(); + do { + b = inl(pmtmr_ioport); + cpu_relax(); + } while (cyc2us(b - a) < us); +} + +static int __init nopmtimer_setup(char *s) +{ + pmtmr_ioport = 0; + return 1; +} + +__setup("nopmtimer", nopmtimer_setup); |