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author | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-04-16 15:20:36 -0700 |
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committer | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-04-16 15:20:36 -0700 |
commit | 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch) | |
tree | 0bba044c4ce775e45a88a51686b5d9f90697ea9d /arch/arm/mach-footbridge/isa-timer.c | |
download | linux-1da177e4c3f41524e886b7f1b8a0c1fc7321cac2.tar.bz2 |
Linux-2.6.12-rc2v2.6.12-rc2
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
Diffstat (limited to 'arch/arm/mach-footbridge/isa-timer.c')
-rw-r--r-- | arch/arm/mach-footbridge/isa-timer.c | 94 |
1 files changed, 94 insertions, 0 deletions
diff --git a/arch/arm/mach-footbridge/isa-timer.c b/arch/arm/mach-footbridge/isa-timer.c new file mode 100644 index 000000000000..a4fefa0bb5a1 --- /dev/null +++ b/arch/arm/mach-footbridge/isa-timer.c @@ -0,0 +1,94 @@ +/* + * linux/arch/arm/mach-footbridge/isa-timer.c + * + * Copyright (C) 1998 Russell King. + * Copyright (C) 1998 Phil Blundell + */ +#include <linux/init.h> +#include <linux/interrupt.h> + +#include <asm/io.h> +#include <asm/irq.h> + +#include <asm/mach/time.h> + +#include "common.h" + +/* + * ISA timer tick support + */ +#define mSEC_10_from_14 ((14318180 + 100) / 200) + +static unsigned long isa_gettimeoffset(void) +{ + int count; + + static int count_p = (mSEC_10_from_14/6); /* for the first call after boot */ + static unsigned long jiffies_p = 0; + + /* + * cache volatile jiffies temporarily; we have IRQs turned off. + */ + unsigned long jiffies_t; + + /* timer count may underflow right here */ + outb_p(0x00, 0x43); /* latch the count ASAP */ + + count = inb_p(0x40); /* read the latched count */ + + /* + * We do this guaranteed double memory access instead of a _p + * postfix in the previous port access. Wheee, hackady hack + */ + jiffies_t = jiffies; + + count |= inb_p(0x40) << 8; + + /* Detect timer underflows. If we haven't had a timer tick since + the last time we were called, and time is apparently going + backwards, the counter must have wrapped during this routine. */ + if ((jiffies_t == jiffies_p) && (count > count_p)) + count -= (mSEC_10_from_14/6); + else + jiffies_p = jiffies_t; + + count_p = count; + + count = (((mSEC_10_from_14/6)-1) - count) * (tick_nsec / 1000); + count = (count + (mSEC_10_from_14/6)/2) / (mSEC_10_from_14/6); + + return count; +} + +static irqreturn_t +isa_timer_interrupt(int irq, void *dev_id, struct pt_regs *regs) +{ + write_seqlock(&xtime_lock); + timer_tick(regs); + write_sequnlock(&xtime_lock); + return IRQ_HANDLED; +} + +static struct irqaction isa_timer_irq = { + .name = "ISA timer tick", + .handler = isa_timer_interrupt, + .flags = SA_INTERRUPT, +}; + +static void __init isa_timer_init(void) +{ + isa_rtc_init(); + + /* enable PIT timer */ + /* set for periodic (4) and LSB/MSB write (0x30) */ + outb(0x34, 0x43); + outb((mSEC_10_from_14/6) & 0xFF, 0x40); + outb((mSEC_10_from_14/6) >> 8, 0x40); + + setup_irq(IRQ_ISA_TIMER, &isa_timer_irq); +} + +struct sys_timer isa_timer = { + .init = isa_timer_init, + .offset = isa_gettimeoffset, +}; |