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Subject[PATCH] linux-2.5.39_timer-changes_A3 (2/3 - bulk move)
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Linus, Dave, all,

This is part 2 of 3 of my timer-change patch. Part 2 is just a bulk
move of code out of time.c and into timer_pit.c and timer_tsc.c. No code
is changed, only moved.

Please note, this code will not compile without the final third part of
this patch collection. This was done for readability alone.

Please apply, along with part 3.

thanks
-john

diff -Nru a/arch/i386/kernel/time.c b/arch/i386/kernel/time.c
--- a/arch/i386/kernel/time.c Mon Sep 30 19:17:48 2002
+++ b/arch/i386/kernel/time.c Mon Sep 30 19:17:48 2002
@@ -73,51 +73,11 @@

unsigned long cpu_khz; /* Detected as we calibrate the TSC */

-/* Number of usecs that the last interrupt was delayed */
-static int delay_at_last_interrupt;
-
-static unsigned long last_tsc_low; /* lsb 32 bits of Time Stamp Counter */
-
-/* Cached *multiplier* to convert TSC counts to microseconds.
- * (see the equation below).
- * Equal to 2^32 * (1 / (clocks per usec) ).
- * Initialized in time_init.
- */
-unsigned long fast_gettimeoffset_quotient;
-
extern rwlock_t xtime_lock;
extern unsigned long wall_jiffies;

spinlock_t rtc_lock = SPIN_LOCK_UNLOCKED;

-static inline unsigned long do_fast_gettimeoffset(void)
-{
- register unsigned long eax, edx;
-
- /* Read the Time Stamp Counter */
-
- rdtsc(eax,edx);
-
- /* .. relative to previous jiffy (32 bits is enough) */
- eax -= last_tsc_low; /* tsc_low delta */
-
- /*
- * Time offset = (tsc_low delta) * fast_gettimeoffset_quotient
- * = (tsc_low delta) * (usecs_per_clock)
- * = (tsc_low delta) * (usecs_per_jiffy / clocks_per_jiffy)
- *
- * Using a mull instead of a divl saves up to 31 clock cycles
- * in the critical path.
- */
-
- __asm__("mull %2"
- :"=a" (eax), "=d" (edx)
- :"rm" (fast_gettimeoffset_quotient),
- "0" (eax));
-
- /* our adjusted time offset in microseconds */
- return delay_at_last_interrupt + edx;
-}

#define TICK_SIZE (tick_nsec / 1000)

@@ -125,104 +85,6 @@
EXPORT_SYMBOL(i8253_lock);

#ifndef CONFIG_X86_TSC
-
-/* This function must be called with interrupts disabled
- * It was inspired by Steve McCanne's microtime-i386 for BSD. -- jrs
- *
- * However, the pc-audio speaker driver changes the divisor so that
- * it gets interrupted rather more often - it loads 64 into the
- * counter rather than 11932! This has an adverse impact on
- * do_gettimeoffset() -- it stops working! What is also not
- * good is that the interval that our timer function gets called
- * is no longer 10.0002 ms, but 9.9767 ms. To get around this
- * would require using a different timing source. Maybe someone
- * could use the RTC - I know that this can interrupt at frequencies
- * ranging from 8192Hz to 2Hz. If I had the energy, I'd somehow fix
- * it so that at startup, the timer code in sched.c would select
- * using either the RTC or the 8253 timer. The decision would be
- * based on whether there was any other device around that needed
- * to trample on the 8253. I'd set up the RTC to interrupt at 1024 Hz,
- * and then do some jiggery to have a version of do_timer that
- * advanced the clock by 1/1024 s. Every time that reached over 1/100
- * of a second, then do all the old code. If the time was kept correct
- * then do_gettimeoffset could just return 0 - there is no low order
- * divider that can be accessed.
- *
- * Ideally, you would be able to use the RTC for the speaker driver,
- * but it appears that the speaker driver really needs interrupt more
- * often than every 120 us or so.
- *
- * Anyway, this needs more thought.... pjsg (1993-08-28)
- *
- * If you are really that interested, you should be reading
- * comp.protocols.time.ntp!
- */
-
-static unsigned long do_slow_gettimeoffset(void)
-{
- int count;
-
- static int count_p = LATCH; /* 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;
-
- /* gets recalled with irq locally disabled */
- spin_lock(&i8253_lock);
- /* 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;
-
- /* VIA686a test code... reset the latch if count > max + 1 */
- if (count > LATCH) {
- outb_p(0x34, 0x43);
- outb_p(LATCH & 0xff, 0x40);
- outb(LATCH >> 8, 0x40);
- count = LATCH - 1;
- }
-
- spin_unlock(&i8253_lock);
-
- /*
- * avoiding timer inconsistencies (they are rare, but they happen)...
- * there are two kinds of problems that must be avoided here:
- * 1. the timer counter underflows
- * 2. hardware problem with the timer, not giving us continuous time,
- * the counter does small "jumps" upwards on some Pentium systems,
- * (see c't 95/10 page 335 for Neptun bug.)
- */
-
-
- if( jiffies_t == jiffies_p ) {
- if( count > count_p ) {
- /* the nutcase */
- count = do_timer_overflow(count);
- }
- } else
- jiffies_p = jiffies_t;
-
- count_p = count;
-
- count = ((LATCH-1) - count) * TICK_SIZE;
- count = (count + LATCH/2) / LATCH;
-
- return count;
-}
-
-static unsigned long (*do_gettimeoffset)(void) = do_slow_gettimeoffset;
-
#else

#define do_gettimeoffset() do_fast_gettimeoffset()
@@ -433,34 +295,7 @@
*/
write_lock(&xtime_lock);

- if (use_tsc)
- {
- /*
- * It is important that these two operations happen almost at
- * the same time. We do the RDTSC stuff first, since it's
- * faster. To avoid any inconsistencies, we need interrupts
- * disabled locally.
- */
-
- /*
- * Interrupts are just disabled locally since the timer irq
- * has the SA_INTERRUPT flag set. -arca
- */

- /* read Pentium cycle counter */
-
- rdtscl(last_tsc_low);
-
- spin_lock(&i8253_lock);
- outb_p(0x00, 0x43); /* latch the count ASAP */
-
- count = inb_p(0x40); /* read the latched count */
- count |= inb(0x40) << 8;
- spin_unlock(&i8253_lock);
-
- count = ((LATCH-1) - count) * TICK_SIZE;
- delay_at_last_interrupt = (count + LATCH/2) / LATCH;
- }

do_timer_interrupt(irq, NULL, regs);

@@ -510,85 +345,6 @@
return mktime(year, mon, day, hour, min, sec);
}

-/* ------ Calibrate the TSC -------
- * Return 2^32 * (1 / (TSC clocks per usec)) for do_fast_gettimeoffset().
- * Too much 64-bit arithmetic here to do this cleanly in C, and for
- * accuracy's sake we want to keep the overhead on the CTC speaker (channel 2)
- * output busy loop as low as possible. We avoid reading the CTC registers
- * directly because of the awkward 8-bit access mechanism of the 82C54
- * device.
- */
-
-#define CALIBRATE_LATCH (5 * LATCH)
-#define CALIBRATE_TIME (5 * 1000020/HZ)
-
-#ifdef CONFIG_X86_TSC
-static unsigned long __init calibrate_tsc(void)
-{
- /* Set the Gate high, disable speaker */
- outb((inb(0x61) & ~0x02) | 0x01, 0x61);
-
- /*
- * Now let's take care of CTC channel 2
- *
- * Set the Gate high, program CTC channel 2 for mode 0,
- * (interrupt on terminal count mode), binary count,
- * load 5 * LATCH count, (LSB and MSB) to begin countdown.
- */
- outb(0xb0, 0x43); /* binary, mode 0, LSB/MSB, Ch 2 */
- outb(CALIBRATE_LATCH & 0xff, 0x42); /* LSB of count */
- outb(CALIBRATE_LATCH >> 8, 0x42); /* MSB of count */
-
- {
- unsigned long startlow, starthigh;
- unsigned long endlow, endhigh;
- unsigned long count;
-
- rdtsc(startlow,starthigh);
- count = 0;
- do {
- count++;
- } while ((inb(0x61) & 0x20) == 0);
- rdtsc(endlow,endhigh);
-
- last_tsc_low = endlow;
-
- /* Error: ECTCNEVERSET */
- if (count <= 1)
- goto bad_ctc;
-
- /* 64-bit subtract - gcc just messes up with long longs */
- __asm__("subl %2,%0\n\t"
- "sbbl %3,%1"
- :"=a" (endlow), "=d" (endhigh)
- :"g" (startlow), "g" (starthigh),
- "0" (endlow), "1" (endhigh));
-
- /* Error: ECPUTOOFAST */
- if (endhigh)
- goto bad_ctc;
-
- /* Error: ECPUTOOSLOW */
- if (endlow <= CALIBRATE_TIME)
- goto bad_ctc;
-
- __asm__("divl %2"
- :"=a" (endlow), "=d" (endhigh)
- :"r" (endlow), "0" (0), "1" (CALIBRATE_TIME));
-
- return endlow;
- }
-
- /*
- * The CTC wasn't reliable: we got a hit on the very first read,
- * or the CPU was so fast/slow that the quotient wouldn't fit in
- * 32 bits..
- */
-bad_ctc:
- return 0;
-}
-#endif /* CONFIG_X86_TSC */
-
static struct sys_device device_i8253 = {
.name = "rtc",
.id = 0,
@@ -605,119 +361,12 @@
device_initcall(time_init_device);


-#ifdef CONFIG_CPU_FREQ
-
-static int
-time_cpufreq_notifier(struct notifier_block *nb, unsigned long val,
- void *data)
-{
- struct cpufreq_freqs *freq = data;
- unsigned int i;
-
- if (!cpu_has_tsc)
- return 0;
-
- switch (val) {
- case CPUFREQ_PRECHANGE:
- if ((freq->old < freq->new) &&
- ((freq->cpu == CPUFREQ_ALL_CPUS) || (freq->cpu == 0))) {
- cpu_khz = cpufreq_scale(cpu_khz, freq->old, freq->new);
- fast_gettimeoffset_quotient = cpufreq_scale(fast_gettimeoffset_quotient, freq->new, freq->old);
- }
- for (i=0; i<NR_CPUS; i++)
- if ((freq->cpu == CPUFREQ_ALL_CPUS) || (freq->cpu == i))
- cpu_data[i].loops_per_jiffy = cpufreq_scale(cpu_data[i].loops_per_jiffy, freq->old, freq->new);
- break;
-
- case CPUFREQ_POSTCHANGE:
- if ((freq->new < freq->old) &&
- ((freq->cpu == CPUFREQ_ALL_CPUS) || (freq->cpu == 0))) {
- cpu_khz = cpufreq_scale(cpu_khz, freq->old, freq->new);
- fast_gettimeoffset_quotient = cpufreq_scale(fast_gettimeoffset_quotient, freq->new, freq->old);
- }
- for (i=0; i<NR_CPUS; i++)
- if ((freq->cpu == CPUFREQ_ALL_CPUS) || (freq->cpu == i))
- cpu_data[i].loops_per_jiffy = cpufreq_scale(cpu_data[i].loops_per_jiffy, freq->old, freq->new);
- break;
- }
-
- return 0;
-}
-
-static struct notifier_block time_cpufreq_notifier_block = {
- notifier_call: time_cpufreq_notifier
-};
-#endif
-
-
void __init time_init(void)
{
-#ifdef CONFIG_X86_TSC
- extern int x86_udelay_tsc;
-#endif

xtime.tv_sec = get_cmos_time();
xtime.tv_nsec = 0;

-/*
- * If we have APM enabled or the CPU clock speed is variable
- * (CPU stops clock on HLT or slows clock to save power)
- * then the TSC timestamps may diverge by up to 1 jiffy from
- * 'real time' but nothing will break.
- * The most frequent case is that the CPU is "woken" from a halt
- * state by the timer interrupt itself, so we get 0 error. In the
- * rare cases where a driver would "wake" the CPU and request a
- * timestamp, the maximum error is < 1 jiffy. But timestamps are
- * still perfectly ordered.
- * Note that the TSC counter will be reset if APM suspends
- * to disk; this won't break the kernel, though, 'cuz we're
- * smart. See arch/i386/kernel/apm.c.
- */
-#ifdef CONFIG_X86_TSC
- /*
- * Firstly we have to do a CPU check for chips with
- * a potentially buggy TSC. At this point we haven't run
- * the ident/bugs checks so we must run this hook as it
- * may turn off the TSC flag.
- *
- * NOTE: this doesnt yet handle SMP 486 machines where only
- * some CPU's have a TSC. Thats never worked and nobody has
- * moaned if you have the only one in the world - you fix it!
- */
-
- dodgy_tsc();
-
- if (cpu_has_tsc) {
- unsigned long tsc_quotient = calibrate_tsc();
- if (tsc_quotient) {
- fast_gettimeoffset_quotient = tsc_quotient;
- use_tsc = 1;
- /*
- * We could be more selective here I suspect
- * and just enable this for the next intel chips ?
- */
- x86_udelay_tsc = 1;
-#ifndef do_gettimeoffset
- do_gettimeoffset = do_fast_gettimeoffset;
-#endif
-
- /* report CPU clock rate in Hz.
- * The formula is (10^6 * 2^32) / (2^32 * 1 / (clocks/us)) =
- * clock/second. Our precision is about 100 ppm.
- */
- { unsigned long eax=0, edx=1000;
- __asm__("divl %2"
- :"=a" (cpu_khz), "=d" (edx)
- :"r" (tsc_quotient),
- "0" (eax), "1" (edx));
- printk("Detected %lu.%03lu MHz processor.\n", cpu_khz / 1000, cpu_khz % 1000);
- }
-#ifdef CONFIG_CPU_FREQ
- cpufreq_register_notifier(&time_cpufreq_notifier_block, CPUFREQ_TRANSITION_NOTIFIER);
-#endif
- }
- }
-#endif /* CONFIG_X86_TSC */

time_init_hook();
}
diff -Nru a/arch/i386/kernel/timer_pit.c b/arch/i386/kernel/timer_pit.c
--- /dev/null Wed Dec 31 16:00:00 1969
+++ b/arch/i386/kernel/timer_pit.c Mon Sep 30 19:17:48 2002
@@ -0,0 +1,97 @@
+
+/* This function must be called with interrupts disabled
+ * It was inspired by Steve McCanne's microtime-i386 for BSD. -- jrs
+ *
+ * However, the pc-audio speaker driver changes the divisor so that
+ * it gets interrupted rather more often - it loads 64 into the
+ * counter rather than 11932! This has an adverse impact on
+ * do_gettimeoffset() -- it stops working! What is also not
+ * good is that the interval that our timer function gets called
+ * is no longer 10.0002 ms, but 9.9767 ms. To get around this
+ * would require using a different timing source. Maybe someone
+ * could use the RTC - I know that this can interrupt at frequencies
+ * ranging from 8192Hz to 2Hz. If I had the energy, I'd somehow fix
+ * it so that at startup, the timer code in sched.c would select
+ * using either the RTC or the 8253 timer. The decision would be
+ * based on whether there was any other device around that needed
+ * to trample on the 8253. I'd set up the RTC to interrupt at 1024 Hz,
+ * and then do some jiggery to have a version of do_timer that
+ * advanced the clock by 1/1024 s. Every time that reached over 1/100
+ * of a second, then do all the old code. If the time was kept correct
+ * then do_gettimeoffset could just return 0 - there is no low order
+ * divider that can be accessed.
+ *
+ * Ideally, you would be able to use the RTC for the speaker driver,
+ * but it appears that the speaker driver really needs interrupt more
+ * often than every 120 us or so.
+ *
+ * Anyway, this needs more thought.... pjsg (1993-08-28)
+ *
+ * If you are really that interested, you should be reading
+ * comp.protocols.time.ntp!
+ */
+
+static unsigned long do_slow_gettimeoffset(void)
+{
+ int count;
+
+ static int count_p = LATCH; /* 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;
+
+ /* gets recalled with irq locally disabled */
+ spin_lock(&i8253_lock);
+ /* 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;
+
+ /* VIA686a test code... reset the latch if count > max + 1 */
+ if (count > LATCH) {
+ outb_p(0x34, 0x43);
+ outb_p(LATCH & 0xff, 0x40);
+ outb(LATCH >> 8, 0x40);
+ count = LATCH - 1;
+ }
+
+ spin_unlock(&i8253_lock);
+
+ /*
+ * avoiding timer inconsistencies (they are rare, but they happen)...
+ * there are two kinds of problems that must be avoided here:
+ * 1. the timer counter underflows
+ * 2. hardware problem with the timer, not giving us continuous time,
+ * the counter does small "jumps" upwards on some Pentium systems,
+ * (see c't 95/10 page 335 for Neptun bug.)
+ */
+
+
+ if( jiffies_t == jiffies_p ) {
+ if( count > count_p ) {
+ /* the nutcase */
+ count = do_timer_overflow(count);
+ }
+ } else
+ jiffies_p = jiffies_t;
+
+ count_p = count;
+
+ count = ((LATCH-1) - count) * TICK_SIZE;
+ count = (count + LATCH/2) / LATCH;
+
+ return count;
+}
+
+static unsigned long (*do_gettimeoffset)(void) = do_slow_gettimeoffset;
diff -Nru a/arch/i386/kernel/timer_tsc.c b/arch/i386/kernel/timer_tsc.c
--- /dev/null Wed Dec 31 16:00:00 1969
+++ b/arch/i386/kernel/timer_tsc.c Mon Sep 30 19:17:48 2002
@@ -0,0 +1,262 @@
+/* Number of usecs that the last interrupt was delayed */
+static int delay_at_last_interrupt;
+
+static unsigned long last_tsc_low; /* lsb 32 bits of Time Stamp Counter */
+
+/* Cached *multiplier* to convert TSC counts to microseconds.
+ * (see the equation below).
+ * Equal to 2^32 * (1 / (clocks per usec) ).
+ * Initialized in time_init.
+ */
+unsigned long fast_gettimeoffset_quotient;
+
+static inline unsigned long do_fast_gettimeoffset(void)
+{
+ register unsigned long eax, edx;
+
+ /* Read the Time Stamp Counter */
+
+ rdtsc(eax,edx);
+
+ /* .. relative to previous jiffy (32 bits is enough) */
+ eax -= last_tsc_low; /* tsc_low delta */
+
+ /*
+ * Time offset = (tsc_low delta) * fast_gettimeoffset_quotient
+ * = (tsc_low delta) * (usecs_per_clock)
+ * = (tsc_low delta) * (usecs_per_jiffy / clocks_per_jiffy)
+ *
+ * Using a mull instead of a divl saves up to 31 clock cycles
+ * in the critical path.
+ */
+
+ __asm__("mull %2"
+ :"=a" (eax), "=d" (edx)
+ :"rm" (fast_gettimeoffset_quotient),
+ "0" (eax));
+
+ /* our adjusted time offset in microseconds */
+ return delay_at_last_interrupt + edx;
+}
+
+
+
+if (use_tsc)
+ {
+ /*
+ * It is important that these two operations happen almost at
+ * the same time. We do the RDTSC stuff first, since it's
+ * faster. To avoid any inconsistencies, we need interrupts
+ * disabled locally.
+ */
+
+ /*
+ * Interrupts are just disabled locally since the timer irq
+ * has the SA_INTERRUPT flag set. -arca
+ */
+
+ /* read Pentium cycle counter */
+
+ rdtscl(last_tsc_low);
+
+ spin_lock(&i8253_lock);
+ outb_p(0x00, 0x43); /* latch the count ASAP */
+
+ count = inb_p(0x40); /* read the latched count */
+ count |= inb(0x40) << 8;
+ spin_unlock(&i8253_lock);
+
+ count = ((LATCH-1) - count) * TICK_SIZE;
+ delay_at_last_interrupt = (count + LATCH/2) / LATCH;
+ }
+
+
+/* ------ Calibrate the TSC -------
+ * Return 2^32 * (1 / (TSC clocks per usec)) for do_fast_gettimeoffset().
+ * Too much 64-bit arithmetic here to do this cleanly in C, and for
+ * accuracy's sake we want to keep the overhead on the CTC speaker (channel 2)
+ * output busy loop as low as possible. We avoid reading the CTC registers
+ * directly because of the awkward 8-bit access mechanism of the 82C54
+ * device.
+ */
+
+#define CALIBRATE_LATCH (5 * LATCH)
+#define CALIBRATE_TIME (5 * 1000020/HZ)
+
+#ifdef CONFIG_X86_TSC
+static unsigned long __init calibrate_tsc(void)
+{
+ /* Set the Gate high, disable speaker */
+ outb((inb(0x61) & ~0x02) | 0x01, 0x61);
+
+ /*
+ * Now let's take care of CTC channel 2
+ *
+ * Set the Gate high, program CTC channel 2 for mode 0,
+ * (interrupt on terminal count mode), binary count,
+ * load 5 * LATCH count, (LSB and MSB) to begin countdown.
+ */
+ outb(0xb0, 0x43); /* binary, mode 0, LSB/MSB, Ch 2 */
+ outb(CALIBRATE_LATCH & 0xff, 0x42); /* LSB of count */
+ outb(CALIBRATE_LATCH >> 8, 0x42); /* MSB of count */
+
+ {
+ unsigned long startlow, starthigh;
+ unsigned long endlow, endhigh;
+ unsigned long count;
+
+ rdtsc(startlow,starthigh);
+ count = 0;
+ do {
+ count++;
+ } while ((inb(0x61) & 0x20) == 0);
+ rdtsc(endlow,endhigh);
+
+ last_tsc_low = endlow;
+
+ /* Error: ECTCNEVERSET */
+ if (count <= 1)
+ goto bad_ctc;
+
+ /* 64-bit subtract - gcc just messes up with long longs */
+ __asm__("subl %2,%0\n\t"
+ "sbbl %3,%1"
+ :"=a" (endlow), "=d" (endhigh)
+ :"g" (startlow), "g" (starthigh),
+ "0" (endlow), "1" (endhigh));
+
+ /* Error: ECPUTOOFAST */
+ if (endhigh)
+ goto bad_ctc;
+
+ /* Error: ECPUTOOSLOW */
+ if (endlow <= CALIBRATE_TIME)
+ goto bad_ctc;
+
+ __asm__("divl %2"
+ :"=a" (endlow), "=d" (endhigh)
+ :"r" (endlow), "0" (0), "1" (CALIBRATE_TIME));
+
+ return endlow;
+ }
+
+ /*
+ * The CTC wasn't reliable: we got a hit on the very first read,
+ * or the CPU was so fast/slow that the quotient wouldn't fit in
+ * 32 bits..
+ */
+bad_ctc:
+ return 0;
+}
+#endif /* CONFIG_X86_TSC */
+
+
+#ifdef CONFIG_CPU_FREQ
+
+static int
+time_cpufreq_notifier(struct notifier_block *nb, unsigned long val,
+ void *data)
+{
+ struct cpufreq_freqs *freq = data;
+ unsigned int i;
+
+ if (!cpu_has_tsc)
+ return 0;
+
+ switch (val) {
+ case CPUFREQ_PRECHANGE:
+ if ((freq->old < freq->new) &&
+ ((freq->cpu == CPUFREQ_ALL_CPUS) || (freq->cpu == 0))) {
+ cpu_khz = cpufreq_scale(cpu_khz, freq->old, freq->new);
+ fast_gettimeoffset_quotient = cpufreq_scale(fast_gettimeoffset_quotient, freq->new, freq->old);
+ }
+ for (i=0; i<NR_CPUS; i++)
+ if ((freq->cpu == CPUFREQ_ALL_CPUS) || (freq->cpu == i))
+ cpu_data[i].loops_per_jiffy = cpufreq_scale(cpu_data[i].loops_per_jiffy, freq->old, freq->new);
+ break;
+
+ case CPUFREQ_POSTCHANGE:
+ if ((freq->new < freq->old) &&
+ ((freq->cpu == CPUFREQ_ALL_CPUS) || (freq->cpu == 0))) {
+ cpu_khz = cpufreq_scale(cpu_khz, freq->old, freq->new);
+ fast_gettimeoffset_quotient = cpufreq_scale(fast_gettimeoffset_quotient, freq->new, freq->old);
+ }
+ for (i=0; i<NR_CPUS; i++)
+ if ((freq->cpu == CPUFREQ_ALL_CPUS) || (freq->cpu == i))
+ cpu_data[i].loops_per_jiffy = cpufreq_scale(cpu_data[i].loops_per_jiffy, freq->old, freq->new);
+ break;
+ }
+
+ return 0;
+}
+
+static struct notifier_block time_cpufreq_notifier_block = {
+ notifier_call: time_cpufreq_notifier
+};
+#endif
+
+
+
+#ifdef CONFIG_X86_TSC
+ extern int x86_udelay_tsc;
+#endif
+
+/*
+ * If we have APM enabled or the CPU clock speed is variable
+ * (CPU stops clock on HLT or slows clock to save power)
+ * then the TSC timestamps may diverge by up to 1 jiffy from
+ * 'real time' but nothing will break.
+ * The most frequent case is that the CPU is "woken" from a halt
+ * state by the timer interrupt itself, so we get 0 error. In the
+ * rare cases where a driver would "wake" the CPU and request a
+ * timestamp, the maximum error is < 1 jiffy. But timestamps are
+ * still perfectly ordered.
+ * Note that the TSC counter will be reset if APM suspends
+ * to disk; this won't break the kernel, though, 'cuz we're
+ * smart. See arch/i386/kernel/apm.c.
+ */
+#ifdef CONFIG_X86_TSC
+ /*
+ * Firstly we have to do a CPU check for chips with
+ * a potentially buggy TSC. At this point we haven't run
+ * the ident/bugs checks so we must run this hook as it
+ * may turn off the TSC flag.
+ *
+ * NOTE: this doesnt yet handle SMP 486 machines where only
+ * some CPU's have a TSC. Thats never worked and nobody has
+ * moaned if you have the only one in the world - you fix it!
+ */
+
+ dodgy_tsc();
+
+ if (cpu_has_tsc) {
+ unsigned long tsc_quotient = calibrate_tsc();
+ if (tsc_quotient) {
+ fast_gettimeoffset_quotient = tsc_quotient;
+ use_tsc = 1;
+ /*
+ * We could be more selective here I suspect
+ * and just enable this for the next intel chips ?
+ */
+ x86_udelay_tsc = 1;
+#ifndef do_gettimeoffset
+ do_gettimeoffset = do_fast_gettimeoffset;
+#endif
+
+ /* report CPU clock rate in Hz.
+ * The formula is (10^6 * 2^32) / (2^32 * 1 / (clocks/us)) =
+ * clock/second. Our precision is about 100 ppm.
+ */
+ { unsigned long eax=0, edx=1000;
+ __asm__("divl %2"
+ :"=a" (cpu_khz), "=d" (edx)
+ :"r" (tsc_quotient),
+ "0" (eax), "1" (edx));
+ printk("Detected %lu.%03lu MHz processor.\n", cpu_khz / 1000, cpu_khz % 1000);
+ }
+#ifdef CONFIG_CPU_FREQ
+ cpufreq_register_notifier(&time_cpufreq_notifier_block, CPUFREQ_TRANSITION_NOTIFIER);
+#endif
+ }
+ }
+#endif /* CONFIG_X86_TSC */
-
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