i386 timer changes for 2.5.41

Hi Linus,

I've taken the i386 timer.c patches that John Stultz has been working on for a while, made some minor tweaks, added them to a bk tree, and tested them on all the boxes that I have access too. Here's the resulting changesets:

Please pull from bk://lsm.bkbits.net/timer-2.5

These split up the time.c code to handle different interrupt time sources, moving the code into a new arck/i386/kernel/timers directory. This is going to get more important as new timer sources become available (like IBM's Summit chipset), and removes a lot of #ifdefs from the existing code.

The differences from John's last patches are:
- use bk to show the history of the time.c file moves
- added proper documentation for struct timer_opts
- init() in timer_opts now returns 0 for success
- timer array is now static, and NULL terminated to make adding new sources an easier patch.

thanks,

greg k-h

 arch/i386/Makefile                  |    2 
 arch/i386/kernel/time.c             |  374 -----------------------------------
 arch/i386/kernel/timers/Makefile    |   10 
 arch/i386/kernel/timers/timer.c     |   39 +++
 arch/i386/kernel/timers/timer_pit.c |  132 ++++++++++++
 arch/i386/kernel/timers/timer_tsc.c |  382 +++++++++++++++++++++++++++++++-----
 include/asm-i386/timer.h            |   22 ++
 7 files changed, 538 insertions(+), 423 deletions(-)

-----

[email protected], 2002-10-10 01:10:45-07:00, [email protected]
i386 timer core: intergrate the new timer code to use the two different timer files.

 arch/i386/Makefile                  |    2 
 arch/i386/kernel/time.c             |   23 ++----
 arch/i386/kernel/timers/Makefile    |   10 +++
 arch/i386/kernel/timers/timer.c     |    8 +-
 arch/i386/kernel/timers/timer_pit.c |   35 +++++++++-
 arch/i386/kernel/timers/timer_tsc.c |  120 ++++++++++++++++++++----------------
 include/asm-i386/timer.h            |    2 
 7 files changed, 128 insertions(+), 72 deletions(-)

------

[email protected], 2002-10-10 00:08:03-07:00, [email protected]
i386 timer core: move code out of time.c into timers/timer_pit.c and timers/timer_tsc.c

 arch/i386/kernel/time.c             |  351 ------------------------------------
 arch/i386/kernel/timers/timer_pit.c |   97 +++++++++
 arch/i386/kernel/timers/timer_tsc.c |  262 ++++++++++++++++++++++++++
 3 files changed, 359 insertions(+), 351 deletions(-)

------

[email protected], 2002-10-09 23:57:56-07:00, [email protected]
i386 timer core: introduce struct timer_ops

provides the infrastructure needed via the timer_ops structure, as well as the select_timer() function for choosing the best available timer

 arch/i386/kernel/timers/timer.c |   31 +++++++++++++++++++++++++++++++
 include/asm-i386/timer.h        |   20 ++++++++++++++++++++
 2 files changed, 51 insertions(+)

------

# This is a BitKeeper generated patch for the following project:
# Project Name: Linux kernel tree
# This patch format is intended for GNU patch command version 2.5 or higher. # This patch includes the following deltas:

#	           ChangeSet	1.748   -> 1.749  
#	               (new)	        -> 1.1     include/asm-i386/timer.h
#	               (new)	        -> 1.1     arch/i386/kernel/timers/timer.c

#
# The following is the BitKeeper ChangeSet Log
# --------------------------------------------
# 02/10/09 [email protected] 1.749

# i386 timer core: introduce struct timer_ops
# 
# provides the infrastructure needed via the timer_ops structure, 
# as well as the select_timer() function for choosing the best 
# available timer
# --------------------------------------------
#
diff -Nru a/arch/i386/kernel/timers/timer.c b/arch/i386/kernel/timers/timer.c
--- /dev/null	Wed Dec 31 16:00:00 1969
+++ b/arch/i386/kernel/timers/timer.c	Thu Oct 10 11:21:16 2002
@@ -0,0 +1,31 @@
+#include <linux/kernel.h>
+#include <asm/timer.h>
+
+/* list of externed timers */
+/* eg: extern struct timer_opts timer_XXX*/;
+
+/* list of timers, ordered by preference, NULL terminated */
+static struct timer_opts* timers[] = {
+	/* eg: &timer_XXX */
+	NULL,
+};
+
+
+/* iterates through the list of timers, returning the first 
+ * one that initializes successfully.
+ */
+struct timer_opts* select_timer(void)
+{
+	int i = 0;
+	
+	/* find most preferred working timer */
+	while (timers[i]) {
+		if (timers[i]->init)
+			if (timers[i]->init() == 0)
+				return timers[i];
+		++i;
+	}
+		
+	panic("select_timer: Cannot find a suitable timer\n");
+	return NULL;
+}
diff -Nru a/include/asm-i386/timer.h b/include/asm-i386/timer.h
--- /dev/null	Wed Dec 31 16:00:00 1969
+++ b/include/asm-i386/timer.h	Thu Oct 10 11:21:16 2002
@@ -0,0 +1,20 @@
+#ifndef _ASMi386_TIMER_H
+#define _ASMi386_TIMER_H
+
+/**
+ * struct timer_ops - used to define a timer source
+ *
+ * @init: Probes and initializes the timer.  Returns 0 on success, anything
+ *	else on failure.
+ * @mark_offset: called by the timer interrupt
+ * @get_offset: called by gettimeofday().  Returns the number of ms since the
+ *	last timer intruupt.
+ */
+struct timer_opts{
+	int (*init)(void);
+	void (*mark_offset)(void);
+	unsigned long (*get_offset)(void);
+};
+
+extern struct timer_opts* select_timer(void);
+#endif

Note, this patch is messy. If you look at the bk changeset you will see that no new code is added, but time.c is copied to timer_pit.c and timer_tsc.c, and then code is taken away from those files.

# This is a BitKeeper generated patch for the following project:
# Project Name: Linux kernel tree
# This patch format is intended for GNU patch command version 2.5 or higher. # This patch includes the following deltas:
# ChangeSet 1.749 -> 1.750
# arch/i386/kernel/time.c 1.16 -> 1.17

#	               (new)	        -> 1.18    arch/i386/kernel/timers/timer_pit.c
#	               (new)	        -> 1.18    arch/i386/kernel/timers/timer_tsc.c

#
# The following is the BitKeeper ChangeSet Log
# --------------------------------------------
# 02/10/10 [email protected] 1.750

# i386 timer core: move code out of time.c into timers/timer_pit.c and timers/timer_tsc.c
# --------------------------------------------
#
diff -Nru a/arch/i386/kernel/time.c b/arch/i386/kernel/time.c
--- a/arch/i386/kernel/time.c	Thu Oct 10 11:21:13 2002
+++ b/arch/i386/kernel/time.c	Thu Oct 10 11:21:13 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/timers/timer_pit.c b/arch/i386/kernel/timers/timer_pit.c
@@ -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;

# This is a BitKeeper generated patch for the following project:
# Project Name: Linux kernel tree
# This patch format is intended for GNU patch command version 2.5 or higher. # This patch includes the following deltas:
# ChangeSet 1.750 -> 1.751
# include/asm-i386/timer.h 1.1 -> 1.2
# arch/i386/kernel/timers/timer.c 1.1 -> 1.2
# arch/i386/Makefile 1.19 -> 1.20
# arch/i386/kernel/time.c 1.17 -> 1.18
# arch/i386/kernel/timers/timer_pit.c 1.18 -> 1.19
# arch/i386/kernel/timers/timer_tsc.c 1.18 -> 1.19
# (new) -> 1.1 arch/i386/kernel/timers/Makefile
#
# The following is the BitKeeper ChangeSet Log
# --------------------------------------------
# 02/10/10 [email protected] 1.751

# i386 timer core: intergrate the new timer code to use the two different timer files.
# --------------------------------------------
#
diff -Nru a/arch/i386/Makefile b/arch/i386/Makefile
--- a/arch/i386/Makefile	Thu Oct 10 11:21:10 2002
+++ b/arch/i386/Makefile	Thu Oct 10 11:21:10 2002
@@ -53,7 +53,7 @@

libs-y += arch/i386/lib/
core-y += arch/i386/kernel/ arch/i386/mm/ \
- arch/i386/$(MACHINE)/
+ arch/i386/$(MACHINE)/ arch/i386/kernel/timers/
drivers-$(CONFIG_MATH_EMULATION) += arch/i386/math-emu/
drivers-$(CONFIG_PCI) += arch/i386/pci/

diff -Nru a/arch/i386/kernel/time.c b/arch/i386/kernel/time.c
@@ -53,6 +53,7 @@
 #include <asm/mpspec.h>
 #include <asm/uaccess.h>
 #include <asm/processor.h>
+#include <asm/timer.h>
 
 #include <linux/mc146818rtc.h>
 #include <linux/timex.h>

@@ -78,18 +79,10 @@
 
 spinlock_t rtc_lock = SPIN_LOCK_UNLOCKED;
 
-
-#define TICK_SIZE (tick_nsec / 1000)
-
 spinlock_t i8253_lock = SPIN_LOCK_UNLOCKED;
 EXPORT_SYMBOL(i8253_lock);
 
-#ifndef CONFIG_X86_TSC
-#else
-
-#define do_gettimeoffset()	do_fast_gettimeoffset()
-
-#endif
+struct timer_opts* timer;
 
 /*
  * This version of gettimeofday has microsecond resolution

@@ -101,7 +94,7 @@
 	unsigned long usec, sec;
 
 	read_lock_irqsave(&xtime_lock, flags);
-	usec = do_gettimeoffset();
+	usec = timer->get_offset();
 	{
 		unsigned long lost = jiffies - wall_jiffies;
 		if (lost)

@@ -129,7 +122,7 @@
 	 * wall time.  Discover what correction gettimeofday() would have
 	 * made, and then undo it!
 	 */
-	tv->tv_usec -= do_gettimeoffset();
+	tv->tv_usec -= timer->get_offset();
 	tv->tv_usec -= (jiffies - wall_jiffies) * (1000000 / HZ);
 
 	while (tv->tv_usec < 0) {

@@ -275,8 +268,6 @@
 #endif
 }
 
-static int use_tsc;
-
 /*
  * This is the same as the above, except we _also_ save the current
  * Time Stamp Counter value at the time of the timer interrupt, so that

@@ -284,8 +275,6 @@
  */
 void timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
 {
-	int count;
-
 	/*
 	 * Here we are in the timer irq handler. We just have irqs locally
 	 * disabled but we don't know if the timer_bh is running on the other

@@ -295,7 +284,7 @@
 	 */
 	write_lock(&xtime_lock);
 
-	
+	timer->mark_offset();
  
 	do_timer_interrupt(irq, NULL, regs);
 

@@ -345,6 +334,7 @@
 	return mktime(year, mon, day, hour, min, sec);
 }
 
+/* XXX this driverfs stuff should probably go elsewhere later -john */
 static struct sys_device device_i8253 = {
 	.name		= "rtc",
 	.id		= 0,

@@ -368,5 +358,6 @@
 	xtime.tv_nsec = 0;
 
 
+	timer = select_timer();
 	time_init_hook();
 }

diff -Nru a/arch/i386/kernel/timers/Makefile b/arch/i386/kernel/timers/Makefile
@@ -0,0 +1,10 @@
+#
+# Makefile for x86 timers
+#
+
+obj-y := timer.o
+
+obj-y += timer_tsc.o
+obj-y += timer_pit.o
+
+include $(TOPDIR)/Rules.make

diff -Nru a/arch/i386/kernel/timers/timer.c b/arch/i386/kernel/timers/timer.c
@@ -2,11 +2,15 @@
 #include <asm/timer.h>
 
 /* list of externed timers */
-/* eg: extern struct timer_opts timer_XXX*/;
+extern struct timer_opts timer_pit;
+extern struct timer_opts timer_tsc;
 
 /* list of timers, ordered by preference, NULL terminated */
 static struct timer_opts* timers[] = {
-	/* eg: &timer_XXX */
+	&timer_tsc,
+#ifndef CONFIG_X86_TSC
+	&timer_pit,
+#endif
 	NULL,
 };
 

diff -Nru a/arch/i386/kernel/timers/timer_pit.c b/arch/i386/kernel/timers/timer_pit.c
@@ -1,3 +1,28 @@
+/*
+ * This code largely moved from arch/i386/kernel/time.c.
+ * See comments there for proper credits.
+ */
+
+#include <linux/spinlock.h>
+#include <linux/module.h>
+#include <linux/device.h>
+#include <asm/timer.h>
+#include <asm/io.h>
+
+extern spinlock_t i8259A_lock;
+extern spinlock_t i8253_lock;
+#include "do_timer.h"
+
+static int init_pit(void)
+{
+	return 0;
+}
+
+static void mark_offset_pit(void)
+{
+	/* nothing needed */
+}
+
 
 /* This function must be called with interrupts disabled 
  * It was inspired by Steve McCanne's microtime-i386 for BSD.  -- jrs

@@ -31,7 +56,7 @@
  * comp.protocols.time.ntp!
  */
 
-static unsigned long do_slow_gettimeoffset(void)
+static unsigned long get_offset_pit(void)
 {
 	int count;
 

@@ -94,4 +119,10 @@
 	return count;
 }
 
-static unsigned long (*do_gettimeoffset)(void) = do_slow_gettimeoffset;
+
+/* tsc timer_opts struct */
+struct timer_opts timer_pit = {
+	.init =		init_pit, 
+	.mark_offset =	mark_offset_pit, 
+	.get_offset =	get_offset_pit,
+};

diff -Nru a/include/asm-i386/timer.h b/include/asm-i386/timer.h
@@ -16,5 +16,7 @@
 	unsigned long (*get_offset)(void);
 };
 
+#define TICK_SIZE (tick_nsec / 1000)
+
 extern struct timer_opts* select_timer(void);
 #endif

Hmm, I was getting to them anyway, this would make it easier.

Except for the fact that I get

[torvalds@penguin linux]$ bk pull bk://lsm.bkbits.net/timer-2.5 ERROR-cannot cd to timer-2.5 (illegal, nonexistant, or not package root)

when I try to check it out..

Linus

I ended up just importing it from the patches I had pending anyway. Including the Cyclone code, although I removed the Config.in entry to make sure nobody even tries to enable it until the rest of the summit code is there.

Linus

Thanks for doing this.

Here's a patch against your latest bk tree, that contains the cleanups I did to John's patches. It does the following:
- removes a few compiler warnings from time.c
- uses C99 initializers
- makes the timer list static
- adds better documentation to the timer function structure
- makes the timer init function return 0 on success
- NULL terminates the list of timers to make further patches easier.

I can put this in a bk tree for you to pull, but I thought a simple patch would be easier.

thanks,

greg k-h

diff -Naur -X ../dontdiff timer2-2.5/arch/i386/kernel/time.c timer-2.5/arch/i386/kernel/time.c
@@ -268,8 +268,6 @@
 #endif
 }
 
-static int use_tsc;
-
 /*
  * This is the same as the above, except we _also_ save the current
  * Time Stamp Counter value at the time of the timer interrupt, so that

@@ -277,8 +275,6 @@
  */
 void timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
 {
-	int count;
-
 	/*
 	 * Here we are in the timer irq handler. We just have irqs locally
 	 * disabled but we don't know if the timer_bh is running on the other

diff -Naur -X ../dontdiff timer2-2.5/arch/i386/kernel/timers/timer.c timer-2.5/arch/i386/kernel/timers/timer.c
@@ -2,31 +2,34 @@
 #include <asm/timer.h>
 
 /* list of externed timers */
-#ifndef CONFIG_X86_TSC
 extern struct timer_opts timer_pit;
-#endif
 extern struct timer_opts timer_tsc;
 
-/* list of timers, ordered by preference */
-struct timer_opts* timers[] = {
-	&timer_tsc
+/* list of timers, ordered by preference, NULL terminated */
+static struct timer_opts* timers[] = {
+	&timer_tsc,
 #ifndef CONFIG_X86_TSC
-	,&timer_pit
+	&timer_pit,
 #endif
+	NULL,
 };
 
-#define NR_TIMERS (sizeof(timers)/sizeof(timers[0]))
 
 /* iterates through the list of timers, returning the first 
  * one that initializes successfully.
  */
 struct timer_opts* select_timer(void)
 {
-	int i;
+	int i = 0;
+	
 	/* find most preferred working timer */
-	for(i=0; i < NR_TIMERS; i++)
-		if(timers[i]->init())
-			return timers[i];
+	while (timers[i]) {
+		if (timers[i]->init)
+			if (timers[i]->init() == 0)
+				return timers[i];
+		++i;
+	}
+		
 	panic("select_timer: Cannot find a suitable timer\n");
-	return 0;
+	return NULL;
 }

diff -Naur -X ../dontdiff timer2-2.5/arch/i386/kernel/timers/timer_pit.c timer-2.5/arch/i386/kernel/timers/timer_pit.c
@@ -15,7 +15,7 @@
 
 static int init_pit(void)
 {
-	return 1;
+	return 0;
 }
 
 static void mark_offset_pit(void)

@@ -122,7 +122,7 @@
 
 /* tsc timer_opts struct */
 struct timer_opts timer_pit = {
-	init: init_pit, 
-	mark_offset: mark_offset_pit, 
-	get_offset: get_offset_pit
+	.init =		init_pit, 
+	.mark_offset =	mark_offset_pit, 
+	.get_offset =	get_offset_pit,
 };

diff -Naur -X ../dontdiff timer2-2.5/arch/i386/kernel/timers/timer_tsc.c timer-2.5/arch/i386/kernel/timers/timer_tsc.c
@@ -6,6 +6,7 @@
 #include <linux/spinlock.h>
 #include <linux/init.h>
 #include <linux/timex.h>
+#include <linux/errno.h>
 
 #include <asm/timer.h>
 #include <asm/io.h>

@@ -263,17 +264,17 @@
 #ifdef CONFIG_CPU_FREQ
 			cpufreq_register_notifier(&time_cpufreq_notifier_block, CPUFREQ_TRANSITION_NOTIFIER);
 #endif
-			return 1;
+			return 0;
 		}
 	}
-	return 0;
+	return -ENODEV;
 }
 
 /************************************************************/
 
 /* tsc timer_opts struct */
 struct timer_opts timer_tsc = {
-	init: init_tsc, 
-	mark_offset: mark_offset_tsc, 
-	get_offset: get_offset_tsc
+	.init =		init_tsc,
+	.mark_offset =	mark_offset_tsc, 
+	.get_offset =	get_offset_tsc,
 };

diff -Naur -X ../dontdiff timer2-2.5/include/asm-i386/timer.h timer-2.5/include/asm-i386/timer.h
@@ -1,14 +1,22 @@
 #ifndef _ASMi386_TIMER_H
 #define _ASMi386_TIMER_H
 
+/**
+ * struct timer_ops - used to define a timer source
+ *
+ * @init: Probes and initializes the timer.  Returns 0 on success, anything
+ *	else on failure.
+ * @mark_offset: called by the timer interrupt
+ * @get_offset: called by gettimeofday().  Returns the number of ms since the
+ *	last timer intruupt.
+ */
 struct timer_opts{
-	/* probes and initializes timer. returns 1 on sucess, 0 on failure */
 	int (*init)(void);
-	/* called by the timer interrupt */
 	void (*mark_offset)(void);
-	/* called by gettimeofday. returns # ms since the last timer interrupt */
 	unsigned long (*get_offset)(void);
 };
+
 #define TICK_SIZE (tick_nsec / 1000)
-struct timer_opts* select_timer(void);
+
+extern struct timer_opts* select_timer(void);
 #endif

Argh, wrong repo, try this:

	bk://linuxusb.bkbits.net/timer-2.5

Sorry about that.

greg k-h
(drowning in different bk trees...)