clocksource: convert x86 to generic i8253 clocksource

Convert x86 i8253 clocksource code to use generic i8253 clocksource. Acked-by: John Stultz <john.stultz@linaro.org> Acked-by: Thomas Gleixner <tglx@linutronix.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@redhat.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

clocksource: convert x86 to generic i8253 clocksource
Convert x86 i8253 clocksource code to use generic i8253 clocksource. Acked-by: John Stultz <john.stultz@linaro.org> Acked-by: Thomas Gleixner <tglx@linutronix.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@redhat.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Russell King
1 parent 8c414ff3f4
Showing 3 changed files with 4 additions and 78 deletions Side-by-side Diff
arch/x86/Kconfig
arch/x86/include/asm/i8253.h
arch/x86/kernel/i8253.c
@@ -8,6 +8,7 @@
  
 config X86_32
 	def_bool !64BIT
+	select CLKSRC_I8253
  
 config X86_64
 	def_bool 64BIT
@@ -6,6 +6,8 @@
 #define PIT_CH0			0x40
 #define PIT_CH2			0x42
  
+#define PIT_LATCH	LATCH
+
 extern raw_spinlock_t i8253_lock;
  
 extern struct clock_event_device *global_clock_event;
@@ -117,81 +117,6 @@
 }
  
 #ifndef CONFIG_X86_64
-/*
- * Since the PIT overflows every tick, its not very useful
- * to just read by itself. So use jiffies to emulate a free
- * running counter:
- */
-static cycle_t pit_read(struct clocksource *cs)
-{
-	static int old_count;
-	static u32 old_jifs;
-	unsigned long flags;
-	int count;
-	u32 jifs;
-
-	raw_spin_lock_irqsave(&i8253_lock, flags);
-	/*
-	 * Although our caller may have the read side of xtime_lock,
-	 * this is now a seqlock, and we are cheating in this routine
-	 * by having side effects on state that we cannot undo if
-	 * there is a collision on the seqlock and our caller has to
-	 * retry.  (Namely, old_jifs and old_count.)  So we must treat
-	 * jiffies as volatile despite the lock.  We read jiffies
-	 * before latching the timer count to guarantee that although
-	 * the jiffies value might be older than the count (that is,
-	 * the counter may underflow between the last point where
-	 * jiffies was incremented and the point where we latch the
-	 * count), it cannot be newer.
-	 */
-	jifs = jiffies;
-	outb_pit(0x00, PIT_MODE);	/* latch the count ASAP */
-	count = inb_pit(PIT_CH0);	/* read the latched count */
-	count |= inb_pit(PIT_CH0) << 8;
-
-	/* VIA686a test code... reset the latch if count > max + 1 */
-	if (count > LATCH) {
-		outb_pit(0x34, PIT_MODE);
-		outb_pit(LATCH & 0xff, PIT_CH0);
-		outb_pit(LATCH >> 8, PIT_CH0);
-		count = LATCH - 1;
-	}
-
-	/*
-	 * It's possible for count to appear to go the wrong way for a
-	 * couple of reasons:
-	 *
-	 *  1. The timer counter underflows, but we haven't handled the
-	 *     resulting interrupt and incremented jiffies yet.
-	 *  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.)
-	 *
-	 * Previous attempts to handle these cases intelligently were
-	 * buggy, so we just do the simple thing now.
-	 */
-	if (count > old_count && jifs == old_jifs)
-		count = old_count;
-
-	old_count = count;
-	old_jifs = jifs;
-
-	raw_spin_unlock_irqrestore(&i8253_lock, flags);
-
-	count = (LATCH - 1) - count;
-
-	return (cycle_t)(jifs * LATCH) + count;
-}
-
-static struct clocksource pit_cs = {
-	.name		= "pit",
-	.rating		= 110,
-	.read		= pit_read,
-	.mask		= CLOCKSOURCE_MASK(32),
-	.mult		= 0,
-	.shift		= 20,
-};
-
 static int __init init_pit_clocksource(void)
 {
 	 /*
@@ -205,9 +130,7 @@
 	    pit_ce.mode != CLOCK_EVT_MODE_PERIODIC)
 		return 0;
  
-	pit_cs.mult = clocksource_hz2mult(CLOCK_TICK_RATE, pit_cs.shift);
-
-	return clocksource_register(&pit_cs);
+	return clocksource_i8253_init();
 }
 arch_initcall(init_pit_clocksource);
...	...	@@ -8,6 +8,7 @@
8	8
9	9	config X86_32
10	10	def_bool !64BIT
	11	+ select CLKSRC_I8253
11	12
12	13	config X86_64
13	14	def_bool 64BIT
...	...	@@ -6,6 +6,8 @@
6	6	#define PIT_CH0 0x40
7	7	#define PIT_CH2 0x42
8	8
	9	+#define PIT_LATCH LATCH
	10	+
9	11	extern raw_spinlock_t i8253_lock;
10	12
11	13	extern struct clock_event_device *global_clock_event;
...	...	@@ -117,81 +117,6 @@
117	117	}
118	118
119	119	#ifndef CONFIG_X86_64
120		-/*
121		- * Since the PIT overflows every tick, its not very useful
122		- * to just read by itself. So use jiffies to emulate a free
123		- * running counter:
124		- */
125		-static cycle_t pit_read(struct clocksource *cs)
126		-{
127		- static int old_count;
128		- static u32 old_jifs;
129		- unsigned long flags;
130		- int count;
131		- u32 jifs;
132		-
133		- raw_spin_lock_irqsave(&i8253_lock, flags);
134		- /*
135		- * Although our caller may have the read side of xtime_lock,
136		- * this is now a seqlock, and we are cheating in this routine
137		- * by having side effects on state that we cannot undo if
138		- * there is a collision on the seqlock and our caller has to
139		- * retry. (Namely, old_jifs and old_count.) So we must treat
140		- * jiffies as volatile despite the lock. We read jiffies
141		- * before latching the timer count to guarantee that although
142		- * the jiffies value might be older than the count (that is,
143		- * the counter may underflow between the last point where
144		- * jiffies was incremented and the point where we latch the
145		- * count), it cannot be newer.
146		- */
147		- jifs = jiffies;
148		- outb_pit(0x00, PIT_MODE); /* latch the count ASAP */
149		- count = inb_pit(PIT_CH0); /* read the latched count */
150		- count \|= inb_pit(PIT_CH0) << 8;
151		-
152		- /* VIA686a test code... reset the latch if count > max + 1 */
153		- if (count > LATCH) {
154		- outb_pit(0x34, PIT_MODE);
155		- outb_pit(LATCH & 0xff, PIT_CH0);
156		- outb_pit(LATCH >> 8, PIT_CH0);
157		- count = LATCH - 1;
158		- }
159		-
160		- /*
161		- * It's possible for count to appear to go the wrong way for a
162		- * couple of reasons:
163		- *
164		- * 1. The timer counter underflows, but we haven't handled the
165		- * resulting interrupt and incremented jiffies yet.
166		- * 2. Hardware problem with the timer, not giving us continuous time,
167		- * the counter does small "jumps" upwards on some Pentium systems,
168		- * (see c't 95/10 page 335 for Neptun bug.)
169		- *
170		- * Previous attempts to handle these cases intelligently were
171		- * buggy, so we just do the simple thing now.
172		- */
173		- if (count > old_count && jifs == old_jifs)
174		- count = old_count;
175		-
176		- old_count = count;
177		- old_jifs = jifs;
178		-
179		- raw_spin_unlock_irqrestore(&i8253_lock, flags);
180		-
181		- count = (LATCH - 1) - count;
182		-
183		- return (cycle_t)(jifs * LATCH) + count;
184		-}
185		-
186		-static struct clocksource pit_cs = {
187		- .name = "pit",
188		- .rating = 110,
189		- .read = pit_read,
190		- .mask = CLOCKSOURCE_MASK(32),
191		- .mult = 0,
192		- .shift = 20,
193		-};
194		-
195	120	static int __init init_pit_clocksource(void)
196	121	{
197	122	/*
...	...	@@ -205,9 +130,7 @@
205	130	pit_ce.mode != CLOCK_EVT_MODE_PERIODIC)
206	131	return 0;
207	132
208		- pit_cs.mult = clocksource_hz2mult(CLOCK_TICK_RATE, pit_cs.shift);
209		-
210		- return clocksource_register(&pit_cs);
	133	+ return clocksource_i8253_init();
211	134	}
212	135	arch_initcall(init_pit_clocksource);
213	136