[PATCH] linux-2.5.54_delay-cleanup_A0

[PATCH] linux-2.5.54_delay-cleanup_A0

[john stultz]

Linus, all, 
	I've been busy with other things, so I've just been sitting on this for
a while. Anyway, I figured it was about time to resend. 

This patch tries to cleanup the delay code by moving the timer-specific
implementations into the timer_ops struct. Thus, rather then doing:

	if(x86_delay_tsc)
		__rdtsc_delay(loops);
	else if(x86_delay_cyclone)
		__cyclone_delay(loops);
	else if(whatever....

we just simply do:

	if(timer)
		timer->delay(loops);


Making it much easier to accommodate alternate time sources. 

Please apply.

thanks
-john
 
diff -Nru a/arch/i386/kernel/timers/timer_cyclone.c b/arch/i386/kernel/timers/timer_cyclone.c
--- a/arch/i386/kernel/timers/timer_cyclone.c	Tue Jan  7 17:11:03 2003
+++ b/arch/i386/kernel/timers/timer_cyclone.c	Tue Jan  7 17:11:03 2003
@@ -150,7 +150,6 @@
 }
 
 
-#if 0 /* XXX future work */
 static void delay_cyclone(unsigned long loops)
 {
 	unsigned long bclock, now;
@@ -162,12 +161,12 @@
 		now = cyclone_timer[0];
 	} while ((now-bclock) < loops);
 }
-#endif
 /************************************************************/
 
 /* cyclone timer_opts struct */
 struct timer_opts timer_cyclone = {
 	.init = init_cyclone, 
 	.mark_offset = mark_offset_cyclone, 
-	.get_offset = get_offset_cyclone
+	.get_offset = get_offset_cyclone,
+	.delay = delay_cyclone,
 };
diff -Nru a/arch/i386/kernel/timers/timer_pit.c b/arch/i386/kernel/timers/timer_pit.c
--- a/arch/i386/kernel/timers/timer_pit.c	Tue Jan  7 17:11:03 2003
+++ b/arch/i386/kernel/timers/timer_pit.c	Tue Jan  7 17:11:03 2003
@@ -27,6 +27,19 @@
 	/* nothing needed */
 }
 
+static void delay_pit(unsigned long loops)
+{
+	int d0;
+	__asm__ __volatile__(
+		"\tjmp 1f\n"
+		".align 16\n"
+		"1:\tjmp 2f\n"
+		".align 16\n"
+		"2:\tdecl %0\n\tjns 2b"
+		:"=&a" (d0)
+		:"0" (loops));
+}
+
 
 /* This function must be called with interrupts disabled 
  * It was inspired by Steve McCanne's microtime-i386 for BSD.  -- jrs
@@ -129,4 +142,5 @@
 	.init =		init_pit, 
 	.mark_offset =	mark_offset_pit, 
 	.get_offset =	get_offset_pit,
+	.delay = delay_pit,
 };
diff -Nru a/arch/i386/kernel/timers/timer_tsc.c b/arch/i386/kernel/timers/timer_tsc.c
--- a/arch/i386/kernel/timers/timer_tsc.c	Tue Jan  7 17:11:03 2003
+++ b/arch/i386/kernel/timers/timer_tsc.c	Tue Jan  7 17:11:03 2003
@@ -16,7 +16,6 @@
 
 int tsc_disable __initdata = 0;
 
-extern int x86_udelay_tsc;
 extern spinlock_t i8253_lock;
 
 static int use_tsc;
@@ -107,6 +106,17 @@
 	delay_at_last_interrupt = (count + LATCH/2) / LATCH;
 }
 
+static void delay_tsc(unsigned long loops)
+{
+	unsigned long bclock, now;
+	
+	rdtscl(bclock);
+	do
+	{
+		rep_nop();
+		rdtscl(now);
+	} while ((now-bclock) < loops);
+}
 
 /* ------ Calibrate the TSC ------- 
  * Return 2^32 * (1 / (TSC clocks per usec)) for do_fast_gettimeoffset().
@@ -272,8 +282,6 @@
 			 *	We could be more selective here I suspect
 			 *	and just enable this for the next intel chips ?
 			 */
-			x86_udelay_tsc = 1;
-
 			/* 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.
@@ -310,4 +318,5 @@
 	.init =		init_tsc,
 	.mark_offset =	mark_offset_tsc, 
 	.get_offset =	get_offset_tsc,
+	.delay = delay_tsc,
 };
diff -Nru a/arch/i386/lib/delay.c b/arch/i386/lib/delay.c
--- a/arch/i386/lib/delay.c	Tue Jan  7 17:11:03 2003
+++ b/arch/i386/lib/delay.c	Tue Jan  7 17:11:03 2003
@@ -15,35 +15,18 @@
 #include <linux/delay.h>
 #include <asm/processor.h>
 #include <asm/delay.h>
+#include <asm/timer.h>
 
 #ifdef CONFIG_SMP
 #include <asm/smp.h>
 #endif
 
-int x86_udelay_tsc = 0;		/* Delay via TSC */
+extern struct timer_opts* timer;
 
-	
 /*
- *	Do a udelay using the TSC for any CPU that happens
- *	to have one that we trust.
+ *	Backup non-TSC based delay loop.
+ *	Used until a timer is chosen.
  */
-
-static void __rdtsc_delay(unsigned long loops)
-{
-	unsigned long bclock, now;
-	
-	rdtscl(bclock);
-	do
-	{
-		rep_nop();
-		rdtscl(now);
-	} while ((now-bclock) < loops);
-}
-
-/*
- *	Non TSC based delay loop for 386, 486, MediaGX
- */
- 
 static void __loop_delay(unsigned long loops)
 {
 	int d0;
@@ -59,8 +42,8 @@
 
 void __delay(unsigned long loops)
 {
-	if (x86_udelay_tsc)
-		__rdtsc_delay(loops);
+	if(timer)
+		timer->delay(loops);
 	else
 		__loop_delay(loops);
 }
diff -Nru a/include/asm-i386/timer.h b/include/asm-i386/timer.h
--- a/include/asm-i386/timer.h	Tue Jan  7 17:11:03 2003
+++ b/include/asm-i386/timer.h	Tue Jan  7 17:11:03 2003
@@ -14,6 +14,7 @@
 	int (*init)(void);
 	void (*mark_offset)(void);
 	unsigned long (*get_offset)(void);
+	void (*delay)(unsigned long);
 };
 
 #define TICK_SIZE (tick_nsec / 1000)

Re: [PATCH] linux-2.5.54_delay-cleanup_A0

[Linus Torvalds]

On 7 Jan 2003, john stultz wrote:
> 
> 	if (timer)
> 		timer->delay(loops);

Why the "if (timer)"?

Wouldn't it be saner to initialize the timer to something that can at 
least do estimated loops, and then just unconditionally do

	timer->delay(..);

instead?

		Linus

Re: [PATCH] linux-2.5.54_delay-cleanup_A0

[john stultz]

On Tue, 2003-01-07 at 19:29, Linus Torvalds wrote:
> Wouldn't it be saner to initialize the timer to something that can at 
> least do estimated loops, and then just unconditionally do
> 
> 	timer->delay(..);
> 
> instead?

Basically a default timer_null structure? Sure that can be done (I think
others have suggested this as well, but I've just not had the time to
get around to it). I'll see if I can scratch that out quickly and
resend. 

thanks for the feedback!
-john

Re: [PATCH] linux-2.5.54_delay-cleanup_A0

[Pavel Machek]

Hi!

> Linus, all, 
> 	I've been busy with other things, so I've just been sitting on this for
> a while. Anyway, I figured it was about time to resend. 
> 
> This patch tries to cleanup the delay code by moving the timer-specific
> implementations into the timer_ops struct. Thus, rather then doing:
> 
> 	if(x86_delay_tsc)
> 		__rdtsc_delay(loops);
> 	else if(x86_delay_cyclone)
> 		__cyclone_delay(loops);
> 	else if(whatever....
> 
> we just simply do:
> 
> 	if(timer)
> 		timer->delay(loops);
> 
> diff -Nru a/arch/i386/kernel/timers/timer_pit.c b/arch/i386/kernel/timers/timer_pit.c
> --- a/arch/i386/kernel/timers/timer_pit.c	Tue Jan  7 17:11:03 2003
> +++ b/arch/i386/kernel/timers/timer_pit.c	Tue Jan  7 17:11:03 2003
> @@ -27,6 +27,19 @@
>  	/* nothing needed */
>  }
>  
> +static void delay_pit(unsigned long loops)
> +{
> +	int d0;
> +	__asm__ __volatile__(
> +		"\tjmp 1f\n"
> +		".align 16\n"
> +		"1:\tjmp 2f\n"
> +		".align 16\n"
> +		"2:\tdecl %0\n\tjns 2b"
> +		:"=&a" (d0)
> +		:"0" (loops));
> +}
> +

But... this is not using pit to do the delay, right? It is sensitive
to CPU clock changes, pit-delay should not be.

								Pavel

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