Re: [Geekos-devel] timer munging

[David H. <da...@cs...>]

I tried your patch, and it seems to work fine, although the messages
print out more than once per second.

I like the idea of being able to specify the rate of the timer
interrupts.  Maybe you could explain how this works in more detail?

-Dave


On Fri, Jan 11, 2002 at 11:15:02PM -0600, Parc wrote:
> I've munged together a couple lines to set the timer to 10ms jiffies,
> and added a sleep().  Could somebody try these out for me?  For some
> reason I don't get the correct timing occasionally.  This patch should
> cause the kernel to loop saying "tick" once a second.
> 
> Thanks
> 
> Index: drivers/timer.c
> ===================================================================
> RCS file: /cvsroot/geekos/drivers/timer.c,v
> retrieving revision 1.2
> diff -c -r1.2 timer.c
> *** drivers/timer.c	2001/12/24 15:35:57	1.2
> --- drivers/timer.c	2002/01/12 05:10:29
> ***************
> *** 11,16 ****
> --- 11,20 ----
>   #include "sys/geekos/kthread.h"
>   #include "sys/geekos/timer.h"
>   
> + #define TICKRATE	1193182
> + //#define FIND_RATE(hz) (((TICKRATE + hz) / 2) / hz)
> + #define FIND_RATE(hz) (((TICKRATE + hz) / 2) / hz)
> + 
>   // global tick counter
>   volatile unsigned long g_numTicks;
>   
> ***************
> *** 56,61 ****
> --- 60,72 ----
>   
>       Print( "Initializing timer...\n" );
>   
> +     //Set the tick rate to 10ms
> +     disable_interrupts();
> +     out_byte(0x043, 0x34);
> +     out_byte(0x040, FIND_RATE(100) & 0xff);
> +     out_byte(0x040, FIND_RATE(100) >> 8);
> +     enable_interrupts();
> + 
>       // Install an interrupt handler for the timer IRQ
>       install_irq( TIMER_IRQ, &timer_interrupt_handler );
>   
> ***************
> *** 63,66 ****
> --- 74,83 ----
>       irqMask = get_irq_mask();
>       irqMask &= ~(1 << TIMER_IRQ);
>       set_irq_mask( irqMask );
> + }
> + 
> + void sleep(int time) {
> +    long start = g_numTicks + time +1; 
> +    Print("Sleeping from %x to %x\n",g_numTicks,start);
> +    while((g_numTicks - start) > 0) ; //spin
>   }
> Index: include/sys/geekos/timer.h
> ===================================================================
> RCS file: /cvsroot/geekos/include/sys/geekos/timer.h,v
> retrieving revision 1.2
> diff -c -r1.2 timer.h
> *** include/sys/geekos/timer.h	2001/12/24 15:35:57	1.2
> --- include/sys/geekos/timer.h	2002/01/12 05:10:29
> ***************
> *** 13,17 ****
> --- 13,18 ----
>   extern volatile unsigned long g_numTicks;
>   
>   void init_timer( void );
> + void sleep( int time );
>   
>   #endif // TIMER_H
> Index: kern/main.c
> ===================================================================
> RCS file: /cvsroot/geekos/kern/main.c,v
> retrieving revision 1.6
> diff -c -r1.6 main.c
> *** kern/main.c	2001/12/24 15:35:57	1.6
> --- kern/main.c	2002/01/12 05:10:30
> ***************
> *** 51,56 ****
> --- 53,62 ----
>       // Test Join() function
>       {
>   	struct kernel_thread* child;
> +         for(; ;) {
> +             sleep(100);
> +             Print("tick.\n");
> +         }
>   	Print( "Starting child...\n" );
>   	child = start_kernel_thread( &test_join, 0, PRIORITY_NORMAL, FALSE );
>   	Join( child );