RE: [PATCH][2.6][2/5]Support for HPET based timer

["Pallipadi, Venkatesh" <venkatesh.pallipadi@intel.com>]

Fixmap is for HPET memory map address access. As the timer
initialization happen 
early in the boot sequence (before vm initialization), we need to have
fixmap() 
and fix_to_virt() to access HPET memory map address.

Yes. Most of the code is generic, and can run on other platforms. The
only reason 
I have that check is because, I haven't got chance to test this patch on
other 
platforms.

Thanks,
-Venkatesh 

> -----Original Message-----
> From: Vojtech Pavlik [mailto:vojtech@suse.cz] 
> Sent: Tuesday, August 19, 2003 3:39 PM
> To: Pallipadi, Venkatesh
> Cc: linux-kernel@vger.kernel.org; torvalds@osdl.org; 
> Nakajima, Jun; Mallick, Asit K
> Subject: Re: [PATCH][2.6][2/5]Support for HPET based timer
> 
> 
> On Tue, Aug 19, 2003 at 12:20:02PM -0700, Pallipadi, Venkatesh wrote:
> 
> > 2/5 - hpet2.patch - All the changes required to use HPET in place
> >                     of PIT as the kernel base-timer at IRQ 0.
> 
> What are you using the fixmap() for? i386 doesn't have vsyscalls ...
> 
> Why are you limiting the HPET vendor ID to Intel? This code will
> happily run on other vendor hardware as well ...
> 
>  
> > diff -purN linux-2.6.0-test1/arch/i386/kernel/apic.c 
> linux-2.6.0-test1-hpet/arch/i386/kernel/apic.c
> > --- linux-2.6.0-test1/arch/i386/kernel/apic.c	
> 2003-07-13 20:39:27.000000000 -0700
> > +++ linux-2.6.0-test1-hpet/arch/i386/kernel/apic.c	
> 2003-08-13 11:36:24.000000000 -0700
> > @@ -34,6 +34,7 @@
> >  #include <asm/pgalloc.h>
> >  #include <asm/desc.h>
> >  #include <asm/arch_hooks.h>
> > +#include <asm/hpet.h>
> >  
> >  #include <mach_apic.h>
> >  
> > @@ -749,7 +750,8 @@ static unsigned int __init get_8254_time
> >  	return count;
> >  }
> >  
> > -void __init wait_8254_wraparound(void)
> > +/* next tick in 8254 can be caught by catching timer wraparound */
> > +static void __init wait_8254_wraparound(void)
> >  {
> >  	unsigned int curr_count, prev_count=~0;
> >  	int delta;
> > @@ -771,6 +773,12 @@ void __init wait_8254_wraparound(void)
> >  }
> >  
> >  /*
> > + * Default initialization for 8254 timers. If we use other 
> timers like HPET,
> > + * we override this later 
> > + */
> > +void (*wait_timer_tick)(void) = wait_8254_wraparound;
> > +
> > +/*
> >   * This function sets up the local APIC timer, with a timeout of
> >   * 'clocks' APIC bus clock. During calibration we actually call
> >   * this function twice on the boot CPU, once with a bogus timeout
> > @@ -811,7 +819,7 @@ static void setup_APIC_timer(unsigned in
> >  	/*
> >  	 * Wait for IRQ0's slice:
> >  	 */
> > -	wait_8254_wraparound();
> > +	wait_timer_tick();
> >  
> >  	__setup_APIC_LVTT(clocks);
> >  
> > @@ -854,7 +862,7 @@ int __init calibrate_APIC_clock(void)
> >  	 * (the current tick might have been already half done)
> >  	 */
> >  
> > -	wait_8254_wraparound();
> > +	wait_timer_tick();
> >  
> >  	/*
> >  	 * We wrapped around just now. Let's start:
> > @@ -867,7 +875,7 @@ int __init calibrate_APIC_clock(void)
> >  	 * Let's wait LOOPS wraprounds:
> >  	 */
> >  	for (i = 0; i < LOOPS; i++)
> > -		wait_8254_wraparound();
> > +		wait_timer_tick();
> >  
> >  	tt2 = apic_read(APIC_TMCCT);
> >  	if (cpu_has_tsc)
> > diff -purN linux-2.6.0-test1/arch/i386/kernel/time.c 
> linux-2.6.0-test1-hpet/arch/i386/kernel/time.c
> > --- linux-2.6.0-test1/arch/i386/kernel/time.c	
> 2003-07-13 20:34:29.000000000 -0700
> > +++ linux-2.6.0-test1-hpet/arch/i386/kernel/time.c	
> 2003-08-18 12:36:25.000000000 -0700
> > @@ -60,6 +60,8 @@
> >  #include <linux/timex.h>
> >  #include <linux/config.h>
> >  
> > +#include <asm/hpet.h>
> > +
> >  #include <asm/arch_hooks.h>
> >  
> >  #include "io_ports.h"
> > @@ -298,6 +300,12 @@ void __init time_init(void)
> >  	xtime.tv_nsec = (INITIAL_JIFFIES % HZ) * (NSEC_PER_SEC / HZ);
> >  	wall_to_monotonic.tv_nsec = -xtime.tv_nsec;
> >  
> > +#ifdef CONFIG_HPET_TIMER
> > +	if (hpet_enable() >= 0) {
> > +		printk("Using HPET for base-timer\n");
> > +	}
> > +#endif
> > +
> >  	cur_timer = select_timer();
> >  	time_init_hook();
> >  }
> > diff -purN linux-2.6.0-test1/arch/i386/kernel/time_hpet.c 
> linux-2.6.0-test1-hpet/arch/i386/kernel/time_hpet.c
> > --- linux-2.6.0-test1/arch/i386/kernel/time_hpet.c	
> 1969-12-31 16:00:00.000000000 -0800
> > +++ linux-2.6.0-test1-hpet/arch/i386/kernel/time_hpet.c	
> 2003-08-18 20:22:06.000000000 -0700
> > @@ -0,0 +1,153 @@
> > +/*
> > + *  linux/arch/i386/kernel/time_hpet.c
> > + *  This code largely copied from arch/x86_64/kernel/time.c
> > + *  See that file for credits.
> > + *
> > + *  2003-06-30    Venkatesh Pallipadi - Additional changes 
> for HPET support
> > + */
> > +
> > +#include <linux/errno.h>
> > +#include <linux/kernel.h>
> > +#include <linux/param.h>
> > +#include <linux/string.h>
> > +#include <linux/init.h>
> > +#include <linux/smp.h>
> > +
> > +#include <asm/timer.h>
> > +#include <asm/fixmap.h>
> > +#include <asm/apic.h>
> > +
> > +#include <linux/timex.h>
> > +#include <linux/config.h>
> > +
> > +#include <asm/hpet.h>
> > +
> > +unsigned long hpet_period;	/* fsecs / HPET clock */
> > +unsigned long hpet_tick;	/* hpet clks count per tick */
> > +unsigned long hpet_address;	/* hpet memory map address */
> > +
> > +static int use_hpet; 		/* can be used for 
> runtime check of hpet */
> > +static int boot_hpet_disable; 	/* boottime override 
> for HPET timer */
> > +
> > +#define FSEC_TO_USEC (1000000000UL)
> > +
> > +#ifdef CONFIG_X86_LOCAL_APIC
> > +/*
> > + * HPET counters dont wrap around on every tick. They just 
> change the 
> > + * comparator value and continue. Next tick can be caught 
> by checking 
> > + * for a change in the comparator value. Used in apic.c.
> > + */
> > +void __init wait_hpet_tick(void)
> > +{
> > +	unsigned int start_cmp_val, end_cmp_val;
> > +
> > +	start_cmp_val = hpet_readl(HPET_T0_CMP);
> > +	do {
> > +		end_cmp_val = hpet_readl(HPET_T0_CMP);
> > +	} while (start_cmp_val == end_cmp_val);
> > +}
> > +#endif
> > +
> > +/*
> > + * Check whether HPET was found by ACPI boot parse. If yes 
> setup HPET 
> > + * counter 0 for kernel base timer. 
> > + */
> > +int __init hpet_enable(void)
> > +{
> > +	unsigned int cfg, id;
> > +	unsigned long tick_fsec_low, tick_fsec_high; /* tick in 
> femto sec */
> > +	unsigned long hpet_tick_rem;
> > +
> > +	if (boot_hpet_disable)
> > +		return -1;
> > +
> > +	if (!hpet_address) {
> > +		return -1;
> > +	}
> > +	set_fixmap_nocache(FIX_HPET_BASE, hpet_address);
> > +	printk(KERN_INFO "HPET enabled at %#lx\n", hpet_address);
> > +
> > +	/*
> > +	 * Read the period, compute tick and quotient.
> > +	 */
> > +	id = hpet_readl(HPET_ID);
> > +
> > +	/*
> > +	 * We are checking for value '1' or more in number field. 
> > +	 * So, we are OK with HPET_EMULATE_RTC part too, where we need
> > +	 * to have atleast 2 timers.
> > +	 */
> > +	if (!(id & HPET_ID_NUMBER) ||
> > +	    !(id & HPET_ID_LEGSUP))
> > +		return -1;
> > +
> > +	if (((id & HPET_ID_VENDOR) >> HPET_ID_VENDOR_SHIFT) != 
> > +				HPET_ID_VENDOR_8086)
> > +		return -1;
> > +
> > +	hpet_period = hpet_readl(HPET_PERIOD);
> > +	if ((hpet_period < HPET_MIN_PERIOD) || (hpet_period > 
> HPET_MAX_PERIOD))
> > +		return -1;
> > +
> > +	/*
> > +	 * 64 bit math
> > +	 * First changing tick into fsec
> > +	 * Then 64 bit div to find number of hpet clk per tick
> > +	 */
> > +	ASM_MUL64_REG(tick_fsec_low, tick_fsec_high, 
> > +			KERNEL_TICK_USEC, FSEC_TO_USEC);
> > +	ASM_DIV64_REG(hpet_tick, hpet_tick_rem, 
> > +			hpet_period, tick_fsec_low, tick_fsec_high);
> > +
> > +	if (hpet_tick_rem > (hpet_period >> 1))
> > +		hpet_tick++; /* rounding the result */
> > +
> > +	/*
> > +	 * Stop the timers and reset the main counter.
> > +	 */
> > +	cfg = hpet_readl(HPET_CFG);
> > +	cfg &= ~HPET_CFG_ENABLE;
> > +	hpet_writel(cfg, HPET_CFG);
> > +	hpet_writel(0, HPET_COUNTER);
> > +	hpet_writel(0, HPET_COUNTER + 4);
> > +
> > +	/*
> > +	 * Set up timer 0, as periodic with first interrupt to 
> happen at 
> > +	 * hpet_tick, and period also hpet_tick.
> > +	 */
> > +	cfg = hpet_readl(HPET_T0_CFG);
> > +	cfg |= HPET_TN_ENABLE | HPET_TN_PERIODIC | 
> > +	       HPET_TN_SETVAL | HPET_TN_32BIT;
> > +	hpet_writel(cfg, HPET_T0_CFG);
> > +	hpet_writel(hpet_tick, HPET_T0_CMP);
> > +
> > +	/*
> > + 	 * Go!
> > + 	 */
> > +	cfg = hpet_readl(HPET_CFG);
> > +	cfg |= HPET_CFG_ENABLE | HPET_CFG_LEGACY;
> > +	hpet_writel(cfg, HPET_CFG);
> > +
> > +	use_hpet = 1;
> > +#ifdef CONFIG_X86_LOCAL_APIC
> > +	wait_timer_tick = wait_hpet_tick;
> > +#endif
> > +	return 0;
> > +}
> > +
> > +int is_hpet_enabled(void)
> > +{
> > +	return use_hpet;
> > +}
> > +
> > +static int __init hpet_setup(char* str)
> > +{
> > +	if (str) {
> > +		if (!strncmp("disable", str, 7))
> > +			boot_hpet_disable = 1;
> > +	}
> > +	return 1;
> > +}
> > +
> > +__setup("hpet=", hpet_setup);
> > +
> > diff -purN linux-2.6.0-test1/include/asm-i386/apic.h 
> linux-2.6.0-test1-hpet/include/asm-i386/apic.h
> > --- linux-2.6.0-test1/include/asm-i386/apic.h	
> 2003-07-13 20:38:53.000000000 -0700
> > +++ linux-2.6.0-test1-hpet/include/asm-i386/apic.h	
> 2003-08-13 11:34:37.000000000 -0700
> > @@ -64,6 +64,8 @@ static inline void ack_APIC_irq(void)
> >  	apic_write_around(APIC_EOI, 0);
> >  }
> >  
> > +extern void (*wait_timer_tick)(void);
> > +
> >  extern int get_maxlvt(void);
> >  extern void clear_local_APIC(void);
> >  extern void connect_bsp_APIC (void);
> > diff -purN linux-2.6.0-test1/include/asm-i386/fixmap.h 
> linux-2.6.0-test1-hpet/include/asm-i386/fixmap.h
> > --- linux-2.6.0-test1/include/asm-i386/fixmap.h	
> 2003-07-13 20:29:30.000000000 -0700
> > +++ linux-2.6.0-test1-hpet/include/asm-i386/fixmap.h	
> 2003-08-14 13:10:31.000000000 -0700
> > @@ -44,6 +44,9 @@
> >  enum fixed_addresses {
> >  	FIX_HOLE,
> >  	FIX_VSYSCALL,
> > +#ifdef CONFIG_HPET_TIMER
> > +	FIX_HPET_BASE,
> > +#endif
> >  #ifdef CONFIG_X86_LOCAL_APIC
> >  	FIX_APIC_BASE,	/* local (CPU) APIC) -- required for 
> SMP or not */
> >  #endif
> > diff -purN linux-2.6.0-test1/include/asm-i386/hpet.h 
> linux-2.6.0-test1-hpet/include/asm-i386/hpet.h
> > --- linux-2.6.0-test1/include/asm-i386/hpet.h	
> 1969-12-31 16:00:00.000000000 -0800
> > +++ linux-2.6.0-test1-hpet/include/asm-i386/hpet.h	
> 2003-08-18 20:22:40.000000000 -0700
> > @@ -0,0 +1,104 @@
> > +
> > +#ifndef _I386_HPET_H
> > +#define _I386_HPET_H
> > +
> > +#ifdef CONFIG_HPET_TIMER
> > +
> > +#include <linux/errno.h>
> > +#include <linux/module.h>
> > +#include <linux/sched.h>
> > +#include <linux/kernel.h>
> > +#include <linux/param.h>
> > +#include <linux/string.h>
> > +#include <linux/mm.h>
> > +#include <linux/interrupt.h>
> > +#include <linux/time.h>
> > +#include <linux/delay.h>
> > +#include <linux/init.h>
> > +#include <linux/smp.h>
> > +
> > +#include <asm/io.h>
> > +#include <asm/smp.h>
> > +#include <asm/irq.h>
> > +#include <asm/msr.h>
> > +#include <asm/delay.h>
> > +#include <asm/mpspec.h>
> > +#include <asm/uaccess.h>
> > +#include <asm/processor.h>
> > +
> > +#include <linux/timex.h>
> > +#include <linux/config.h>
> > +
> > +#include <asm/fixmap.h>
> > +
> > +/*
> > + * Documentation on HPET can be found at:
> > + *      http://www.intel.com/ial/home/sp/pcmmspec.htm
> > + *      ftp://download.intel.com/ial/home/sp/mmts098.pdf
> > + */
> > +
> > +#define HPET_ID		0x000
> > +#define HPET_PERIOD	0x004
> > +#define HPET_CFG	0x010
> > +#define HPET_STATUS	0x020
> > +#define HPET_COUNTER	0x0f0
> > +#define HPET_T0_CFG	0x100
> > +#define HPET_T0_CMP	0x108
> > +#define HPET_T0_ROUTE	0x110
> > +#define HPET_T1_CFG	0x120
> > +#define HPET_T1_CMP	0x128
> > +#define HPET_T1_ROUTE	0x130
> > +#define HPET_T2_CFG	0x140
> > +#define HPET_T2_CMP	0x148
> > +#define HPET_T2_ROUTE	0x150
> > +
> > +#define HPET_ID_VENDOR	0xffff0000
> > +#define HPET_ID_LEGSUP	0x00008000
> > +#define HPET_ID_NUMBER	0x00001f00
> > +#define HPET_ID_REV	0x000000ff
> > +
> > +#define HPET_ID_VENDOR_SHIFT	16
> > +#define HPET_ID_VENDOR_8086	0x8086
> > +
> > +#define HPET_CFG_ENABLE	0x001
> > +#define HPET_CFG_LEGACY	0x002
> > +
> > +#define HPET_TN_ENABLE		0x004
> > +#define HPET_TN_PERIODIC	0x008
> > +#define HPET_TN_PERIODIC_CAP	0x010
> > +#define HPET_TN_SETVAL		0x040
> > +#define HPET_TN_32BIT		0x100
> > +
> > +/* Use our own asm for 64 bit multiply/divide */
> > +#define ASM_MUL64_REG(eax_out,edx_out,reg_in,eax_in) 	
> 		\
> > +		__asm__ __volatile__("mull %2" 			
> 	\
> > +				:"=a" (eax_out), "=d" (edx_out) 
> 	\
> > +				:"r" (reg_in), "0" (eax_in))
> > +
> > +#define 
> ASM_DIV64_REG(eax_out,edx_out,reg_in,eax_in,edx_in) 		\
> > +		__asm__ __volatile__("divl %2" 			
> 	\
> > +				:"=a" (eax_out), "=d" (edx_out) 
> 	\
> > +				:"r" (reg_in), "0" (eax_in), 
> "1" (edx_in))
> > +
> > +#define hpet_readl(a)		
> readl(fix_to_virt(FIX_HPET_BASE) + a)
> > +#define hpet_writel(d,a)	writel(d, 
> fix_to_virt(FIX_HPET_BASE) + a)
> > +
> > +#define KERNEL_TICK_USEC 	(1000000UL/HZ)	/* tick value 
> in microsec */
> > +/* Max HPET Period is 10^8 femto sec as in HPET spec */
> > +#define HPET_MAX_PERIOD (100000000UL)
> > +/*
> > + * Min HPET period is 10^5 femto sec just for safety. If 
> it is less than this, 
> > + * then 32 bit HPET counter wrapsaround in less than 0.5 sec. 
> > + */
> > +#define HPET_MIN_PERIOD (100000UL)
> > +
> > +extern unsigned long hpet_period;	/* fsecs / HPET clock */
> > +extern unsigned long hpet_tick;  	/* hpet clks count per tick */
> > +extern unsigned long hpet_address;	/* hpet memory map address */
> > +extern unsigned long hpet_virt_address;	/* hpet kernel 
> virtual address */
> > +
> > +extern int hpet_enable(void);
> > +extern int is_hpet_enabled(void);
> > +
> > +#endif /* CONFIG_HPET_TIMER */
> > +#endif /* _I386_HPET_H */
> > diff -purN linux-2.6.0-test1/include/asm-i386/mc146818rtc.h 
> linux-2.6.0-test1-hpet/include/asm-i386/mc146818rtc.h
> > --- linux-2.6.0-test1/include/asm-i386/mc146818rtc.h	
> 2003-07-13 20:36:37.000000000 -0700
> > +++ linux-2.6.0-test1-hpet/include/asm-i386/mc146818rtc.h	
> 2003-08-18 20:23:43.000000000 -0700
> > @@ -24,6 +24,10 @@ outb_p((addr),RTC_PORT(0)); \
> >  outb_p((val),RTC_PORT(1)); \
> >  })
> >  
> > +#ifdef CONFIG_HPET_TIMER
> > +#define RTC_IRQ 0
> > +#else
> >  #define RTC_IRQ 8
> > +#endif
> >  
> >  #endif /* _ASM_MC146818RTC_H */
> > diff -purN 
> linux-2.6.0-test1/Documentation/kernel-parameters.txt 
> linux-2.6.0-test1-hpet/Documentation/kernel-parameters.txt
> > --- linux-2.6.0-test1/Documentation/kernel-parameters.txt   
>     2003-07-13 20:39:36.000000000 -0700
> > +++ 
> linux-2.6.0-test1-hpet/Documentation/kernel-parameters.txt  
> 2003-08-18 20:37:41.000000000 -0700
> > @@ -212,7 +212,10 @@ running once the system is up.
> > 			when calculating gettimeofday(). If 
> specicified timesource
> > 			is not avalible, it defaults to PIT. 
> > 			Format: { pit | tsc | cyclone | ... }
> > -
> > +
> > +	hpet=		[IA-32,HPET] option to disable HPET and use PIT.
> > +			Format: disable
> > +
> > 	cm206=		[HW,CD]
> > 			Format: { auto | [<io>,][<irq>] }
> >  
> > 
> > 
> 
> 
> 
> -- 
> Vojtech Pavlik
> SuSE Labs, SuSE CR
>