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

From: Pallipadi, Venkatesh
Date: Tue Aug 19 2003 - 19:21:02 EST

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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@xxxxxxx]
> Sent: Tuesday, August 19, 2003 3:39 PM
> To: Pallipadi, Venkatesh
> Cc: linux-kernel@xxxxxxxxxxxxxxx; torvalds@xxxxxxxx;
> 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
>
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