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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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08ec3c2d45
Make sched_clock() report time since boot rather than time since last timer interrupt. Make sched_clock() expand and scale the 32-bit TSC value running at IOCLK speed (~33MHz) to a 64-bit nanosecond counter, using cnt32_to_63() acquired from the ARM arch and without using slow DIVU instructions every call. Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
162 lines
4.2 KiB
C
162 lines
4.2 KiB
C
/* MN10300 Low level time management
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*
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* Copyright (C) 2007-2008 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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* - Derived from arch/i386/kernel/time.c
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public Licence
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* as published by the Free Software Foundation; either version
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* 2 of the Licence, or (at your option) any later version.
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*/
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#include <linux/sched.h>
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#include <linux/kernel.h>
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#include <linux/interrupt.h>
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#include <linux/time.h>
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#include <linux/init.h>
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#include <linux/smp.h>
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#include <linux/profile.h>
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#include <linux/cnt32_to_63.h>
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#include <asm/irq.h>
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#include <asm/div64.h>
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#include <asm/processor.h>
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#include <asm/intctl-regs.h>
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#include <asm/rtc.h>
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#ifdef CONFIG_MN10300_RTC
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unsigned long mn10300_ioclk; /* system I/O clock frequency */
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unsigned long mn10300_iobclk; /* system I/O clock frequency */
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unsigned long mn10300_tsc_per_HZ; /* number of ioclks per jiffy */
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#endif /* CONFIG_MN10300_RTC */
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static unsigned long mn10300_last_tsc; /* time-stamp counter at last time
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* interrupt occurred */
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static irqreturn_t timer_interrupt(int irq, void *dev_id);
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static struct irqaction timer_irq = {
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.handler = timer_interrupt,
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.flags = IRQF_DISABLED | IRQF_SHARED | IRQF_TIMER,
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.mask = CPU_MASK_NONE,
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.name = "timer",
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};
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static unsigned long sched_clock_multiplier;
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/*
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* scheduler clock - returns current time in nanosec units.
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*/
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unsigned long long sched_clock(void)
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{
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union {
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unsigned long long ll;
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unsigned l[2];
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} tsc64, result;
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unsigned long tsc, tmp;
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unsigned product[3]; /* 96-bit intermediate value */
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/* read the TSC value
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*/
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tsc = 0 - get_cycles(); /* get_cycles() counts down */
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/* expand to 64-bits.
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* - sched_clock() must be called once a minute or better or the
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* following will go horribly wrong - see cnt32_to_63()
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*/
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tsc64.ll = cnt32_to_63(tsc) & 0x7fffffffffffffffULL;
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/* scale the 64-bit TSC value to a nanosecond value via a 96-bit
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* intermediate
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*/
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asm("mulu %2,%0,%3,%0 \n" /* LSW * mult -> 0:%3:%0 */
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"mulu %2,%1,%2,%1 \n" /* MSW * mult -> %2:%1:0 */
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"add %3,%1 \n"
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"addc 0,%2 \n" /* result in %2:%1:%0 */
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: "=r"(product[0]), "=r"(product[1]), "=r"(product[2]), "=r"(tmp)
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: "0"(tsc64.l[0]), "1"(tsc64.l[1]), "2"(sched_clock_multiplier)
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: "cc");
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result.l[0] = product[1] << 16 | product[0] >> 16;
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result.l[1] = product[2] << 16 | product[1] >> 16;
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return result.ll;
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}
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/*
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* initialise the scheduler clock
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*/
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static void __init mn10300_sched_clock_init(void)
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{
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sched_clock_multiplier =
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__muldiv64u(NSEC_PER_SEC, 1 << 16, MN10300_TSCCLK);
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}
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/*
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* advance the kernel's time keeping clocks (xtime and jiffies)
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* - we use Timer 0 & 1 cascaded as a clock to nudge us the next time
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* there's a need to update
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*/
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static irqreturn_t timer_interrupt(int irq, void *dev_id)
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{
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unsigned tsc, elapse;
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write_seqlock(&xtime_lock);
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while (tsc = get_cycles(),
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elapse = mn10300_last_tsc - tsc, /* time elapsed since last
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* tick */
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elapse > MN10300_TSC_PER_HZ
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) {
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mn10300_last_tsc -= MN10300_TSC_PER_HZ;
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/* advance the kernel's time tracking system */
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profile_tick(CPU_PROFILING);
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do_timer(1);
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check_rtc_time();
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}
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write_sequnlock(&xtime_lock);
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update_process_times(user_mode(get_irq_regs()));
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return IRQ_HANDLED;
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}
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/*
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* initialise the various timers used by the main part of the kernel
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*/
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void __init time_init(void)
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{
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/* we need the prescalar running to be able to use IOCLK/8
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* - IOCLK runs at 1/4 (ST5 open) or 1/8 (ST5 closed) internal CPU clock
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* - IOCLK runs at Fosc rate (crystal speed)
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*/
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TMPSCNT |= TMPSCNT_ENABLE;
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startup_timestamp_counter();
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printk(KERN_INFO
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"timestamp counter I/O clock running at %lu.%02lu"
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" (calibrated against RTC)\n",
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MN10300_TSCCLK / 1000000, (MN10300_TSCCLK / 10000) % 100);
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xtime.tv_sec = get_initial_rtc_time();
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xtime.tv_nsec = 0;
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mn10300_last_tsc = TMTSCBC;
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/* use timer 0 & 1 cascaded to tick at as close to HZ as possible */
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setup_irq(TMJCIRQ, &timer_irq);
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set_intr_level(TMJCIRQ, TMJCICR_LEVEL);
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startup_jiffies_counter();
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#ifdef CONFIG_MN10300_WD_TIMER
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/* start the watchdog timer */
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watchdog_go();
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#endif
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mn10300_sched_clock_init();
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}
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