Import 2.3.18pre1

[davej-history.git] / arch / sparc64 / kernel / smp.c

/* smp.c: Sparc64 SMP support.
 *
 * Copyright (C) 1997 David S. Miller (davem@caip.rutgers.edu)
 */

#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/pagemap.h>
#include <linux/threads.h>
#include <linux/smp.h>
#include <linux/smp_lock.h>
#include <linux/interrupt.h>
#include <linux/kernel_stat.h>
#include <linux/delay.h>
#include <linux/init.h>
#include <linux/spinlock.h>

#include <asm/head.h>
#include <asm/ptrace.h>
#include <asm/atomic.h>

#include <asm/irq.h>
#include <asm/page.h>
#include <asm/pgtable.h>
#include <asm/oplib.h>
#include <asm/hardirq.h>
#include <asm/softirq.h>
#include <asm/uaccess.h>
#include <asm/timer.h>

#define __KERNEL_SYSCALLS__
#include <linux/unistd.h>

extern int linux_num_cpus;
extern void calibrate_delay(void);
extern unsigned prom_cpu_nodes[];

struct cpuinfo_sparc cpu_data[NR_CPUS]  __attribute__ ((aligned (64)));

volatile int cpu_number_map[NR_CPUS]    __attribute__ ((aligned (64)));
volatile int __cpu_logical_map[NR_CPUS] __attribute__ ((aligned (64)));

/* Please don't make this stuff initdata!!!  --DaveM */
static unsigned char boot_cpu_id = 0;
static int smp_activated = 0;

/* Kernel spinlock */
spinlock_t kernel_flag = SPIN_LOCK_UNLOCKED;

volatile int smp_processors_ready = 0;
unsigned long cpu_present_map = 0;
int smp_num_cpus = 1;
int smp_threads_ready = 0;

void __init smp_setup(char *str, int *ints)
{
        /* XXX implement me XXX */
}

int smp_info(char *buf)
{
        int len = 7, i;
        
        strcpy(buf, "State:\n");
        for (i = 0; i < NR_CPUS; i++)
                if(cpu_present_map & (1UL << i))
                        len += sprintf(buf + len,
                                        "CPU%d:\t\tonline\n", i);
        return len;
}

int smp_bogo(char *buf)
{
        int len = 0, i;
        
        for (i = 0; i < NR_CPUS; i++)
                if(cpu_present_map & (1UL << i))
                        len += sprintf(buf + len,
                                       "Cpu%dBogo\t: %lu.%02lu\n",
                                       i, cpu_data[i].udelay_val / 500000,
                                       (cpu_data[i].udelay_val / 5000) % 100);
        return len;
}

void __init smp_store_cpu_info(int id)
{
        int i;

        cpu_data[id].irq_count                  = 0;
        cpu_data[id].bh_count                   = 0;
        /* multiplier and counter set by
           smp_setup_percpu_timer()  */
        cpu_data[id].udelay_val                 = loops_per_sec;

        cpu_data[id].pgcache_size               = 0;
        cpu_data[id].pte_cache                  = NULL;
        cpu_data[id].pgdcache_size              = 0;
        cpu_data[id].pgd_cache                  = NULL;
        cpu_data[id].idle_volume                = 1;

        for(i = 0; i < 16; i++)
                cpu_data[id].irq_worklists[i] = 0;
}

void __init smp_commence(void)
{
}

static void smp_setup_percpu_timer(void);
static void smp_tune_scheduling(void);

static volatile unsigned long callin_flag = 0;

extern void inherit_locked_prom_mappings(int save_p);
extern void cpu_probe(void);

void __init smp_callin(void)
{
        int cpuid = hard_smp_processor_id();

        inherit_locked_prom_mappings(0);

        __flush_cache_all();
        __flush_tlb_all();

        cpu_probe();

        /* Master did this already, now is the time for us to do it. */
        __asm__ __volatile__("
        sethi   %%hi(0x80000000), %%g1
        sllx    %%g1, 32, %%g1
        rd      %%tick, %%g2
        add     %%g2, 6, %%g2
        andn    %%g2, %%g1, %%g2
        wrpr    %%g2, 0, %%tick
"       : /* no outputs */
        : /* no inputs */
        : "g1", "g2");

        smp_setup_percpu_timer();

        __sti();

        calibrate_delay();
        smp_store_cpu_info(cpuid);
        callin_flag = 1;
        __asm__ __volatile__("membar #Sync\n\t"
                             "flush  %%g6" : : : "memory");

        /* Clear this or we will die instantly when we
         * schedule back to this idler...
         */
        current->thread.flags &= ~(SPARC_FLAG_NEWCHILD);

        /* Attach to the address space of init_task. */
        atomic_inc(&init_mm.mm_count);
        current->active_mm = &init_mm;

        while(!smp_processors_ready)
                membar("#LoadLoad");
}

extern int cpu_idle(void);
extern void init_IRQ(void);

void initialize_secondary(void)
{
}

int start_secondary(void *unused)
{
        trap_init();
        init_IRQ();
        smp_callin();
        return cpu_idle();
}

void cpu_panic(void)
{
        printk("CPU[%d]: Returns from cpu_idle!\n", smp_processor_id());
        panic("SMP bolixed\n");
}

extern struct prom_cpuinfo linux_cpus[64];

extern unsigned long smp_trampoline;

/* The OBP cpu startup callback truncates the 3rd arg cookie to
 * 32-bits (I think) so to be safe we have it read the pointer
 * contained here so we work on >4GB machines. -DaveM
 */
static struct task_struct *cpu_new_task = NULL;

void __init smp_boot_cpus(void)
{
        int cpucount = 0, i;

        printk("Entering UltraSMPenguin Mode...\n");
        __sti();
        smp_store_cpu_info(boot_cpu_id);
        smp_tune_scheduling();
        init_idle();

        if(linux_num_cpus == 1)
                return;

        for(i = 0; i < NR_CPUS; i++) {
                if(i == boot_cpu_id)
                        continue;

                if(cpu_present_map & (1UL << i)) {
                        unsigned long entry = (unsigned long)(&smp_trampoline);
                        unsigned long cookie = (unsigned long)(&cpu_new_task);
                        struct task_struct *p;
                        int timeout;
                        int no;
                        extern unsigned long phys_base;

                        entry += phys_base - KERNBASE;
                        cookie += phys_base - KERNBASE;
                        kernel_thread(start_secondary, NULL, CLONE_PID);
                        cpucount++;

                        p = init_task.prev_task;
                        init_tasks[cpucount] = p;

                        p->processor = i;
                        p->has_cpu = 1; /* we schedule the first task manually */

                        del_from_runqueue(p);
                        unhash_process(p);

                        callin_flag = 0;
                        for (no = 0; no < linux_num_cpus; no++)
                                if (linux_cpus[no].mid == i)
                                        break;
                        cpu_new_task = p;
                        prom_startcpu(linux_cpus[no].prom_node,
                                      entry, cookie);
                        for(timeout = 0; timeout < 5000000; timeout++) {
                                if(callin_flag)
                                        break;
                                udelay(100);
                        }
                        if(callin_flag) {
                                cpu_number_map[i] = cpucount;
                                __cpu_logical_map[cpucount] = i;
                                prom_cpu_nodes[i] = linux_cpus[no].prom_node;
                        } else {
                                cpucount--;
                                printk("Processor %d is stuck.\n", i);
                        }
                }
                if(!callin_flag) {
                        cpu_present_map &= ~(1UL << i);
                        cpu_number_map[i] = -1;
                }
        }
        cpu_new_task = NULL;
        if(cpucount == 0) {
                printk("Error: only one processor found.\n");
                cpu_present_map = (1UL << smp_processor_id());
        } else {
                unsigned long bogosum = 0;

                for(i = 0; i < NR_CPUS; i++) {
                        if(cpu_present_map & (1UL << i))
                                bogosum += cpu_data[i].udelay_val;
                }
                printk("Total of %d processors activated (%lu.%02lu BogoMIPS).\n",
                       cpucount + 1,
                       (bogosum + 2500)/500000,
                       ((bogosum + 2500)/5000)%100);
                smp_activated = 1;
                smp_num_cpus = cpucount + 1;
        }
        smp_processors_ready = 1;
        membar("#StoreStore | #StoreLoad");
}

/* #define XCALL_DEBUG */

static inline void xcall_deliver(u64 data0, u64 data1, u64 data2, u64 pstate, unsigned long cpu)
{
        u64 result, target = (cpu << 14) | 0x70;
        int stuck, tmp;

#ifdef XCALL_DEBUG
        printk("CPU[%d]: xcall(data[%016lx:%016lx:%016lx],tgt[%016lx])\n",
               smp_processor_id(), data0, data1, data2, target);
#endif
again:
        tmp = 0x40;
        __asm__ __volatile__("
        wrpr    %1, %2, %%pstate
        stxa    %4, [%0] %3
        stxa    %5, [%0+%8] %3
        add     %0, %8, %0
        stxa    %6, [%0+%8] %3
        membar  #Sync
        stxa    %%g0, [%7] %3
        membar  #Sync"
        : "=r" (tmp)
        : "r" (pstate), "i" (PSTATE_IE), "i" (ASI_UDB_INTR_W),
          "r" (data0), "r" (data1), "r" (data2), "r" (target), "r" (0x10), "0" (tmp));

        /* NOTE: PSTATE_IE is still clear. */
        stuck = 100000;
        do {
                __asm__ __volatile__("ldxa [%%g0] %1, %0"
                        : "=r" (result)
                        : "i" (ASI_INTR_DISPATCH_STAT));
                if(result == 0) {
                        __asm__ __volatile__("wrpr %0, 0x0, %%pstate"
                                             : : "r" (pstate));
                        return;
                }
                stuck -= 1;
                if(stuck == 0)
                        break;
        } while(result & 0x1);
        __asm__ __volatile__("wrpr %0, 0x0, %%pstate"
                             : : "r" (pstate));
        if(stuck == 0) {
#ifdef XCALL_DEBUG
                printk("CPU[%d]: mondo stuckage result[%016lx]\n",
                       smp_processor_id(), result);
#endif
        } else {
#ifdef XCALL_DEBUG
                printk("CPU[%d]: Penguin %d NACK's master.\n", smp_processor_id(), cpu);
#endif
                udelay(2);
                goto again;
        }
}

void smp_cross_call(unsigned long *func, u32 ctx, u64 data1, u64 data2)
{
        if(smp_processors_ready) {
                unsigned long mask = (cpu_present_map & ~(1UL<<smp_processor_id()));
                u64 pstate, data0 = (((u64)ctx)<<32 | (((u64)func) & 0xffffffff));
                int i, ncpus = smp_num_cpus - 1;

                __asm__ __volatile__("rdpr %%pstate, %0" : "=r" (pstate));
                for(i = 0; i < NR_CPUS; i++) {
                        if(mask & (1UL << i)) {
                                xcall_deliver(data0, data1, data2, pstate, i);
                                ncpus--;
                        }
                        if (!ncpus) break;
                }
                /* NOTE: Caller runs local copy on master. */
        }
}

extern unsigned long xcall_flush_tlb_page;
extern unsigned long xcall_flush_tlb_mm;
extern unsigned long xcall_flush_tlb_range;
extern unsigned long xcall_flush_tlb_all;
extern unsigned long xcall_tlbcachesync;
extern unsigned long xcall_flush_cache_all;
extern unsigned long xcall_report_regs;
extern unsigned long xcall_receive_signal;

void smp_receive_signal(int cpu)
{
        if(smp_processors_ready &&
           (cpu_present_map & (1UL<<cpu)) != 0) {
                u64 pstate, data0 = (((u64)&xcall_receive_signal) & 0xffffffff);
                __asm__ __volatile__("rdpr %%pstate, %0" : "=r" (pstate));
                xcall_deliver(data0, 0, 0, pstate, cpu);
        }
}

void smp_report_regs(void)
{
        smp_cross_call(&xcall_report_regs, 0, 0, 0);
}

void smp_flush_cache_all(void)
{
        smp_cross_call(&xcall_flush_cache_all, 0, 0, 0);
        __flush_cache_all();
}

void smp_flush_tlb_all(void)
{
        smp_cross_call(&xcall_flush_tlb_all, 0, 0, 0);
        __flush_tlb_all();
}

/* We know that the window frames of the user have been flushed
 * to the stack before we get here because all callers of us
 * are flush_tlb_*() routines, and these run after flush_cache_*()
 * which performs the flushw.
 *
 * XXX I diked out the fancy flush avoidance code for the
 * XXX swapping cases for now until the new MM code stabilizes. -DaveM
 *
 * The SMP TLB coherency scheme we use works as follows:
 *
 * 1) mm->cpu_vm_mask is a bit mask of which cpus an address
 *    space has (potentially) executed on, this is the heuristic
 *    we use to avoid doing cross calls.
 *
 * 2) TLB context numbers are shared globally across all processors
 *    in the system, this allows us to play several games to avoid
 *    cross calls.
 *
 *    One invariant is that when a cpu switches to a process, and
 *    that processes tsk->active_mm->cpu_vm_mask does not have the
 *    current cpu's bit set, that tlb context is flushed locally.
 *
 *    If the address space is non-shared (ie. mm->count == 1) we avoid
 *    cross calls when we want to flush the currently running process's
 *    tlb state.  This is done by clearing all cpu bits except the current
 *    processor's in current->active_mm->cpu_vm_mask and performing the
 *    flush locally only.  This will force any subsequent cpus which run
 *    this task to flush the context from the local tlb if the process
 *    migrates to another cpu (again).
 *
 * 3) For shared address spaces (threads) and swapping we bite the
 *    bullet for most cases and perform the cross call.
 *
 *    The performance gain from "optimizing" away the cross call for threads is
 *    questionable (in theory the big win for threads is the massive sharing of
 *    address space state across processors).
 *
 *    For the swapping case the locking is difficult to get right, we'd have to
 *    enforce strict ordered access to mm->cpu_vm_mask via a spinlock for example.
 *    Then again one could argue that when you are swapping, the cost of a cross
 *    call won't even show up on the performance radar.  But in any case we do get
 *    rid of the cross-call when the task has a dead context or the task has only
 *    ever run on the local cpu.
 */
void smp_flush_tlb_mm(struct mm_struct *mm)
{
        u32 ctx = CTX_HWBITS(mm->context);

        if (mm == current->active_mm &&
            atomic_read(&mm->mm_users) == 1 &&
            (mm->cpu_vm_mask == (1UL << smp_processor_id())))
                goto local_flush_and_out;

        smp_cross_call(&xcall_flush_tlb_mm, ctx, 0, 0);

local_flush_and_out:
        __flush_tlb_mm(ctx, SECONDARY_CONTEXT);
}

void smp_flush_tlb_range(struct mm_struct *mm, unsigned long start,
                         unsigned long end)
{
        u32 ctx = CTX_HWBITS(mm->context);

        start &= PAGE_MASK;
        end   &= PAGE_MASK;
        if(mm == current->active_mm &&
           atomic_read(&mm->mm_users) == 1 &&
           (mm->cpu_vm_mask == (1UL << smp_processor_id())))
                goto local_flush_and_out;

        smp_cross_call(&xcall_flush_tlb_range, ctx, start, end);

local_flush_and_out:
        __flush_tlb_range(ctx, start, SECONDARY_CONTEXT, end, PAGE_SIZE, (end-start));
}

void smp_flush_tlb_page(struct mm_struct *mm, unsigned long page)
{
        u32 ctx = CTX_HWBITS(mm->context);

        page &= PAGE_MASK;
        if(mm == current->active_mm &&
           atomic_read(&mm->mm_users) == 1 &&
           (mm->cpu_vm_mask == (1UL << smp_processor_id()))) {
                goto local_flush_and_out;
        }

        smp_cross_call(&xcall_flush_tlb_page, ctx, page, 0);

local_flush_and_out:
        __flush_tlb_page(ctx, page, SECONDARY_CONTEXT);
}

/* CPU capture. */
/* #define CAPTURE_DEBUG */
extern unsigned long xcall_capture;

static atomic_t smp_capture_depth = ATOMIC_INIT(0);
static atomic_t smp_capture_registry = ATOMIC_INIT(0);
static unsigned long penguins_are_doing_time = 0;

void smp_capture(void)
{
        if (smp_processors_ready) {
                int result = atomic_add_return(1, &smp_capture_depth);

                membar("#StoreStore | #LoadStore");
                if(result == 1) {
                        int ncpus = smp_num_cpus;

#ifdef CAPTURE_DEBUG
                        printk("CPU[%d]: Sending penguins to jail...",
                               smp_processor_id());
#endif
                        penguins_are_doing_time = 1;
                        membar("#StoreStore | #LoadStore");
                        atomic_inc(&smp_capture_registry);
                        smp_cross_call(&xcall_capture, 0, 0, 0);
                        while(atomic_read(&smp_capture_registry) != ncpus)
                                membar("#LoadLoad");
#ifdef CAPTURE_DEBUG
                        printk("done\n");
#endif
                }
        }
}

void smp_release(void)
{
        if(smp_processors_ready) {
                if(atomic_dec_and_test(&smp_capture_depth)) {
#ifdef CAPTURE_DEBUG
                        printk("CPU[%d]: Giving pardon to imprisoned penguins\n",
                               smp_processor_id());
#endif
                        penguins_are_doing_time = 0;
                        membar("#StoreStore | #StoreLoad");
                        atomic_dec(&smp_capture_registry);
                }
        }
}

/* Imprisoned penguins run with %pil == 15, but PSTATE_IE set, so they
 * can service tlb flush xcalls...
 */
void smp_penguin_jailcell(void)
{
        flushw_user();
        atomic_inc(&smp_capture_registry);
        membar("#StoreLoad | #StoreStore");
        while(penguins_are_doing_time)
                membar("#LoadLoad");
        atomic_dec(&smp_capture_registry);
}

static inline void sparc64_do_profile(unsigned long pc, unsigned long g3)
{
        if (prof_buffer && current->pid) {
                extern int _stext;
                extern int rwlock_impl_begin, rwlock_impl_end;
                extern int atomic_impl_begin, atomic_impl_end;

                if ((pc >= (unsigned long) &rwlock_impl_begin &&
                     pc < (unsigned long) &rwlock_impl_end) ||
                    (pc >= (unsigned long) &atomic_impl_begin &&
                     pc < (unsigned long) &atomic_impl_end))
                        pc = g3;

                pc -= (unsigned long) &_stext;
                pc >>= prof_shift;

                if(pc >= prof_len)
                        pc = prof_len - 1;
                atomic_inc((atomic_t *)&prof_buffer[pc]);
        }
}

static unsigned long current_tick_offset;

#define prof_multiplier(__cpu)          cpu_data[(__cpu)].multiplier
#define prof_counter(__cpu)             cpu_data[(__cpu)].counter

extern void update_one_process(struct task_struct *p, unsigned long ticks,
                               unsigned long user, unsigned long system,
                               int cpu);

void smp_percpu_timer_interrupt(struct pt_regs *regs)
{
        unsigned long compare, tick;
        int cpu = smp_processor_id();
        int user = user_mode(regs);

        /*
         * Check for level 14 softint.
         */
        if (!(get_softint() & (1UL << 0))) {
                extern void handler_irq(int, struct pt_regs *);

                handler_irq(14, regs);
                return;
        }

        clear_softint((1UL << 0));
        do {
                if(!user)
                        sparc64_do_profile(regs->tpc, regs->u_regs[UREG_G3]);
                if(!--prof_counter(cpu))
                {
                        if (cpu == boot_cpu_id) {
/* XXX Keep this in sync with irq.c --DaveM */
#define irq_enter(cpu, irq)                     \
do {    hardirq_enter(cpu);                     \
        spin_unlock_wait(&global_irq_lock);     \
} while(0)
#define irq_exit(cpu, irq)      hardirq_exit(cpu)

                                irq_enter(cpu, 0);
                                kstat.irqs[cpu][0]++;

                                timer_tick_interrupt(regs);

                                irq_exit(cpu, 0);

#undef irq_enter
#undef irq_exit
                        }

                        if(current->pid) {
                                unsigned int *inc, *inc2;

                                update_one_process(current, 1, user, !user, cpu);
                                if(--current->counter <= 0) {
                                        current->counter = 0;
                                        current->need_resched = 1;
                                }

                                if(user) {
                                        if(current->priority < DEF_PRIORITY) {
                                                inc = &kstat.cpu_nice;
                                                inc2 = &kstat.per_cpu_nice[cpu];
                                        } else {
                                                inc = &kstat.cpu_user;
                                                inc2 = &kstat.per_cpu_user[cpu];
                                        }
                                } else {
                                        inc = &kstat.cpu_system;
                                        inc2 = &kstat.per_cpu_system[cpu];
                                }
                                atomic_inc((atomic_t *)inc);
                                atomic_inc((atomic_t *)inc2);
                        }
                        prof_counter(cpu) = prof_multiplier(cpu);
                }

                __asm__ __volatile__("rd        %%tick_cmpr, %0\n\t"
                                     "add       %0, %2, %0\n\t"
                                     "wr        %0, 0x0, %%tick_cmpr\n\t"
                                     "rd        %%tick, %1"
                                     : "=&r" (compare), "=r" (tick)
                                     : "r" (current_tick_offset));
        } while (tick >= compare);
}

static void __init smp_setup_percpu_timer(void)
{
        int cpu = smp_processor_id();

        prof_counter(cpu) = prof_multiplier(cpu) = 1;

        __asm__ __volatile__("rd        %%tick, %%g1\n\t"
                             "add       %%g1, %0, %%g1\n\t"
                             "wr        %%g1, 0x0, %%tick_cmpr"
                             : /* no outputs */
                             : "r" (current_tick_offset)
                             : "g1");
}

void __init smp_tick_init(void)
{
        int i;
        
        boot_cpu_id = hard_smp_processor_id();
        current_tick_offset = timer_tick_offset;
        cpu_present_map = 0;
        for(i = 0; i < linux_num_cpus; i++)
                cpu_present_map |= (1UL << linux_cpus[i].mid);
        for(i = 0; i < NR_CPUS; i++) {
                cpu_number_map[i] = -1;
                __cpu_logical_map[i] = -1;
        }
        cpu_number_map[boot_cpu_id] = 0;
        prom_cpu_nodes[boot_cpu_id] = linux_cpus[0].prom_node;
        __cpu_logical_map[0] = boot_cpu_id;
        current->processor = boot_cpu_id;
        prof_counter(boot_cpu_id) = prof_multiplier(boot_cpu_id) = 1;
}

static inline unsigned long find_flush_base(unsigned long size)
{
        struct page *p = mem_map;
        unsigned long found, base;

        size = PAGE_ALIGN(size);
        found = size;
        base = page_address(p);
        while(found != 0) {
                /* Failure. */
                if(p >= (mem_map + max_mapnr))
                        return 0UL;
                if(PageSkip(p)) {
                        p = p->next_hash;
                        base = page_address(p);
                        found = size;
                } else {
                        found -= PAGE_SIZE;
                        p++;
                }
        }
        return base;
}

cycles_t cacheflush_time;

static void __init smp_tune_scheduling (void)
{
        unsigned long flush_base, flags, *p;
        unsigned int ecache_size;
        cycles_t tick1, tick2, raw;

        /* Approximate heuristic for SMP scheduling.  It is an
         * estimation of the time it takes to flush the L2 cache
         * on the local processor.
         *
         * The ia32 chooses to use the L1 cache flush time instead,
         * and I consider this complete nonsense.  The Ultra can service
         * a miss to the L1 with a hit to the L2 in 7 or 8 cycles, and
         * L2 misses are what create extra bus traffic (ie. the "cost"
         * of moving a process from one cpu to another).
         */
        printk("SMP: Calibrating ecache flush... ");
        ecache_size = prom_getintdefault(linux_cpus[0].prom_node,
                                         "ecache-size", (512 *1024));
        flush_base = find_flush_base(ecache_size << 1);

        if(flush_base != 0UL) {
                __save_and_cli(flags);

                /* Scan twice the size once just to get the TLB entries
                 * loaded and make sure the second scan measures pure misses.
                 */
                for(p = (unsigned long *)flush_base;
                    ((unsigned long)p) < (flush_base + (ecache_size<<1));
                    p += (64 / sizeof(unsigned long)))
                        *((volatile unsigned long *)p);

                /* Now the real measurement. */
                __asm__ __volatile__("
                b,pt    %%xcc, 1f
                 rd     %%tick, %0

                .align  64
1:              ldx     [%2 + 0x000], %%g1
                ldx     [%2 + 0x040], %%g2
                ldx     [%2 + 0x080], %%g3
                ldx     [%2 + 0x0c0], %%g5
                add     %2, 0x100, %2
                cmp     %2, %4
                bne,pt  %%xcc, 1b
                 nop
        
                rd      %%tick, %1"
                : "=&r" (tick1), "=&r" (tick2), "=&r" (flush_base)
                : "2" (flush_base), "r" (flush_base + ecache_size)
                : "g1", "g2", "g3", "g5");

                __restore_flags(flags);

                raw = (tick2 - tick1);

                /* Dampen it a little, considering two processes
                 * sharing the cache and fitting.
                 */
                cacheflush_time = (raw - (raw >> 2));
        } else
                cacheflush_time = ((ecache_size << 2) +
                                   (ecache_size << 1));

        printk("Using heuristic of %d cycles.\n",
               (int) cacheflush_time);
}

/* /proc/profile writes can call this, don't __init it please. */
int setup_profiling_timer(unsigned int multiplier)
{
        unsigned long flags;
        int i;

        if((!multiplier) || (timer_tick_offset / multiplier) < 1000)
                return -EINVAL;

        save_and_cli(flags);
        for(i = 0; i < NR_CPUS; i++) {
                if(cpu_present_map & (1UL << i))
                        prof_multiplier(i) = multiplier;
        }
        current_tick_offset = (timer_tick_offset / multiplier);
        restore_flags(flags);

        return 0;
}