spu_profiler.c

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/*
 * Cell Broadband Engine OProfile Support
 *
 * (C) Copyright IBM Corporation 2006
 *
 * Authors: Maynard Johnson <[email protected]>
 *      Carl Love <[email protected]>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

#include <linux/hrtimer.h>
#include <linux/smp.h>
#include <linux/slab.h>
#include <asm/cell-pmu.h>
#include <asm/time.h>
#include "pr_util.h"

#define SCALE_SHIFT 14

static u32 *samples;

/* spu_prof_running is a flag used to indicate if spu profiling is enabled
 * or not.  It is set by the routines start_spu_profiling_cycles() and
 * start_spu_profiling_events().  The flag is cleared by the routines
 * stop_spu_profiling_cycles() and stop_spu_profiling_events().  These
 * routines are called via global_start() and global_stop() which are called in
 * op_powerpc_start() and op_powerpc_stop().  These routines are called once
 * per system as a result of the user starting/stopping oprofile.  Hence, only
 * one CPU per user at a time will be changing  the value of spu_prof_running.
 * In general, OProfile does not protect against multiple users trying to run
 * OProfile at a time.
 */
int spu_prof_running;
static unsigned int profiling_interval;

#define NUM_SPU_BITS_TRBUF 16
#define SPUS_PER_TB_ENTRY   4

#define SPU_PC_MASK      0xFFFF

DEFINE_SPINLOCK(oprof_spu_smpl_arry_lck);
unsigned long oprof_spu_smpl_arry_lck_flags;

void set_spu_profiling_frequency(unsigned int freq_khz, unsigned int cycles_reset)
{
    unsigned long ns_per_cyc;

    if (!freq_khz)
        freq_khz = ppc_proc_freq/1000;

    /* To calculate a timeout in nanoseconds, the basic
     * formula is ns = cycles_reset * (NSEC_PER_SEC / cpu frequency).
     * To avoid floating point math, we use the scale math
     * technique as described in linux/jiffies.h.  We use
     * a scale factor of SCALE_SHIFT, which provides 4 decimal places
     * of precision.  This is close enough for the purpose at hand.
     *
     * The value of the timeout should be small enough that the hw
     * trace buffer will not get more than about 1/3 full for the
     * maximum user specified (the LFSR value) hw sampling frequency.
     * This is to ensure the trace buffer will never fill even if the
     * kernel thread scheduling varies under a heavy system load.
     */

    ns_per_cyc = (USEC_PER_SEC << SCALE_SHIFT)/freq_khz;
    profiling_interval = (ns_per_cyc * cycles_reset) >> SCALE_SHIFT;

}

/*
 * Extract SPU PC from trace buffer entry
 */
static void spu_pc_extract(int cpu, int entry)
{
    /* the trace buffer is 128 bits */
    u64 trace_buffer[2];
    u64 spu_mask;
    int spu;

    spu_mask = SPU_PC_MASK;

    /* Each SPU PC is 16 bits; hence, four spus in each of
     * the two 64-bit buffer entries that make up the
     * 128-bit trace_buffer entry.  Process two 64-bit values
     * simultaneously.
     * trace[0] SPU PC contents are: 0 1 2 3
     * trace[1] SPU PC contents are: 4 5 6 7
     */

    cbe_read_trace_buffer(cpu, trace_buffer);

    for (spu = SPUS_PER_TB_ENTRY-1; spu >= 0; spu--) {
        /* spu PC trace entry is upper 16 bits of the
         * 18 bit SPU program counter
         */
        samples[spu * TRACE_ARRAY_SIZE + entry]
            = (spu_mask & trace_buffer[0]) << 2;
        samples[(spu + SPUS_PER_TB_ENTRY) * TRACE_ARRAY_SIZE + entry]
            = (spu_mask & trace_buffer[1]) << 2;

        trace_buffer[0] = trace_buffer[0] >> NUM_SPU_BITS_TRBUF;
        trace_buffer[1] = trace_buffer[1] >> NUM_SPU_BITS_TRBUF;
    }
}

static int cell_spu_pc_collection(int cpu)
{
    u32 trace_addr;
    int entry;

    /* process the collected SPU PC for the node */

    entry = 0;

    trace_addr = cbe_read_pm(cpu, trace_address);
    while (!(trace_addr & CBE_PM_TRACE_BUF_EMPTY)) {
        /* there is data in the trace buffer to process */
        spu_pc_extract(cpu, entry);

        entry++;

        if (entry >= TRACE_ARRAY_SIZE)
            /* spu_samples is full */
            break;

        trace_addr = cbe_read_pm(cpu, trace_address);
    }

    return entry;
}


static enum hrtimer_restart profile_spus(struct hrtimer *timer)
{
    ktime_t kt;
    int cpu, node, k, num_samples, spu_num;

    if (!spu_prof_running)
        goto stop;

    for_each_online_cpu(cpu) {
        if (cbe_get_hw_thread_id(cpu))
            continue;

        node = cbe_cpu_to_node(cpu);

        /* There should only be one kernel thread at a time processing
         * the samples.  In the very unlikely case that the processing
         * is taking a very long time and multiple kernel threads are
         * started to process the samples.  Make sure only one kernel
         * thread is working on the samples array at a time.  The
         * sample array must be loaded and then processed for a given
         * cpu.  The sample array is not per cpu.
         */
        spin_lock_irqsave(&oprof_spu_smpl_arry_lck,
                  oprof_spu_smpl_arry_lck_flags);
        num_samples = cell_spu_pc_collection(cpu);

        if (num_samples == 0) {
            spin_unlock_irqrestore(&oprof_spu_smpl_arry_lck,
                           oprof_spu_smpl_arry_lck_flags);
            continue;
        }

        for (k = 0; k < SPUS_PER_NODE; k++) {
            spu_num = k + (node * SPUS_PER_NODE);
            spu_sync_buffer(spu_num,
                    samples + (k * TRACE_ARRAY_SIZE),
                    num_samples);
        }

        spin_unlock_irqrestore(&oprof_spu_smpl_arry_lck,
                       oprof_spu_smpl_arry_lck_flags);

    }
    smp_wmb();  /* insure spu event buffer updates are written */
            /* don't want events intermingled... */

    kt = ktime_set(0, profiling_interval);
    if (!spu_prof_running)
        goto stop;
    hrtimer_forward(timer, timer->base->get_time(), kt);
    return HRTIMER_RESTART;

 stop:
    printk(KERN_INFO "SPU_PROF: spu-prof timer ending\n");
    return HRTIMER_NORESTART;
}

static struct hrtimer timer;
/*
 * Entry point for SPU cycle profiling.
 * NOTE:  SPU profiling is done system-wide, not per-CPU.
 *
 * cycles_reset is the count value specified by the user when
 * setting up OProfile to count SPU_CYCLES.
 */
int start_spu_profiling_cycles(unsigned int cycles_reset)
{
    ktime_t kt;

    pr_debug("timer resolution: %lu\n", TICK_NSEC);
    kt = ktime_set(0, profiling_interval);
    hrtimer_init(&timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
    hrtimer_set_expires(&timer, kt);
    timer.function = profile_spus;

    /* Allocate arrays for collecting SPU PC samples */
    samples = kzalloc(SPUS_PER_NODE *
              TRACE_ARRAY_SIZE * sizeof(u32), GFP_KERNEL);

    if (!samples)
        return -ENOMEM;

    spu_prof_running = 1;
    hrtimer_start(&timer, kt, HRTIMER_MODE_REL);
    schedule_delayed_work(&spu_work, DEFAULT_TIMER_EXPIRE);

    return 0;
}

/*
 * Entry point for SPU event profiling.
 * NOTE:  SPU profiling is done system-wide, not per-CPU.
 *
 * cycles_reset is the count value specified by the user when
 * setting up OProfile to count SPU_CYCLES.
 */
void start_spu_profiling_events(void)
{
    spu_prof_running = 1;
    schedule_delayed_work(&spu_work, DEFAULT_TIMER_EXPIRE);

    return;
}

void stop_spu_profiling_cycles(void)
{
    spu_prof_running = 0;
    hrtimer_cancel(&timer);
    kfree(samples);
    pr_debug("SPU_PROF: stop_spu_profiling_cycles issued\n");
}

void stop_spu_profiling_events(void)
{
    spu_prof_running = 0;
}