arch/powerpc/oprofile/cell/spu_profiler.c

   1 /*
   2  * Cell Broadband Engine OProfile Support
   3  *
   4  * (C) Copyright IBM Corporation 2006
   5  *
   6  * Authors: Maynard Johnson <maynardj@us.ibm.com>
   7  *          Carl Love <carll@us.ibm.com>
   8  *
   9  * This program is free software; you can redistribute it and/or
  10  * modify it under the terms of the GNU General Public License
  11  * as published by the Free Software Foundation; either version
  12  * 2 of the License, or (at your option) any later version.
  13  */
  14
  15 #include <linux/hrtimer.h>
  16 #include <linux/smp.h>
  17 #include <linux/slab.h>
  18 #include <asm/cell-pmu.h>
  19 #include "pr_util.h"
  20
  21 #define TRACE_ARRAY_SIZE 1024
  22 #define SCALE_SHIFT 14
  23
  24 static u32 *samples;
  25
  26 int spu_prof_running;
  27 static unsigned int profiling_interval;
  28
  29 #define NUM_SPU_BITS_TRBUF 16
  30 #define SPUS_PER_TB_ENTRY   4
  31
  32 #define SPU_PC_MASK          0xFFFF
  33
  34 static DEFINE_SPINLOCK(sample_array_lock);
  35 unsigned long sample_array_lock_flags;
  36
  37 void set_spu_profiling_frequency(unsigned int freq_khz, unsigned int cycles_reset)
  38 {
  39         unsigned long ns_per_cyc;
  40
  41         if (!freq_khz)
  42                 freq_khz = ppc_proc_freq/1000;
  43
  44         /* To calculate a timeout in nanoseconds, the basic
  45          * formula is ns = cycles_reset * (NSEC_PER_SEC / cpu frequency).
  46          * To avoid floating point math, we use the scale math
  47          * technique as described in linux/jiffies.h.  We use
  48          * a scale factor of SCALE_SHIFT, which provides 4 decimal places
  49          * of precision.  This is close enough for the purpose at hand.
  50          *
  51          * The value of the timeout should be small enough that the hw
  52          * trace buffer will not get more then about 1/3 full for the
  53          * maximum user specified (the LFSR value) hw sampling frequency.
  54          * This is to ensure the trace buffer will never fill even if the
  55          * kernel thread scheduling varies under a heavy system load.
  56          */
  57
  58         ns_per_cyc = (USEC_PER_SEC << SCALE_SHIFT)/freq_khz;
  59         profiling_interval = (ns_per_cyc * cycles_reset) >> SCALE_SHIFT;
  60
  61 }
  62
  63 /*
  64  * Extract SPU PC from trace buffer entry
  65  */
  66 static void spu_pc_extract(int cpu, int entry)
  67 {
  68         /* the trace buffer is 128 bits */
  69         u64 trace_buffer[2];
  70         u64 spu_mask;
  71         int spu;
  72
  73         spu_mask = SPU_PC_MASK;
  74
  75         /* Each SPU PC is 16 bits; hence, four spus in each of
  76          * the two 64-bit buffer entries that make up the
  77          * 128-bit trace_buffer entry.  Process two 64-bit values
  78          * simultaneously.
  79          * trace[0] SPU PC contents are: 0 1 2 3
  80          * trace[1] SPU PC contents are: 4 5 6 7
  81          */
  82
  83         cbe_read_trace_buffer(cpu, trace_buffer);
  84
  85         for (spu = SPUS_PER_TB_ENTRY-1; spu >= 0; spu--) {
  86                 /* spu PC trace entry is upper 16 bits of the
  87                  * 18 bit SPU program counter
  88                  */
  89                 samples[spu * TRACE_ARRAY_SIZE + entry]
  90                         = (spu_mask & trace_buffer[0]) << 2;
  91                 samples[(spu + SPUS_PER_TB_ENTRY) * TRACE_ARRAY_SIZE + entry]
  92                         = (spu_mask & trace_buffer[1]) << 2;
  93
  94                 trace_buffer[0] = trace_buffer[0] >> NUM_SPU_BITS_TRBUF;
  95                 trace_buffer[1] = trace_buffer[1] >> NUM_SPU_BITS_TRBUF;
  96         }
  97 }
  98
  99 static int cell_spu_pc_collection(int cpu)
 100 {
 101         u32 trace_addr;
 102         int entry;
 103
 104         /* process the collected SPU PC for the node */
 105
 106         entry = 0;
 107
 108         trace_addr = cbe_read_pm(cpu, trace_address);
 109         while (!(trace_addr & CBE_PM_TRACE_BUF_EMPTY)) {
 110                 /* there is data in the trace buffer to process */
 111                 spu_pc_extract(cpu, entry);
 112
 113                 entry++;
 114
 115                 if (entry >= TRACE_ARRAY_SIZE)
 116                         /* spu_samples is full */
 117                         break;
 118
 119                 trace_addr = cbe_read_pm(cpu, trace_address);
 120         }
 121
 122         return entry;
 123 }
 124
 125
 126 static enum hrtimer_restart profile_spus(struct hrtimer *timer)
 127 {
 128         ktime_t kt;
 129         int cpu, node, k, num_samples, spu_num;
 130
 131         if (!spu_prof_running)
 132                 goto stop;
 133
 134         for_each_online_cpu(cpu) {
 135                 if (cbe_get_hw_thread_id(cpu))
 136                         continue;
 137
 138                 node = cbe_cpu_to_node(cpu);
 139
 140                 /* There should only be one kernel thread at a time processing
 141                  * the samples.  In the very unlikely case that the processing
 142                  * is taking a very long time and multiple kernel threads are
 143                  * started to process the samples.  Make sure only one kernel
 144                  * thread is working on the samples array at a time.  The
 145                  * sample array must be loaded and then processed for a given
 146                  * cpu.  The sample array is not per cpu.
 147                  */
 148                 spin_lock_irqsave(&sample_array_lock,
 149                                   sample_array_lock_flags);
 150                 num_samples = cell_spu_pc_collection(cpu);
 151
 152                 if (num_samples == 0) {
 153                         spin_unlock_irqrestore(&sample_array_lock,
 154                                                sample_array_lock_flags);
 155                         continue;
 156                 }
 157
 158                 for (k = 0; k < SPUS_PER_NODE; k++) {
 159                         spu_num = k + (node * SPUS_PER_NODE);
 160                         spu_sync_buffer(spu_num,
 161                                         samples + (k * TRACE_ARRAY_SIZE),
 162                                         num_samples);
 163                 }
 164
 165                 spin_unlock_irqrestore(&sample_array_lock,
 166                                        sample_array_lock_flags);
 167
 168         }
 169         smp_wmb();      /* insure spu event buffer updates are written */
 170                         /* don't want events intermingled... */
 171
 172         kt = ktime_set(0, profiling_interval);
 173         if (!spu_prof_running)
 174                 goto stop;
 175         hrtimer_forward(timer, timer->base->get_time(), kt);
 176         return HRTIMER_RESTART;
 177
 178  stop:
 179         printk(KERN_INFO "SPU_PROF: spu-prof timer ending\n");
 180         return HRTIMER_NORESTART;
 181 }
 182
 183 static struct hrtimer timer;
 184 /*
 185  * Entry point for SPU profiling.
 186  * NOTE:  SPU profiling is done system-wide, not per-CPU.
 187  *
 188  * cycles_reset is the count value specified by the user when
 189  * setting up OProfile to count SPU_CYCLES.
 190  */
 191 int start_spu_profiling(unsigned int cycles_reset)
 192 {
 193         ktime_t kt;
 194
 195         pr_debug("timer resolution: %lu\n", TICK_NSEC);
 196         kt = ktime_set(0, profiling_interval);
 197         hrtimer_init(&timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 198         timer.expires = kt;
 199         timer.function = profile_spus;
 200
 201         /* Allocate arrays for collecting SPU PC samples */
 202         samples = kzalloc(SPUS_PER_NODE *
 203                           TRACE_ARRAY_SIZE * sizeof(u32), GFP_KERNEL);
 204
 205         if (!samples)
 206                 return -ENOMEM;
 207
 208         spu_prof_running = 1;
 209         hrtimer_start(&timer, kt, HRTIMER_MODE_REL);
 210         schedule_delayed_work(&spu_work, DEFAULT_TIMER_EXPIRE);
 211
 212         return 0;
 213 }
 214
 215 void stop_spu_profiling(void)
 216 {
 217         spu_prof_running = 0;
 218         hrtimer_cancel(&timer);
 219         kfree(samples);
 220         pr_debug("SPU_PROF: stop_spu_profiling issued\n");
 221 }