linux/arch/powerpc/platforms/cell/smp.c
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   1/*
   2 * SMP support for BPA machines.
   3 *
   4 * Dave Engebretsen, Peter Bergner, and
   5 * Mike Corrigan {engebret|bergner|mikec}@us.ibm.com
   6 *
   7 * Plus various changes from other IBM teams...
   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#undef DEBUG
  16
  17#include <linux/kernel.h>
  18#include <linux/sched.h>
  19#include <linux/smp.h>
  20#include <linux/interrupt.h>
  21#include <linux/delay.h>
  22#include <linux/init.h>
  23#include <linux/spinlock.h>
  24#include <linux/cache.h>
  25#include <linux/err.h>
  26#include <linux/device.h>
  27#include <linux/cpu.h>
  28
  29#include <asm/ptrace.h>
  30#include <linux/atomic.h>
  31#include <asm/irq.h>
  32#include <asm/page.h>
  33#include <asm/pgtable.h>
  34#include <asm/io.h>
  35#include <asm/prom.h>
  36#include <asm/smp.h>
  37#include <asm/paca.h>
  38#include <asm/machdep.h>
  39#include <asm/cputable.h>
  40#include <asm/firmware.h>
  41#include <asm/system.h>
  42#include <asm/rtas.h>
  43#include <asm/cputhreads.h>
  44
  45#include "interrupt.h"
  46#include <asm/udbg.h>
  47
  48#ifdef DEBUG
  49#define DBG(fmt...) udbg_printf(fmt)
  50#else
  51#define DBG(fmt...)
  52#endif
  53
  54/*
  55 * The Primary thread of each non-boot processor was started from the OF client
  56 * interface by prom_hold_cpus and is spinning on secondary_hold_spinloop.
  57 */
  58static cpumask_t of_spin_map;
  59
  60/**
  61 * smp_startup_cpu() - start the given cpu
  62 *
  63 * At boot time, there is nothing to do for primary threads which were
  64 * started from Open Firmware.  For anything else, call RTAS with the
  65 * appropriate start location.
  66 *
  67 * Returns:
  68 *      0       - failure
  69 *      1       - success
  70 */
  71static inline int __devinit smp_startup_cpu(unsigned int lcpu)
  72{
  73        int status;
  74        unsigned long start_here = __pa((u32)*((unsigned long *)
  75                                               generic_secondary_smp_init));
  76        unsigned int pcpu;
  77        int start_cpu;
  78
  79        if (cpumask_test_cpu(lcpu, &of_spin_map))
  80                /* Already started by OF and sitting in spin loop */
  81                return 1;
  82
  83        pcpu = get_hard_smp_processor_id(lcpu);
  84
  85        /* Fixup atomic count: it exited inside IRQ handler. */
  86        task_thread_info(paca[lcpu].__current)->preempt_count   = 0;
  87
  88        /*
  89         * If the RTAS start-cpu token does not exist then presume the
  90         * cpu is already spinning.
  91         */
  92        start_cpu = rtas_token("start-cpu");
  93        if (start_cpu == RTAS_UNKNOWN_SERVICE)
  94                return 1;
  95
  96        status = rtas_call(start_cpu, 3, 1, NULL, pcpu, start_here, lcpu);
  97        if (status != 0) {
  98                printk(KERN_ERR "start-cpu failed: %i\n", status);
  99                return 0;
 100        }
 101
 102        return 1;
 103}
 104
 105static int __init smp_iic_probe(void)
 106{
 107        iic_request_IPIs();
 108
 109        return cpumask_weight(cpu_possible_mask);
 110}
 111
 112static void __devinit smp_cell_setup_cpu(int cpu)
 113{
 114        if (cpu != boot_cpuid)
 115                iic_setup_cpu();
 116
 117        /*
 118         * change default DABRX to allow user watchpoints
 119         */
 120        mtspr(SPRN_DABRX, DABRX_KERNEL | DABRX_USER);
 121}
 122
 123static int __devinit smp_cell_kick_cpu(int nr)
 124{
 125        BUG_ON(nr < 0 || nr >= NR_CPUS);
 126
 127        if (!smp_startup_cpu(nr))
 128                return -ENOENT;
 129
 130        /*
 131         * The processor is currently spinning, waiting for the
 132         * cpu_start field to become non-zero After we set cpu_start,
 133         * the processor will continue on to secondary_start
 134         */
 135        paca[nr].cpu_start = 1;
 136
 137        return 0;
 138}
 139
 140static int smp_cell_cpu_bootable(unsigned int nr)
 141{
 142        /* Special case - we inhibit secondary thread startup
 143         * during boot if the user requests it.  Odd-numbered
 144         * cpus are assumed to be secondary threads.
 145         */
 146        if (system_state < SYSTEM_RUNNING &&
 147            cpu_has_feature(CPU_FTR_SMT) &&
 148            !smt_enabled_at_boot && cpu_thread_in_core(nr) != 0)
 149                return 0;
 150
 151        return 1;
 152}
 153static struct smp_ops_t bpa_iic_smp_ops = {
 154        .message_pass   = iic_message_pass,
 155        .probe          = smp_iic_probe,
 156        .kick_cpu       = smp_cell_kick_cpu,
 157        .setup_cpu      = smp_cell_setup_cpu,
 158        .cpu_bootable   = smp_cell_cpu_bootable,
 159};
 160
 161/* This is called very early */
 162void __init smp_init_cell(void)
 163{
 164        int i;
 165
 166        DBG(" -> smp_init_cell()\n");
 167
 168        smp_ops = &bpa_iic_smp_ops;
 169
 170        /* Mark threads which are still spinning in hold loops. */
 171        if (cpu_has_feature(CPU_FTR_SMT)) {
 172                for_each_present_cpu(i) {
 173                        if (cpu_thread_in_core(i) == 0)
 174                                cpumask_set_cpu(i, &of_spin_map);
 175                }
 176        } else
 177                cpumask_copy(&of_spin_map, cpu_present_mask);
 178
 179        cpumask_clear_cpu(boot_cpuid, &of_spin_map);
 180
 181        /* Non-lpar has additional take/give timebase */
 182        if (rtas_token("freeze-time-base") != RTAS_UNKNOWN_SERVICE) {
 183                smp_ops->give_timebase = rtas_give_timebase;
 184                smp_ops->take_timebase = rtas_take_timebase;
 185        }
 186
 187        DBG(" <- smp_init_cell()\n");
 188}
 189