arch/powerpc/platforms/cell/smp.c

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