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/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  */
  58 static 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  */
  71 static 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
 105 static int __init smp_iic_probe(void)
 106 {
 107         iic_request_IPIs();
 108
 109         return cpumask_weight(cpu_possible_mask);
 110 }
 111
 112 static 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
 123 static 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
 140 static 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 }
 153 static 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 */
 162 void __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 }