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