arch/powerpc/platforms/cell/smp.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * SMP support for BPA machines.
   4  *
   5  * Dave Engebretsen, Peter Bergner, and
   6  * Mike Corrigan {engebret|bergner|mikec}@us.ibm.com
   7  *
   8  * Plus various changes from other IBM teams...
   9  */
  10
  11 #undef DEBUG
  12
  13 #include <linux/kernel.h>
  14 #include <linux/sched.h>
  15 #include <linux/smp.h>
  16 #include <linux/interrupt.h>
  17 #include <linux/delay.h>
  18 #include <linux/init.h>
  19 #include <linux/spinlock.h>
  20 #include <linux/cache.h>
  21 #include <linux/err.h>
  22 #include <linux/device.h>
  23 #include <linux/cpu.h>
  24
  25 #include <asm/ptrace.h>
  26 #include <linux/atomic.h>
  27 #include <asm/irq.h>
  28 #include <asm/page.h>
  29 #include <asm/pgtable.h>
  30 #include <asm/io.h>
  31 #include <asm/prom.h>
  32 #include <asm/smp.h>
  33 #include <asm/paca.h>
  34 #include <asm/machdep.h>
  35 #include <asm/cputable.h>
  36 #include <asm/firmware.h>
  37 #include <asm/rtas.h>
  38 #include <asm/cputhreads.h>
  39 #include <asm/code-patching.h>
  40
  41 #include "interrupt.h"
  42 #include <asm/udbg.h>
  43
  44 #ifdef DEBUG
  45 #define DBG(fmt...) udbg_printf(fmt)
  46 #else
  47 #define DBG(fmt...)
  48 #endif
  49
  50 /*
  51  * The Primary thread of each non-boot processor was started from the OF client
  52  * interface by prom_hold_cpus and is spinning on secondary_hold_spinloop.
  53  */
  54 static cpumask_t of_spin_map;
  55
  56 /**
  57  * smp_startup_cpu() - start the given cpu
  58  *
  59  * At boot time, there is nothing to do for primary threads which were
  60  * started from Open Firmware.  For anything else, call RTAS with the
  61  * appropriate start location.
  62  *
  63  * Returns:
  64  *      0       - failure
  65  *      1       - success
  66  */
  67 static inline int smp_startup_cpu(unsigned int lcpu)
  68 {
  69         int status;
  70         unsigned long start_here =
  71                         __pa(ppc_function_entry(generic_secondary_smp_init));
  72         unsigned int pcpu;
  73         int start_cpu;
  74
  75         if (cpumask_test_cpu(lcpu, &of_spin_map))
  76                 /* Already started by OF and sitting in spin loop */
  77                 return 1;
  78
  79         pcpu = get_hard_smp_processor_id(lcpu);
  80
  81         /* Fixup atomic count: it exited inside IRQ handler. */
  82         task_thread_info(paca_ptrs[lcpu]->__current)->preempt_count     = 0;
  83
  84         /*
  85          * If the RTAS start-cpu token does not exist then presume the
  86          * cpu is already spinning.
  87          */
  88         start_cpu = rtas_token("start-cpu");
  89         if (start_cpu == RTAS_UNKNOWN_SERVICE)
  90                 return 1;
  91
  92         status = rtas_call(start_cpu, 3, 1, NULL, pcpu, start_here, lcpu);
  93         if (status != 0) {
  94                 printk(KERN_ERR "start-cpu failed: %i\n", status);
  95                 return 0;
  96         }
  97
  98         return 1;
  99 }
 100
 101 static void smp_cell_setup_cpu(int cpu)
 102 {
 103         if (cpu != boot_cpuid)
 104                 iic_setup_cpu();
 105
 106         /*
 107          * change default DABRX to allow user watchpoints
 108          */
 109         mtspr(SPRN_DABRX, DABRX_KERNEL | DABRX_USER);
 110 }
 111
 112 static int smp_cell_kick_cpu(int nr)
 113 {
 114         if (nr < 0 || nr >= nr_cpu_ids)
 115                 return -EINVAL;
 116
 117         if (!smp_startup_cpu(nr))
 118                 return -ENOENT;
 119
 120         /*
 121          * The processor is currently spinning, waiting for the
 122          * cpu_start field to become non-zero After we set cpu_start,
 123          * the processor will continue on to secondary_start
 124          */
 125         paca_ptrs[nr]->cpu_start = 1;
 126
 127         return 0;
 128 }
 129
 130 static struct smp_ops_t bpa_iic_smp_ops = {
 131         .message_pass   = iic_message_pass,
 132         .probe          = iic_request_IPIs,
 133         .kick_cpu       = smp_cell_kick_cpu,
 134         .setup_cpu      = smp_cell_setup_cpu,
 135         .cpu_bootable   = smp_generic_cpu_bootable,
 136 };
 137
 138 /* This is called very early */
 139 void __init smp_init_cell(void)
 140 {
 141         int i;
 142
 143         DBG(" -> smp_init_cell()\n");
 144
 145         smp_ops = &bpa_iic_smp_ops;
 146
 147         /* Mark threads which are still spinning in hold loops. */
 148         if (cpu_has_feature(CPU_FTR_SMT)) {
 149                 for_each_present_cpu(i) {
 150                         if (cpu_thread_in_core(i) == 0)
 151                                 cpumask_set_cpu(i, &of_spin_map);
 152                 }
 153         } else
 154                 cpumask_copy(&of_spin_map, cpu_present_mask);
 155
 156         cpumask_clear_cpu(boot_cpuid, &of_spin_map);
 157
 158         /* Non-lpar has additional take/give timebase */
 159         if (rtas_token("freeze-time-base") != RTAS_UNKNOWN_SERVICE) {
 160                 smp_ops->give_timebase = rtas_give_timebase;
 161                 smp_ops->take_timebase = rtas_take_timebase;
 162         }
 163
 164         DBG(" <- smp_init_cell()\n");
 165 }