arch/arm/mach-spear/platsmp.c

   1 /*
   2  * arch/arm/mach-spear13xx/platsmp.c
   3  *
   4  * based upon linux/arch/arm/mach-realview/platsmp.c
   5  *
   6  * Copyright (C) 2012 ST Microelectronics Ltd.
   7  * Shiraz Hashim <shiraz.linux.kernel@gmail.com>
   8  *
   9  * This program is free software; you can redistribute it and/or modify
  10  * it under the terms of the GNU General Public License version 2 as
  11  * published by the Free Software Foundation.
  12  */
  13
  14 #include <linux/delay.h>
  15 #include <linux/jiffies.h>
  16 #include <linux/io.h>
  17 #include <linux/smp.h>
  18 #include <asm/cacheflush.h>
  19 #include <asm/smp_scu.h>
  20 #include <mach/spear.h>
  21 #include "generic.h"
  22
  23 /*
  24  * Write pen_release in a way that is guaranteed to be visible to all
  25  * observers, irrespective of whether they're taking part in coherency
  26  * or not.  This is necessary for the hotplug code to work reliably.
  27  */
  28 static void write_pen_release(int val)
  29 {
  30         pen_release = val;
  31         smp_wmb();
  32         sync_cache_w(&pen_release);
  33 }
  34
  35 static DEFINE_SPINLOCK(boot_lock);
  36
  37 static void __iomem *scu_base = IOMEM(VA_SCU_BASE);
  38
  39 static void spear13xx_secondary_init(unsigned int cpu)
  40 {
  41         /*
  42          * let the primary processor know we're out of the
  43          * pen, then head off into the C entry point
  44          */
  45         write_pen_release(-1);
  46
  47         /*
  48          * Synchronise with the boot thread.
  49          */
  50         spin_lock(&boot_lock);
  51         spin_unlock(&boot_lock);
  52 }
  53
  54 static int spear13xx_boot_secondary(unsigned int cpu, struct task_struct *idle)
  55 {
  56         unsigned long timeout;
  57
  58         /*
  59          * set synchronisation state between this boot processor
  60          * and the secondary one
  61          */
  62         spin_lock(&boot_lock);
  63
  64         /*
  65          * The secondary processor is waiting to be released from
  66          * the holding pen - release it, then wait for it to flag
  67          * that it has been released by resetting pen_release.
  68          *
  69          * Note that "pen_release" is the hardware CPU ID, whereas
  70          * "cpu" is Linux's internal ID.
  71          */
  72         write_pen_release(cpu);
  73
  74         timeout = jiffies + (1 * HZ);
  75         while (time_before(jiffies, timeout)) {
  76                 smp_rmb();
  77                 if (pen_release == -1)
  78                         break;
  79
  80                 udelay(10);
  81         }
  82
  83         /*
  84          * now the secondary core is starting up let it run its
  85          * calibrations, then wait for it to finish
  86          */
  87         spin_unlock(&boot_lock);
  88
  89         return pen_release != -1 ? -ENOSYS : 0;
  90 }
  91
  92 /*
  93  * Initialise the CPU possible map early - this describes the CPUs
  94  * which may be present or become present in the system.
  95  */
  96 static void __init spear13xx_smp_init_cpus(void)
  97 {
  98         unsigned int i, ncores = scu_get_core_count(scu_base);
  99
 100         if (ncores > nr_cpu_ids) {
 101                 pr_warn("SMP: %u cores greater than maximum (%u), clipping\n",
 102                         ncores, nr_cpu_ids);
 103                 ncores = nr_cpu_ids;
 104         }
 105
 106         for (i = 0; i < ncores; i++)
 107                 set_cpu_possible(i, true);
 108 }
 109
 110 static void __init spear13xx_smp_prepare_cpus(unsigned int max_cpus)
 111 {
 112
 113         scu_enable(scu_base);
 114
 115         /*
 116          * Write the address of secondary startup into the system-wide location
 117          * (presently it is in SRAM). The BootMonitor waits until it receives a
 118          * soft interrupt, and then the secondary CPU branches to this address.
 119          */
 120         __raw_writel(__pa_symbol(spear13xx_secondary_startup), SYS_LOCATION);
 121 }
 122
 123 const struct smp_operations spear13xx_smp_ops __initconst = {
 124        .smp_init_cpus           = spear13xx_smp_init_cpus,
 125        .smp_prepare_cpus        = spear13xx_smp_prepare_cpus,
 126        .smp_secondary_init      = spear13xx_secondary_init,
 127        .smp_boot_secondary      = spear13xx_boot_secondary,
 128 #ifdef CONFIG_HOTPLUG_CPU
 129        .cpu_die                 = spear13xx_cpu_die,
 130 #endif
 131 };