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Linux/arch/arm/mach-spear/platsmp.c

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  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(virt_to_phys(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 };
132 

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