LXR linux/arch/arm64/kernel/smp_spin

   1/*
   2 * Spin Table SMP initialisation
   3 *
   4 * Copyright (C) 2013 ARM Ltd.
   5 *
   6 * This program is free software; you can redistribute it and/or modify
   7 * it under the terms of the GNU General Public License version 2 as
   8 * published by the Free Software Foundation.
   9 *
  10 * This program is distributed in the hope that it will be useful,
  11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13 * GNU General Public License for more details.
  14 *
  15 * You should have received a copy of the GNU General Public License
  16 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  17 */
  18
  19#include <linux/delay.h>
  20#include <linux/init.h>
  21#include <linux/of.h>
  22#include <linux/smp.h>
  23#include <linux/types.h>
  24#include <linux/mm.h>
  25
  26#include <asm/cacheflush.h>
  27#include <asm/cpu_ops.h>
  28#include <asm/cputype.h>
  29#include <asm/io.h>
  30#include <asm/smp_plat.h>
  31
  32extern void secondary_holding_pen(void);
  33volatile unsigned long __section(".mmuoff.data.read")
  34secondary_holding_pen_release = INVALID_HWID;
  35
  36static phys_addr_t cpu_release_addr[NR_CPUS];
  37
  38/*
  39 * Write secondary_holding_pen_release in a way that is guaranteed to be
  40 * visible to all observers, irrespective of whether they're taking part
  41 * in coherency or not.  This is necessary for the hotplug code to work
  42 * reliably.
  43 */
  44static void write_pen_release(u64 val)
  45{
  46        void *start = (void *)&secondary_holding_pen_release;
  47        unsigned long size = sizeof(secondary_holding_pen_release);
  48
  49        secondary_holding_pen_release = val;
  50        __flush_dcache_area(start, size);
  51}
  52
  53
  54static int smp_spin_table_cpu_init(unsigned int cpu)
  55{
  56        struct device_node *dn;
  57        int ret;
  58
  59        dn = of_get_cpu_node(cpu, NULL);
  60        if (!dn)
  61                return -ENODEV;
  62
  63        /*
  64         * Determine the address from which the CPU is polling.
  65         */
  66        ret = of_property_read_u64(dn, "cpu-release-addr",
  67                                   &cpu_release_addr[cpu]);
  68        if (ret)
  69                pr_err("CPU %d: missing or invalid cpu-release-addr property\n",
  70                       cpu);
  71
  72        of_node_put(dn);
  73
  74        return ret;
  75}
  76
  77static int smp_spin_table_cpu_prepare(unsigned int cpu)
  78{
  79        __le64 __iomem *release_addr;
  80
  81        if (!cpu_release_addr[cpu])
  82                return -ENODEV;
  83
  84        /*
  85         * The cpu-release-addr may or may not be inside the linear mapping.
  86         * As ioremap_cache will either give us a new mapping or reuse the
  87         * existing linear mapping, we can use it to cover both cases. In
  88         * either case the memory will be MT_NORMAL.
  89         */
  90        release_addr = ioremap_cache(cpu_release_addr[cpu],
  91                                     sizeof(*release_addr));
  92        if (!release_addr)
  93                return -ENOMEM;
  94
  95        /*
  96         * We write the release address as LE regardless of the native
  97         * endianess of the kernel. Therefore, any boot-loaders that
  98         * read this address need to convert this address to the
  99         * boot-loader's endianess before jumping. This is mandated by
 100         * the boot protocol.
 101         */
 102        writeq_relaxed(__pa_symbol(secondary_holding_pen), release_addr);
 103        __flush_dcache_area((__force void *)release_addr,
 104                            sizeof(*release_addr));
 105
 106        /*
 107         * Send an event to wake up the secondary CPU.
 108         */
 109        sev();
 110
 111        iounmap(release_addr);
 112
 113        return 0;
 114}
 115
 116static int smp_spin_table_cpu_boot(unsigned int cpu)
 117{
 118        /*
 119         * Update the pen release flag.
 120         */
 121        write_pen_release(cpu_logical_map(cpu));
 122
 123        /*
 124         * Send an event, causing the secondaries to read pen_release.
 125         */
 126        sev();
 127
 128        return 0;
 129}
 130
 131const struct cpu_operations smp_spin_table_ops = {
 132        .name           = "spin-table",
 133        .cpu_init       = smp_spin_table_cpu_init,
 134        .cpu_prepare    = smp_spin_table_cpu_prepare,
 135        .cpu_boot       = smp_spin_table_cpu_boot,
 136};
 137