arch/arm64/kernel/smp_spin_table.c

   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
  32 extern void secondary_holding_pen(void);
  33 volatile unsigned long __section(".mmuoff.data.read")
  34 secondary_holding_pen_release = INVALID_HWID;
  35
  36 static 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  */
  44 static 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
  54 static 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
  77 static 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
 116 static 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
 131 const 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 };