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
  25 #include <asm/cacheflush.h>
  26 #include <asm/cpu_ops.h>
  27 #include <asm/cputype.h>
  28 #include <asm/io.h>
  29 #include <asm/smp_plat.h>
  30
  31 extern void secondary_holding_pen(void);
  32 volatile unsigned long secondary_holding_pen_release = INVALID_HWID;
  33
  34 static phys_addr_t cpu_release_addr[NR_CPUS];
  35
  36 /*
  37  * Write secondary_holding_pen_release in a way that is guaranteed to be
  38  * visible to all observers, irrespective of whether they're taking part
  39  * in coherency or not.  This is necessary for the hotplug code to work
  40  * reliably.
  41  */
  42 static void write_pen_release(u64 val)
  43 {
  44         void *start = (void *)&secondary_holding_pen_release;
  45         unsigned long size = sizeof(secondary_holding_pen_release);
  46
  47         secondary_holding_pen_release = val;
  48         __flush_dcache_area(start, size);
  49 }
  50
  51
  52 static int smp_spin_table_cpu_init(unsigned int cpu)
  53 {
  54         struct device_node *dn;
  55         int ret;
  56
  57         dn = of_get_cpu_node(cpu, NULL);
  58         if (!dn)
  59                 return -ENODEV;
  60
  61         /*
  62          * Determine the address from which the CPU is polling.
  63          */
  64         ret = of_property_read_u64(dn, "cpu-release-addr",
  65                                    &cpu_release_addr[cpu]);
  66         if (ret)
  67                 pr_err("CPU %d: missing or invalid cpu-release-addr property\n",
  68                        cpu);
  69
  70         of_node_put(dn);
  71
  72         return ret;
  73 }
  74
  75 static int smp_spin_table_cpu_prepare(unsigned int cpu)
  76 {
  77         __le64 __iomem *release_addr;
  78
  79         if (!cpu_release_addr[cpu])
  80                 return -ENODEV;
  81
  82         /*
  83          * The cpu-release-addr may or may not be inside the linear mapping.
  84          * As ioremap_cache will either give us a new mapping or reuse the
  85          * existing linear mapping, we can use it to cover both cases. In
  86          * either case the memory will be MT_NORMAL.
  87          */
  88         release_addr = ioremap_cache(cpu_release_addr[cpu],
  89                                      sizeof(*release_addr));
  90         if (!release_addr)
  91                 return -ENOMEM;
  92
  93         /*
  94          * We write the release address as LE regardless of the native
  95          * endianess of the kernel. Therefore, any boot-loaders that
  96          * read this address need to convert this address to the
  97          * boot-loader's endianess before jumping. This is mandated by
  98          * the boot protocol.
  99          */
 100         writeq_relaxed(__pa(secondary_holding_pen), release_addr);
 101         __flush_dcache_area((__force void *)release_addr,
 102                             sizeof(*release_addr));
 103
 104         /*
 105          * Send an event to wake up the secondary CPU.
 106          */
 107         sev();
 108
 109         iounmap(release_addr);
 110
 111         return 0;
 112 }
 113
 114 static int smp_spin_table_cpu_boot(unsigned int cpu)
 115 {
 116         /*
 117          * Update the pen release flag.
 118          */
 119         write_pen_release(cpu_logical_map(cpu));
 120
 121         /*
 122          * Send an event, causing the secondaries to read pen_release.
 123          */
 124         sev();
 125
 126         return 0;
 127 }
 128
 129 const struct cpu_operations smp_spin_table_ops = {
 130         .name           = "spin-table",
 131         .cpu_init       = smp_spin_table_cpu_init,
 132         .cpu_prepare    = smp_spin_table_cpu_prepare,
 133         .cpu_boot       = smp_spin_table_cpu_boot,
 134 };