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 __section(".mmuoff.data.read")
  33 secondary_holding_pen_release = INVALID_HWID;
  34
  35 static phys_addr_t cpu_release_addr[NR_CPUS];
  36
  37 /*
  38  * Write secondary_holding_pen_release in a way that is guaranteed to be
  39  * visible to all observers, irrespective of whether they're taking part
  40  * in coherency or not.  This is necessary for the hotplug code to work
  41  * reliably.
  42  */
  43 static void write_pen_release(u64 val)
  44 {
  45         void *start = (void *)&secondary_holding_pen_release;
  46         unsigned long size = sizeof(secondary_holding_pen_release);
  47
  48         secondary_holding_pen_release = val;
  49         __flush_dcache_area(start, size);
  50 }
  51
  52
  53 static int smp_spin_table_cpu_init(unsigned int cpu)
  54 {
  55         struct device_node *dn;
  56         int ret;
  57
  58         dn = of_get_cpu_node(cpu, NULL);
  59         if (!dn)
  60                 return -ENODEV;
  61
  62         /*
  63          * Determine the address from which the CPU is polling.
  64          */
  65         ret = of_property_read_u64(dn, "cpu-release-addr",
  66                                    &cpu_release_addr[cpu]);
  67         if (ret)
  68                 pr_err("CPU %d: missing or invalid cpu-release-addr property\n",
  69                        cpu);
  70
  71         of_node_put(dn);
  72
  73         return ret;
  74 }
  75
  76 static int smp_spin_table_cpu_prepare(unsigned int cpu)
  77 {
  78         __le64 __iomem *release_addr;
  79
  80         if (!cpu_release_addr[cpu])
  81                 return -ENODEV;
  82
  83         /*
  84          * The cpu-release-addr may or may not be inside the linear mapping.
  85          * As ioremap_cache will either give us a new mapping or reuse the
  86          * existing linear mapping, we can use it to cover both cases. In
  87          * either case the memory will be MT_NORMAL.
  88          */
  89         release_addr = ioremap_cache(cpu_release_addr[cpu],
  90                                      sizeof(*release_addr));
  91         if (!release_addr)
  92                 return -ENOMEM;
  93
  94         /*
  95          * We write the release address as LE regardless of the native
  96          * endianess of the kernel. Therefore, any boot-loaders that
  97          * read this address need to convert this address to the
  98          * boot-loader's endianess before jumping. This is mandated by
  99          * the boot protocol.
 100          */
 101         writeq_relaxed(__pa(secondary_holding_pen), release_addr);
 102         __flush_dcache_area((__force void *)release_addr,
 103                             sizeof(*release_addr));
 104
 105         /*
 106          * Send an event to wake up the secondary CPU.
 107          */
 108         sev();
 109
 110         iounmap(release_addr);
 111
 112         return 0;
 113 }
 114
 115 static int smp_spin_table_cpu_boot(unsigned int cpu)
 116 {
 117         /*
 118          * Update the pen release flag.
 119          */
 120         write_pen_release(cpu_logical_map(cpu));
 121
 122         /*
 123          * Send an event, causing the secondaries to read pen_release.
 124          */
 125         sev();
 126
 127         return 0;
 128 }
 129
 130 const struct cpu_operations smp_spin_table_ops = {
 131         .name           = "spin-table",
 132         .cpu_init       = smp_spin_table_cpu_init,
 133         .cpu_prepare    = smp_spin_table_cpu_prepare,
 134         .cpu_boot       = smp_spin_table_cpu_boot,
 135 };