arch/arm64/kernel/smp_spin_table.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Spin Table SMP initialisation
   4  *
   5  * Copyright (C) 2013 ARM Ltd.
   6  */
   7
   8 #include <linux/delay.h>
   9 #include <linux/init.h>
  10 #include <linux/of.h>
  11 #include <linux/smp.h>
  12 #include <linux/types.h>
  13 #include <linux/mm.h>
  14
  15 #include <asm/cacheflush.h>
  16 #include <asm/cpu_ops.h>
  17 #include <asm/cputype.h>
  18 #include <asm/io.h>
  19 #include <asm/smp_plat.h>
  20
  21 extern void secondary_holding_pen(void);
  22 volatile unsigned long __section(".mmuoff.data.read")
  23 secondary_holding_pen_release = INVALID_HWID;
  24
  25 static phys_addr_t cpu_release_addr[NR_CPUS];
  26
  27 /*
  28  * Write secondary_holding_pen_release in a way that is guaranteed to be
  29  * visible to all observers, irrespective of whether they're taking part
  30  * in coherency or not.  This is necessary for the hotplug code to work
  31  * reliably.
  32  */
  33 static void write_pen_release(u64 val)
  34 {
  35         void *start = (void *)&secondary_holding_pen_release;
  36         unsigned long size = sizeof(secondary_holding_pen_release);
  37
  38         secondary_holding_pen_release = val;
  39         __flush_dcache_area(start, size);
  40 }
  41
  42
  43 static int smp_spin_table_cpu_init(unsigned int cpu)
  44 {
  45         struct device_node *dn;
  46         int ret;
  47
  48         dn = of_get_cpu_node(cpu, NULL);
  49         if (!dn)
  50                 return -ENODEV;
  51
  52         /*
  53          * Determine the address from which the CPU is polling.
  54          */
  55         ret = of_property_read_u64(dn, "cpu-release-addr",
  56                                    &cpu_release_addr[cpu]);
  57         if (ret)
  58                 pr_err("CPU %d: missing or invalid cpu-release-addr property\n",
  59                        cpu);
  60
  61         of_node_put(dn);
  62
  63         return ret;
  64 }
  65
  66 static int smp_spin_table_cpu_prepare(unsigned int cpu)
  67 {
  68         __le64 __iomem *release_addr;
  69
  70         if (!cpu_release_addr[cpu])
  71                 return -ENODEV;
  72
  73         /*
  74          * The cpu-release-addr may or may not be inside the linear mapping.
  75          * As ioremap_cache will either give us a new mapping or reuse the
  76          * existing linear mapping, we can use it to cover both cases. In
  77          * either case the memory will be MT_NORMAL.
  78          */
  79         release_addr = ioremap_cache(cpu_release_addr[cpu],
  80                                      sizeof(*release_addr));
  81         if (!release_addr)
  82                 return -ENOMEM;
  83
  84         /*
  85          * We write the release address as LE regardless of the native
  86          * endianess of the kernel. Therefore, any boot-loaders that
  87          * read this address need to convert this address to the
  88          * boot-loader's endianess before jumping. This is mandated by
  89          * the boot protocol.
  90          */
  91         writeq_relaxed(__pa_symbol(secondary_holding_pen), release_addr);
  92         __flush_dcache_area((__force void *)release_addr,
  93                             sizeof(*release_addr));
  94
  95         /*
  96          * Send an event to wake up the secondary CPU.
  97          */
  98         sev();
  99
 100         iounmap(release_addr);
 101
 102         return 0;
 103 }
 104
 105 static int smp_spin_table_cpu_boot(unsigned int cpu)
 106 {
 107         /*
 108          * Update the pen release flag.
 109          */
 110         write_pen_release(cpu_logical_map(cpu));
 111
 112         /*
 113          * Send an event, causing the secondaries to read pen_release.
 114          */
 115         sev();
 116
 117         return 0;
 118 }
 119
 120 const struct cpu_operations smp_spin_table_ops = {
 121         .name           = "spin-table",
 122         .cpu_init       = smp_spin_table_cpu_init,
 123         .cpu_prepare    = smp_spin_table_cpu_prepare,
 124         .cpu_boot       = smp_spin_table_cpu_boot,
 125 };