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         dcache_clean_inval_poc((unsigned long)start, (unsigned long)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         phys_addr_t pa_holding_pen = __pa_symbol(secondary_holding_pen);
  70
  71         if (!cpu_release_addr[cpu])
  72                 return -ENODEV;
  73
  74         /*
  75          * The cpu-release-addr may or may not be inside the linear mapping.
  76          * As ioremap_cache will either give us a new mapping or reuse the
  77          * existing linear mapping, we can use it to cover both cases. In
  78          * either case the memory will be MT_NORMAL.
  79          */
  80         release_addr = ioremap_cache(cpu_release_addr[cpu],
  81                                      sizeof(*release_addr));
  82         if (!release_addr)
  83                 return -ENOMEM;
  84
  85         /*
  86          * We write the release address as LE regardless of the native
  87          * endianness of the kernel. Therefore, any boot-loaders that
  88          * read this address need to convert this address to the
  89          * boot-loader's endianness before jumping. This is mandated by
  90          * the boot protocol.
  91          */
  92         writeq_relaxed(pa_holding_pen, release_addr);
  93         dcache_clean_inval_poc((__force unsigned long)release_addr,
  94                             (__force unsigned long)release_addr +
  95                                     sizeof(*release_addr));
  96
  97         /*
  98          * Send an event to wake up the secondary CPU.
  99          */
 100         sev();
 101
 102         iounmap(release_addr);
 103
 104         return 0;
 105 }
 106
 107 static int smp_spin_table_cpu_boot(unsigned int cpu)
 108 {
 109         /*
 110          * Update the pen release flag.
 111          */
 112         write_pen_release(cpu_logical_map(cpu));
 113
 114         /*
 115          * Send an event, causing the secondaries to read pen_release.
 116          */
 117         sev();
 118
 119         return 0;
 120 }
 121
 122 const struct cpu_operations smp_spin_table_ops = {
 123         .name           = "spin-table",
 124         .cpu_init       = smp_spin_table_cpu_init,
 125         .cpu_prepare    = smp_spin_table_cpu_prepare,
 126         .cpu_boot       = smp_spin_table_cpu_boot,
 127 };