arch/arm64/kernel/suspend.c

   1 #include <linux/ftrace.h>
   2 #include <linux/percpu.h>
   3 #include <linux/slab.h>
   4 #include <asm/cacheflush.h>
   5 #include <asm/debug-monitors.h>
   6 #include <asm/pgtable.h>
   7 #include <asm/memory.h>
   8 #include <asm/mmu_context.h>
   9 #include <asm/smp_plat.h>
  10 #include <asm/suspend.h>
  11 #include <asm/tlbflush.h>
  12
  13 /*
  14  * This is allocated by cpu_suspend_init(), and used to store a pointer to
  15  * the 'struct sleep_stack_data' the contains a particular CPUs state.
  16  */
  17 unsigned long *sleep_save_stash;
  18
  19 /*
  20  * This hook is provided so that cpu_suspend code can restore HW
  21  * breakpoints as early as possible in the resume path, before reenabling
  22  * debug exceptions. Code cannot be run from a CPU PM notifier since by the
  23  * time the notifier runs debug exceptions might have been enabled already,
  24  * with HW breakpoints registers content still in an unknown state.
  25  */
  26 static int (*hw_breakpoint_restore)(unsigned int);
  27 void __init cpu_suspend_set_dbg_restorer(int (*hw_bp_restore)(unsigned int))
  28 {
  29         /* Prevent multiple restore hook initializations */
  30         if (WARN_ON(hw_breakpoint_restore))
  31                 return;
  32         hw_breakpoint_restore = hw_bp_restore;
  33 }
  34
  35 void notrace __cpu_suspend_exit(void)
  36 {
  37         unsigned int cpu = smp_processor_id();
  38
  39         /*
  40          * We are resuming from reset with the idmap active in TTBR0_EL1.
  41          * We must uninstall the idmap and restore the expected MMU
  42          * state before we can possibly return to userspace.
  43          */
  44         cpu_uninstall_idmap();
  45
  46         /*
  47          * Restore per-cpu offset before any kernel
  48          * subsystem relying on it has a chance to run.
  49          */
  50         set_my_cpu_offset(per_cpu_offset(cpu));
  51
  52         /*
  53          * Restore HW breakpoint registers to sane values
  54          * before debug exceptions are possibly reenabled
  55          * through local_dbg_restore.
  56          */
  57         if (hw_breakpoint_restore)
  58                 hw_breakpoint_restore(cpu);
  59 }
  60
  61 /*
  62  * cpu_suspend
  63  *
  64  * arg: argument to pass to the finisher function
  65  * fn: finisher function pointer
  66  *
  67  */
  68 int cpu_suspend(unsigned long arg, int (*fn)(unsigned long))
  69 {
  70         int ret = 0;
  71         unsigned long flags;
  72         struct sleep_stack_data state;
  73
  74         /*
  75          * From this point debug exceptions are disabled to prevent
  76          * updates to mdscr register (saved and restored along with
  77          * general purpose registers) from kernel debuggers.
  78          */
  79         local_dbg_save(flags);
  80
  81         /*
  82          * Function graph tracer state gets incosistent when the kernel
  83          * calls functions that never return (aka suspend finishers) hence
  84          * disable graph tracing during their execution.
  85          */
  86         pause_graph_tracing();
  87
  88         if (__cpu_suspend_enter(&state)) {
  89                 /* Call the suspend finisher */
  90                 ret = fn(arg);
  91
  92                 /*
  93                  * Never gets here, unless the suspend finisher fails.
  94                  * Successful cpu_suspend() should return from cpu_resume(),
  95                  * returning through this code path is considered an error
  96                  * If the return value is set to 0 force ret = -EOPNOTSUPP
  97                  * to make sure a proper error condition is propagated
  98                  */
  99                 if (!ret)
 100                         ret = -EOPNOTSUPP;
 101         } else {
 102                 __cpu_suspend_exit();
 103         }
 104
 105         unpause_graph_tracing();
 106
 107         /*
 108          * Restore pstate flags. OS lock and mdscr have been already
 109          * restored, so from this point onwards, debugging is fully
 110          * renabled if it was enabled when core started shutdown.
 111          */
 112         local_dbg_restore(flags);
 113
 114         return ret;
 115 }
 116
 117 static int __init cpu_suspend_init(void)
 118 {
 119         /* ctx_ptr is an array of physical addresses */
 120         sleep_save_stash = kcalloc(mpidr_hash_size(), sizeof(*sleep_save_stash),
 121                                    GFP_KERNEL);
 122
 123         if (WARN_ON(!sleep_save_stash))
 124                 return -ENOMEM;
 125
 126         return 0;
 127 }
 128 early_initcall(cpu_suspend_init);