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 void (*hw_breakpoint_restore)(void *);
  27 void __init cpu_suspend_set_dbg_restorer(void (*hw_bp_restore)(void *))
  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         /*
  38          * We are resuming from reset with the idmap active in TTBR0_EL1.
  39          * We must uninstall the idmap and restore the expected MMU
  40          * state before we can possibly return to userspace.
  41          */
  42         cpu_uninstall_idmap();
  43
  44         /*
  45          * Restore per-cpu offset before any kernel
  46          * subsystem relying on it has a chance to run.
  47          */
  48         set_my_cpu_offset(per_cpu_offset(smp_processor_id()));
  49
  50         /*
  51          * Restore HW breakpoint registers to sane values
  52          * before debug exceptions are possibly reenabled
  53          * through local_dbg_restore.
  54          */
  55         if (hw_breakpoint_restore)
  56                 hw_breakpoint_restore(NULL);
  57 }
  58
  59 /*
  60  * cpu_suspend
  61  *
  62  * arg: argument to pass to the finisher function
  63  * fn: finisher function pointer
  64  *
  65  */
  66 int cpu_suspend(unsigned long arg, int (*fn)(unsigned long))
  67 {
  68         int ret = 0;
  69         unsigned long flags;
  70         struct sleep_stack_data state;
  71
  72         /*
  73          * From this point debug exceptions are disabled to prevent
  74          * updates to mdscr register (saved and restored along with
  75          * general purpose registers) from kernel debuggers.
  76          */
  77         local_dbg_save(flags);
  78
  79         /*
  80          * Function graph tracer state gets incosistent when the kernel
  81          * calls functions that never return (aka suspend finishers) hence
  82          * disable graph tracing during their execution.
  83          */
  84         pause_graph_tracing();
  85
  86         if (__cpu_suspend_enter(&state)) {
  87                 /* Call the suspend finisher */
  88                 ret = fn(arg);
  89
  90                 /*
  91                  * Never gets here, unless the suspend finisher fails.
  92                  * Successful cpu_suspend() should return from cpu_resume(),
  93                  * returning through this code path is considered an error
  94                  * If the return value is set to 0 force ret = -EOPNOTSUPP
  95                  * to make sure a proper error condition is propagated
  96                  */
  97                 if (!ret)
  98                         ret = -EOPNOTSUPP;
  99         } else {
 100                 __cpu_suspend_exit();
 101         }
 102
 103         unpause_graph_tracing();
 104
 105         /*
 106          * Restore pstate flags. OS lock and mdscr have been already
 107          * restored, so from this point onwards, debugging is fully
 108          * renabled if it was enabled when core started shutdown.
 109          */
 110         local_dbg_restore(flags);
 111
 112         return ret;
 113 }
 114
 115 static int __init cpu_suspend_init(void)
 116 {
 117         /* ctx_ptr is an array of physical addresses */
 118         sleep_save_stash = kcalloc(mpidr_hash_size(), sizeof(*sleep_save_stash),
 119                                    GFP_KERNEL);
 120
 121         if (WARN_ON(!sleep_save_stash))
 122                 return -ENOMEM;
 123
 124         return 0;
 125 }
 126 early_initcall(cpu_suspend_init);