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 /*
  15  * This is called by __cpu_suspend_enter() to save the state, and do whatever
  16  * flushing is required to ensure that when the CPU goes to sleep we have
  17  * the necessary data available when the caches are not searched.
  18  *
  19  * ptr: sleep_stack_data containing cpu state virtual address.
  20  * save_ptr: address of the location where the context physical address
  21  *           must be saved
  22  */
  23 void notrace __cpu_suspend_save(struct sleep_stack_data *ptr,
  24                                 phys_addr_t *save_ptr)
  25 {
  26         *save_ptr = virt_to_phys(ptr);
  27
  28         cpu_do_suspend(&ptr->system_regs);
  29         /*
  30          * Only flush the context that must be retrieved with the MMU
  31          * off. VA primitives ensure the flush is applied to all
  32          * cache levels so context is pushed to DRAM.
  33          */
  34         __flush_dcache_area(ptr, sizeof(*ptr));
  35         __flush_dcache_area(save_ptr, sizeof(*save_ptr));
  36 }
  37
  38 /*
  39  * This hook is provided so that cpu_suspend code can restore HW
  40  * breakpoints as early as possible in the resume path, before reenabling
  41  * debug exceptions. Code cannot be run from a CPU PM notifier since by the
  42  * time the notifier runs debug exceptions might have been enabled already,
  43  * with HW breakpoints registers content still in an unknown state.
  44  */
  45 static void (*hw_breakpoint_restore)(void *);
  46 void __init cpu_suspend_set_dbg_restorer(void (*hw_bp_restore)(void *))
  47 {
  48         /* Prevent multiple restore hook initializations */
  49         if (WARN_ON(hw_breakpoint_restore))
  50                 return;
  51         hw_breakpoint_restore = hw_bp_restore;
  52 }
  53
  54 void notrace __cpu_suspend_exit(void)
  55 {
  56         /*
  57          * We are resuming from reset with the idmap active in TTBR0_EL1.
  58          * We must uninstall the idmap and restore the expected MMU
  59          * state before we can possibly return to userspace.
  60          */
  61         cpu_uninstall_idmap();
  62
  63         /*
  64          * Restore per-cpu offset before any kernel
  65          * subsystem relying on it has a chance to run.
  66          */
  67         set_my_cpu_offset(per_cpu_offset(smp_processor_id()));
  68
  69         /*
  70          * Restore HW breakpoint registers to sane values
  71          * before debug exceptions are possibly reenabled
  72          * through local_dbg_restore.
  73          */
  74         if (hw_breakpoint_restore)
  75                 hw_breakpoint_restore(NULL);
  76 }
  77
  78 /*
  79  * cpu_suspend
  80  *
  81  * arg: argument to pass to the finisher function
  82  * fn: finisher function pointer
  83  *
  84  */
  85 int cpu_suspend(unsigned long arg, int (*fn)(unsigned long))
  86 {
  87         int ret = 0;
  88         unsigned long flags;
  89         struct sleep_stack_data state;
  90
  91         /*
  92          * From this point debug exceptions are disabled to prevent
  93          * updates to mdscr register (saved and restored along with
  94          * general purpose registers) from kernel debuggers.
  95          */
  96         local_dbg_save(flags);
  97
  98         /*
  99          * Function graph tracer state gets incosistent when the kernel
 100          * calls functions that never return (aka suspend finishers) hence
 101          * disable graph tracing during their execution.
 102          */
 103         pause_graph_tracing();
 104
 105         if (__cpu_suspend_enter(&state)) {
 106                 /* Call the suspend finisher */
 107                 ret = fn(arg);
 108
 109                 /*
 110                  * Never gets here, unless the suspend finisher fails.
 111                  * Successful cpu_suspend() should return from cpu_resume(),
 112                  * returning through this code path is considered an error
 113                  * If the return value is set to 0 force ret = -EOPNOTSUPP
 114                  * to make sure a proper error condition is propagated
 115                  */
 116                 if (!ret)
 117                         ret = -EOPNOTSUPP;
 118         } else {
 119                 __cpu_suspend_exit();
 120         }
 121
 122         unpause_graph_tracing();
 123
 124         /*
 125          * Restore pstate flags. OS lock and mdscr have been already
 126          * restored, so from this point onwards, debugging is fully
 127          * renabled if it was enabled when core started shutdown.
 128          */
 129         local_dbg_restore(flags);
 130
 131         return ret;
 132 }
 133
 134 struct sleep_save_sp sleep_save_sp;
 135
 136 static int __init cpu_suspend_init(void)
 137 {
 138         void *ctx_ptr;
 139
 140         /* ctx_ptr is an array of physical addresses */
 141         ctx_ptr = kcalloc(mpidr_hash_size(), sizeof(phys_addr_t), GFP_KERNEL);
 142
 143         if (WARN_ON(!ctx_ptr))
 144                 return -ENOMEM;
 145
 146         sleep_save_sp.save_ptr_stash = ctx_ptr;
 147         sleep_save_sp.save_ptr_stash_phys = virt_to_phys(ctx_ptr);
 148         __flush_dcache_area(&sleep_save_sp, sizeof(struct sleep_save_sp));
 149
 150         return 0;
 151 }
 152 early_initcall(cpu_suspend_init);