arch/arm64/kernel/suspend.c

   1 #include <linux/percpu.h>
   2 #include <linux/slab.h>
   3 #include <asm/cacheflush.h>
   4 #include <asm/debug-monitors.h>
   5 #include <asm/pgtable.h>
   6 #include <asm/memory.h>
   7 #include <asm/mmu_context.h>
   8 #include <asm/smp_plat.h>
   9 #include <asm/suspend.h>
  10 #include <asm/tlbflush.h>
  11
  12 extern int __cpu_suspend_enter(unsigned long arg, int (*fn)(unsigned long));
  13 /*
  14  * This is called by __cpu_suspend_enter() to save the state, and do whatever
  15  * flushing is required to ensure that when the CPU goes to sleep we have
  16  * the necessary data available when the caches are not searched.
  17  *
  18  * ptr: CPU context virtual address
  19  * save_ptr: address of the location where the context physical address
  20  *           must be saved
  21  */
  22 void notrace __cpu_suspend_save(struct cpu_suspend_ctx *ptr,
  23                                 phys_addr_t *save_ptr)
  24 {
  25         *save_ptr = virt_to_phys(ptr);
  26
  27         cpu_do_suspend(ptr);
  28         /*
  29          * Only flush the context that must be retrieved with the MMU
  30          * off. VA primitives ensure the flush is applied to all
  31          * cache levels so context is pushed to DRAM.
  32          */
  33         __flush_dcache_area(ptr, sizeof(*ptr));
  34         __flush_dcache_area(save_ptr, sizeof(*save_ptr));
  35 }
  36
  37 /*
  38  * This hook is provided so that cpu_suspend code can restore HW
  39  * breakpoints as early as possible in the resume path, before reenabling
  40  * debug exceptions. Code cannot be run from a CPU PM notifier since by the
  41  * time the notifier runs debug exceptions might have been enabled already,
  42  * with HW breakpoints registers content still in an unknown state.
  43  */
  44 void (*hw_breakpoint_restore)(void *);
  45 void __init cpu_suspend_set_dbg_restorer(void (*hw_bp_restore)(void *))
  46 {
  47         /* Prevent multiple restore hook initializations */
  48         if (WARN_ON(hw_breakpoint_restore))
  49                 return;
  50         hw_breakpoint_restore = hw_bp_restore;
  51 }
  52
  53 /*
  54  * cpu_suspend
  55  *
  56  * arg: argument to pass to the finisher function
  57  * fn: finisher function pointer
  58  *
  59  */
  60 int cpu_suspend(unsigned long arg, int (*fn)(unsigned long))
  61 {
  62         struct mm_struct *mm = current->active_mm;
  63         int ret;
  64         unsigned long flags;
  65
  66         /*
  67          * From this point debug exceptions are disabled to prevent
  68          * updates to mdscr register (saved and restored along with
  69          * general purpose registers) from kernel debuggers.
  70          */
  71         local_dbg_save(flags);
  72
  73         /*
  74          * mm context saved on the stack, it will be restored when
  75          * the cpu comes out of reset through the identity mapped
  76          * page tables, so that the thread address space is properly
  77          * set-up on function return.
  78          */
  79         ret = __cpu_suspend_enter(arg, fn);
  80         if (ret == 0) {
  81                 /*
  82                  * We are resuming from reset with TTBR0_EL1 set to the
  83                  * idmap to enable the MMU; restore the active_mm mappings in
  84                  * TTBR0_EL1 unless the active_mm == &init_mm, in which case
  85                  * the thread entered cpu_suspend with TTBR0_EL1 set to
  86                  * reserved TTBR0 page tables and should be restored as such.
  87                  */
  88                 if (mm == &init_mm)
  89                         cpu_set_reserved_ttbr0();
  90                 else
  91                         cpu_switch_mm(mm->pgd, mm);
  92
  93                 flush_tlb_all();
  94
  95                 /*
  96                  * Restore per-cpu offset before any kernel
  97                  * subsystem relying on it has a chance to run.
  98                  */
  99                 set_my_cpu_offset(per_cpu_offset(smp_processor_id()));
 100
 101                 /*
 102                  * Restore HW breakpoint registers to sane values
 103                  * before debug exceptions are possibly reenabled
 104                  * through local_dbg_restore.
 105                  */
 106                 if (hw_breakpoint_restore)
 107                         hw_breakpoint_restore(NULL);
 108         }
 109
 110         /*
 111          * Restore pstate flags. OS lock and mdscr have been already
 112          * restored, so from this point onwards, debugging is fully
 113          * renabled if it was enabled when core started shutdown.
 114          */
 115         local_dbg_restore(flags);
 116
 117         return ret;
 118 }
 119
 120 struct sleep_save_sp sleep_save_sp;
 121
 122 static int __init cpu_suspend_init(void)
 123 {
 124         void *ctx_ptr;
 125
 126         /* ctx_ptr is an array of physical addresses */
 127         ctx_ptr = kcalloc(mpidr_hash_size(), sizeof(phys_addr_t), GFP_KERNEL);
 128
 129         if (WARN_ON(!ctx_ptr))
 130                 return -ENOMEM;
 131
 132         sleep_save_sp.save_ptr_stash = ctx_ptr;
 133         sleep_save_sp.save_ptr_stash_phys = virt_to_phys(ctx_ptr);
 134         __flush_dcache_area(&sleep_save_sp, sizeof(struct sleep_save_sp));
 135
 136         return 0;
 137 }
 138 early_initcall(cpu_suspend_init);