arch/arm64/kernel/suspend.c

   1 #include <linux/percpu.h>
   2 #include <linux/slab.h>
   3 #include <asm/cacheflush.h>
   4 #include <asm/cpu_ops.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 extern int __cpu_suspend_enter(unsigned long arg, int (*fn)(unsigned long));
  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: CPU context 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 cpu_suspend_ctx *ptr,
  24                                 phys_addr_t *save_ptr)
  25 {
  26         *save_ptr = virt_to_phys(ptr);
  27
  28         cpu_do_suspend(ptr);
  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 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 /**
  55  * cpu_suspend() - function to enter a low-power state
  56  * @arg: argument to pass to CPU suspend operations
  57  *
  58  * Return: 0 on success, -EOPNOTSUPP if CPU suspend hook not initialized, CPU
  59  * operations back-end error code otherwise.
  60  */
  61 int cpu_suspend(unsigned long arg)
  62 {
  63         int cpu = smp_processor_id();
  64
  65         /*
  66          * If cpu_ops have not been registered or suspend
  67          * has not been initialized, cpu_suspend call fails early.
  68          */
  69         if (!cpu_ops[cpu] || !cpu_ops[cpu]->cpu_suspend)
  70                 return -EOPNOTSUPP;
  71         return cpu_ops[cpu]->cpu_suspend(arg);
  72 }
  73
  74 /*
  75  * __cpu_suspend
  76  *
  77  * arg: argument to pass to the finisher function
  78  * fn: finisher function pointer
  79  *
  80  */
  81 int __cpu_suspend(unsigned long arg, int (*fn)(unsigned long))
  82 {
  83         struct mm_struct *mm = current->active_mm;
  84         int ret;
  85         unsigned long flags;
  86
  87         /*
  88          * From this point debug exceptions are disabled to prevent
  89          * updates to mdscr register (saved and restored along with
  90          * general purpose registers) from kernel debuggers.
  91          */
  92         local_dbg_save(flags);
  93
  94         /*
  95          * mm context saved on the stack, it will be restored when
  96          * the cpu comes out of reset through the identity mapped
  97          * page tables, so that the thread address space is properly
  98          * set-up on function return.
  99          */
 100         ret = __cpu_suspend_enter(arg, fn);
 101         if (ret == 0) {
 102                 /*
 103                  * We are resuming from reset with TTBR0_EL1 set to the
 104                  * idmap to enable the MMU; restore the active_mm mappings in
 105                  * TTBR0_EL1 unless the active_mm == &init_mm, in which case
 106                  * the thread entered __cpu_suspend with TTBR0_EL1 set to
 107                  * reserved TTBR0 page tables and should be restored as such.
 108                  */
 109                 if (mm == &init_mm)
 110                         cpu_set_reserved_ttbr0();
 111                 else
 112                         cpu_switch_mm(mm->pgd, mm);
 113
 114                 flush_tlb_all();
 115
 116                 /*
 117                  * Restore per-cpu offset before any kernel
 118                  * subsystem relying on it has a chance to run.
 119                  */
 120                 set_my_cpu_offset(per_cpu_offset(smp_processor_id()));
 121
 122                 /*
 123                  * Restore HW breakpoint registers to sane values
 124                  * before debug exceptions are possibly reenabled
 125                  * through local_dbg_restore.
 126                  */
 127                 if (hw_breakpoint_restore)
 128                         hw_breakpoint_restore(NULL);
 129         }
 130
 131         /*
 132          * Restore pstate flags. OS lock and mdscr have been already
 133          * restored, so from this point onwards, debugging is fully
 134          * renabled if it was enabled when core started shutdown.
 135          */
 136         local_dbg_restore(flags);
 137
 138         return ret;
 139 }
 140
 141 struct sleep_save_sp sleep_save_sp;
 142 phys_addr_t sleep_idmap_phys;
 143
 144 static int __init cpu_suspend_init(void)
 145 {
 146         void *ctx_ptr;
 147
 148         /* ctx_ptr is an array of physical addresses */
 149         ctx_ptr = kcalloc(mpidr_hash_size(), sizeof(phys_addr_t), GFP_KERNEL);
 150
 151         if (WARN_ON(!ctx_ptr))
 152                 return -ENOMEM;
 153
 154         sleep_save_sp.save_ptr_stash = ctx_ptr;
 155         sleep_save_sp.save_ptr_stash_phys = virt_to_phys(ctx_ptr);
 156         sleep_idmap_phys = virt_to_phys(idmap_pg_dir);
 157         __flush_dcache_area(&sleep_save_sp, sizeof(struct sleep_save_sp));
 158         __flush_dcache_area(&sleep_idmap_phys, sizeof(sleep_idmap_phys));
 159
 160         return 0;
 161 }
 162 early_initcall(cpu_suspend_init);