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 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 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 /*
  55  * cpu_suspend
  56  *
  57  * arg: argument to pass to the finisher function
  58  * fn: finisher function pointer
  59  *
  60  */
  61 int cpu_suspend(unsigned long arg, int (*fn)(unsigned long))
  62 {
  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          * Function graph tracer state gets incosistent when the kernel
  75          * calls functions that never return (aka suspend finishers) hence
  76          * disable graph tracing during their execution.
  77          */
  78         pause_graph_tracing();
  79
  80         /*
  81          * mm context saved on the stack, it will be restored when
  82          * the cpu comes out of reset through the identity mapped
  83          * page tables, so that the thread address space is properly
  84          * set-up on function return.
  85          */
  86         ret = __cpu_suspend_enter(arg, fn);
  87         if (ret == 0) {
  88                 /*
  89                  * We are resuming from reset with the idmap active in TTBR0_EL1.
  90                  * We must uninstall the idmap and restore the expected MMU
  91                  * state before we can possibly return to userspace.
  92                  */
  93                 cpu_uninstall_idmap();
  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         unpause_graph_tracing();
 111
 112         /*
 113          * Restore pstate flags. OS lock and mdscr have been already
 114          * restored, so from this point onwards, debugging is fully
 115          * renabled if it was enabled when core started shutdown.
 116          */
 117         local_dbg_restore(flags);
 118
 119         return ret;
 120 }
 121
 122 struct sleep_save_sp sleep_save_sp;
 123
 124 static int __init cpu_suspend_init(void)
 125 {
 126         void *ctx_ptr;
 127
 128         /* ctx_ptr is an array of physical addresses */
 129         ctx_ptr = kcalloc(mpidr_hash_size(), sizeof(phys_addr_t), GFP_KERNEL);
 130
 131         if (WARN_ON(!ctx_ptr))
 132                 return -ENOMEM;
 133
 134         sleep_save_sp.save_ptr_stash = ctx_ptr;
 135         sleep_save_sp.save_ptr_stash_phys = virt_to_phys(ctx_ptr);
 136         __flush_dcache_area(&sleep_save_sp, sizeof(struct sleep_save_sp));
 137
 138         return 0;
 139 }
 140 early_initcall(cpu_suspend_init);