LXR linux/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
  13extern 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 */
  23void 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 */
  45static void (*hw_breakpoint_restore)(void *);
  46void __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 */
  61int 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
 122struct sleep_save_sp sleep_save_sp;
 123
 124static 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}
 140early_initcall(cpu_suspend_init);
 141