arch/arm/include/asm/percpu.h

   1 /* SPDX-License-Identifier: GPL-2.0-only */
   2 /*
   3  * Copyright 2012 Calxeda, Inc.
   4  */
   5 #ifndef _ASM_ARM_PERCPU_H_
   6 #define _ASM_ARM_PERCPU_H_
   7
   8 #include <asm/insn.h>
   9
  10 register unsigned long current_stack_pointer asm ("sp");
  11
  12 /*
  13  * Same as asm-generic/percpu.h, except that we store the per cpu offset
  14  * in the TPIDRPRW. TPIDRPRW only exists on V6K and V7
  15  */
  16 #ifdef CONFIG_SMP
  17 static inline void set_my_cpu_offset(unsigned long off)
  18 {
  19         extern unsigned int smp_on_up;
  20
  21         if (IS_ENABLED(CONFIG_CPU_V6) && !smp_on_up)
  22                 return;
  23
  24         /* Set TPIDRPRW */
  25         asm volatile("mcr p15, 0, %0, c13, c0, 4" : : "r" (off) : "memory");
  26 }
  27
  28 static __always_inline unsigned long __my_cpu_offset(void)
  29 {
  30         unsigned long off;
  31
  32         /*
  33          * Read TPIDRPRW.
  34          * We want to allow caching the value, so avoid using volatile and
  35          * instead use a fake stack read to hazard against barrier().
  36          */
  37         asm("0: mrc p15, 0, %0, c13, c0, 4                      \n\t"
  38 #ifdef CONFIG_CPU_V6
  39             "1:                                                 \n\t"
  40             "   .subsection 1                                   \n\t"
  41 #if defined(CONFIG_ARM_HAS_GROUP_RELOCS) && \
  42     !(defined(MODULE) && defined(CONFIG_ARM_MODULE_PLTS))
  43             "2: " LOAD_SYM_ARMV6(%0, __per_cpu_offset) "        \n\t"
  44             "   b       1b                                      \n\t"
  45 #else
  46             "2: ldr     %0, 3f                                  \n\t"
  47             "   ldr     %0, [%0]                                \n\t"
  48             "   b       1b                                      \n\t"
  49             "3: .long   __per_cpu_offset                        \n\t"
  50 #endif
  51             "   .previous                                       \n\t"
  52             "   .pushsection \".alt.smp.init\", \"a\"           \n\t"
  53             "   .long   0b - .                                  \n\t"
  54             "   b       . + (2b - 0b)                           \n\t"
  55             "   .popsection                                     \n\t"
  56 #endif
  57              : "=r" (off)
  58              : "Q" (*(const unsigned long *)current_stack_pointer));
  59
  60         return off;
  61 }
  62 #define __my_cpu_offset __my_cpu_offset()
  63 #else
  64 #define set_my_cpu_offset(x)    do {} while(0)
  65
  66 #endif /* CONFIG_SMP */
  67
  68 #include <asm-generic/percpu.h>
  69
  70 #endif /* _ASM_ARM_PERCPU_H_ */