arch/arm/common/mcpm_head.S

   1 /*
   2  * arch/arm/common/mcpm_head.S -- kernel entry point for multi-cluster PM
   3  *
   4  * Created by:  Nicolas Pitre, March 2012
   5  * Copyright:   (C) 2012-2013  Linaro Limited
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  *
  11  *
  12  * Refer to Documentation/arm/cluster-pm-race-avoidance.txt
  13  * for details of the synchronisation algorithms used here.
  14  */
  15
  16 #include <linux/linkage.h>
  17 #include <asm/mcpm.h>
  18 #include <asm/assembler.h>
  19
  20 #include "vlock.h"
  21
  22 .if MCPM_SYNC_CLUSTER_CPUS
  23 .error "cpus must be the first member of struct mcpm_sync_struct"
  24 .endif
  25
  26         .macro  pr_dbg  string
  27 #if defined(CONFIG_DEBUG_LL) && defined(DEBUG)
  28         b       1901f
  29 1902:   .asciz  "CPU"
  30 1903:   .asciz  " cluster"
  31 1904:   .asciz  ": \string"
  32         .align
  33 1901:   adr     r0, 1902b
  34         bl      printascii
  35         mov     r0, r9
  36         bl      printhex2
  37         adr     r0, 1903b
  38         bl      printascii
  39         mov     r0, r10
  40         bl      printhex2
  41         adr     r0, 1904b
  42         bl      printascii
  43 #endif
  44         .endm
  45
  46         .arm
  47         .align
  48
  49 ENTRY(mcpm_entry_point)
  50
  51  ARM_BE8(setend        be)
  52  THUMB( badr    r12, 1f         )
  53  THUMB( bx      r12             )
  54  THUMB( .thumb                  )
  55 1:
  56         mrc     p15, 0, r0, c0, c0, 5           @ MPIDR
  57         ubfx    r9, r0, #0, #8                  @ r9 = cpu
  58         ubfx    r10, r0, #8, #8                 @ r10 = cluster
  59         mov     r3, #MAX_CPUS_PER_CLUSTER
  60         mla     r4, r3, r10, r9                 @ r4 = canonical CPU index
  61         cmp     r4, #(MAX_CPUS_PER_CLUSTER * MAX_NR_CLUSTERS)
  62         blo     2f
  63
  64         /* We didn't expect this CPU.  Try to cheaply make it quiet. */
  65 1:      wfi
  66         wfe
  67         b       1b
  68
  69 2:      pr_dbg  "kernel mcpm_entry_point\n"
  70
  71         /*
  72          * MMU is off so we need to get to various variables in a
  73          * position independent way.
  74          */
  75         adr     r5, 3f
  76         ldmia   r5, {r0, r6, r7, r8, r11}
  77         add     r0, r5, r0                      @ r0 = mcpm_entry_early_pokes
  78         add     r6, r5, r6                      @ r6 = mcpm_entry_vectors
  79         ldr     r7, [r5, r7]                    @ r7 = mcpm_power_up_setup_phys
  80         add     r8, r5, r8                      @ r8 = mcpm_sync
  81         add     r11, r5, r11                    @ r11 = first_man_locks
  82
  83         @ Perform an early poke, if any
  84         add     r0, r0, r4, lsl #3
  85         ldmia   r0, {r0, r1}
  86         teq     r0, #0
  87         strne   r1, [r0]
  88
  89         mov     r0, #MCPM_SYNC_CLUSTER_SIZE
  90         mla     r8, r0, r10, r8                 @ r8 = sync cluster base
  91
  92         @ Signal that this CPU is coming UP:
  93         mov     r0, #CPU_COMING_UP
  94         mov     r5, #MCPM_SYNC_CPU_SIZE
  95         mla     r5, r9, r5, r8                  @ r5 = sync cpu address
  96         strb    r0, [r5]
  97
  98         @ At this point, the cluster cannot unexpectedly enter the GOING_DOWN
  99         @ state, because there is at least one active CPU (this CPU).
 100
 101         mov     r0, #VLOCK_SIZE
 102         mla     r11, r0, r10, r11               @ r11 = cluster first man lock
 103         mov     r0, r11
 104         mov     r1, r9                          @ cpu
 105         bl      vlock_trylock                   @ implies DMB
 106
 107         cmp     r0, #0                          @ failed to get the lock?
 108         bne     mcpm_setup_wait         @ wait for cluster setup if so
 109
 110         ldrb    r0, [r8, #MCPM_SYNC_CLUSTER_CLUSTER]
 111         cmp     r0, #CLUSTER_UP                 @ cluster already up?
 112         bne     mcpm_setup                      @ if not, set up the cluster
 113
 114         @ Otherwise, release the first man lock and skip setup:
 115         mov     r0, r11
 116         bl      vlock_unlock
 117         b       mcpm_setup_complete
 118
 119 mcpm_setup:
 120         @ Control dependency implies strb not observable before previous ldrb.
 121
 122         @ Signal that the cluster is being brought up:
 123         mov     r0, #INBOUND_COMING_UP
 124         strb    r0, [r8, #MCPM_SYNC_CLUSTER_INBOUND]
 125         dmb
 126
 127         @ Any CPU trying to take the cluster into CLUSTER_GOING_DOWN from this
 128         @ point onwards will observe INBOUND_COMING_UP and abort.
 129
 130         @ Wait for any previously-pending cluster teardown operations to abort
 131         @ or complete:
 132 mcpm_teardown_wait:
 133         ldrb    r0, [r8, #MCPM_SYNC_CLUSTER_CLUSTER]
 134         cmp     r0, #CLUSTER_GOING_DOWN
 135         bne     first_man_setup
 136         wfe
 137         b       mcpm_teardown_wait
 138
 139 first_man_setup:
 140         dmb
 141
 142         @ If the outbound gave up before teardown started, skip cluster setup:
 143
 144         cmp     r0, #CLUSTER_UP
 145         beq     mcpm_setup_leave
 146
 147         @ power_up_setup is now responsible for setting up the cluster:
 148
 149         cmp     r7, #0
 150         mov     r0, #1          @ second (cluster) affinity level
 151         blxne   r7              @ Call power_up_setup if defined
 152         dmb
 153
 154         mov     r0, #CLUSTER_UP
 155         strb    r0, [r8, #MCPM_SYNC_CLUSTER_CLUSTER]
 156         dmb
 157
 158 mcpm_setup_leave:
 159         @ Leave the cluster setup critical section:
 160
 161         mov     r0, #INBOUND_NOT_COMING_UP
 162         strb    r0, [r8, #MCPM_SYNC_CLUSTER_INBOUND]
 163         dsb     st
 164         sev
 165
 166         mov     r0, r11
 167         bl      vlock_unlock    @ implies DMB
 168         b       mcpm_setup_complete
 169
 170         @ In the contended case, non-first men wait here for cluster setup
 171         @ to complete:
 172 mcpm_setup_wait:
 173         ldrb    r0, [r8, #MCPM_SYNC_CLUSTER_CLUSTER]
 174         cmp     r0, #CLUSTER_UP
 175         wfene
 176         bne     mcpm_setup_wait
 177         dmb
 178
 179 mcpm_setup_complete:
 180         @ If a platform-specific CPU setup hook is needed, it is
 181         @ called from here.
 182
 183         cmp     r7, #0
 184         mov     r0, #0          @ first (CPU) affinity level
 185         blxne   r7              @ Call power_up_setup if defined
 186         dmb
 187
 188         @ Mark the CPU as up:
 189
 190         mov     r0, #CPU_UP
 191         strb    r0, [r5]
 192
 193         @ Observability order of CPU_UP and opening of the gate does not matter.
 194
 195 mcpm_entry_gated:
 196         ldr     r5, [r6, r4, lsl #2]            @ r5 = CPU entry vector
 197         cmp     r5, #0
 198         wfeeq
 199         beq     mcpm_entry_gated
 200         dmb
 201
 202         pr_dbg  "released\n"
 203         bx      r5
 204
 205         .align  2
 206
 207 3:      .word   mcpm_entry_early_pokes - .
 208         .word   mcpm_entry_vectors - 3b
 209         .word   mcpm_power_up_setup_phys - 3b
 210         .word   mcpm_sync - 3b
 211         .word   first_man_locks - 3b
 212
 213 ENDPROC(mcpm_entry_point)
 214
 215         .bss
 216
 217         .align  CACHE_WRITEBACK_ORDER
 218         .type   first_man_locks, #object
 219 first_man_locks:
 220         .space  VLOCK_SIZE * MAX_NR_CLUSTERS
 221         .align  CACHE_WRITEBACK_ORDER
 222
 223         .type   mcpm_entry_vectors, #object
 224 ENTRY(mcpm_entry_vectors)
 225         .space  4 * MAX_NR_CLUSTERS * MAX_CPUS_PER_CLUSTER
 226
 227         .type   mcpm_entry_early_pokes, #object
 228 ENTRY(mcpm_entry_early_pokes)
 229         .space  8 * MAX_NR_CLUSTERS * MAX_CPUS_PER_CLUSTER
 230
 231         .type   mcpm_power_up_setup_phys, #object
 232 ENTRY(mcpm_power_up_setup_phys)
 233         .space  4               @ set by mcpm_sync_init()