diff options
Diffstat (limited to 'arch/arm/common/mcpm_head.S')
| -rw-r--r-- | arch/arm/common/mcpm_head.S | 219 |
1 files changed, 219 insertions, 0 deletions
diff --git a/arch/arm/common/mcpm_head.S b/arch/arm/common/mcpm_head.S new file mode 100644 index 000000000000..8178705c4b24 --- /dev/null +++ b/arch/arm/common/mcpm_head.S @@ -0,0 +1,219 @@ +/* + * arch/arm/common/mcpm_head.S -- kernel entry point for multi-cluster PM + * + * Created by: Nicolas Pitre, March 2012 + * Copyright: (C) 2012-2013 Linaro Limited + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2 as + * published by the Free Software Foundation. + * + * + * Refer to Documentation/arm/cluster-pm-race-avoidance.txt + * for details of the synchronisation algorithms used here. + */ + +#include <linux/linkage.h> +#include <asm/mcpm.h> + +#include "vlock.h" + +.if MCPM_SYNC_CLUSTER_CPUS +.error "cpus must be the first member of struct mcpm_sync_struct" +.endif + + .macro pr_dbg string +#if defined(CONFIG_DEBUG_LL) && defined(DEBUG) + b 1901f +1902: .asciz "CPU" +1903: .asciz " cluster" +1904: .asciz ": \string" + .align +1901: adr r0, 1902b + bl printascii + mov r0, r9 + bl printhex8 + adr r0, 1903b + bl printascii + mov r0, r10 + bl printhex8 + adr r0, 1904b + bl printascii +#endif + .endm + + .arm + .align + +ENTRY(mcpm_entry_point) + + THUMB( adr r12, BSYM(1f) ) + THUMB( bx r12 ) + THUMB( .thumb ) +1: + mrc p15, 0, r0, c0, c0, 5 @ MPIDR + ubfx r9, r0, #0, #8 @ r9 = cpu + ubfx r10, r0, #8, #8 @ r10 = cluster + mov r3, #MAX_CPUS_PER_CLUSTER + mla r4, r3, r10, r9 @ r4 = canonical CPU index + cmp r4, #(MAX_CPUS_PER_CLUSTER * MAX_NR_CLUSTERS) + blo 2f + + /* We didn't expect this CPU. Try to cheaply make it quiet. */ +1: wfi + wfe + b 1b + +2: pr_dbg "kernel mcpm_entry_point\n" + + /* + * MMU is off so we need to get to various variables in a + * position independent way. + */ + adr r5, 3f + ldmia r5, {r6, r7, r8, r11} + add r6, r5, r6 @ r6 = mcpm_entry_vectors + ldr r7, [r5, r7] @ r7 = mcpm_power_up_setup_phys + add r8, r5, r8 @ r8 = mcpm_sync + add r11, r5, r11 @ r11 = first_man_locks + + mov r0, #MCPM_SYNC_CLUSTER_SIZE + mla r8, r0, r10, r8 @ r8 = sync cluster base + + @ Signal that this CPU is coming UP: + mov r0, #CPU_COMING_UP + mov r5, #MCPM_SYNC_CPU_SIZE + mla r5, r9, r5, r8 @ r5 = sync cpu address + strb r0, [r5] + + @ At this point, the cluster cannot unexpectedly enter the GOING_DOWN + @ state, because there is at least one active CPU (this CPU). + + mov r0, #VLOCK_SIZE + mla r11, r0, r10, r11 @ r11 = cluster first man lock + mov r0, r11 + mov r1, r9 @ cpu + bl vlock_trylock @ implies DMB + + cmp r0, #0 @ failed to get the lock? + bne mcpm_setup_wait @ wait for cluster setup if so + + ldrb r0, [r8, #MCPM_SYNC_CLUSTER_CLUSTER] + cmp r0, #CLUSTER_UP @ cluster already up? + bne mcpm_setup @ if not, set up the cluster + + @ Otherwise, release the first man lock and skip setup: + mov r0, r11 + bl vlock_unlock + b mcpm_setup_complete + +mcpm_setup: + @ Control dependency implies strb not observable before previous ldrb. + + @ Signal that the cluster is being brought up: + mov r0, #INBOUND_COMING_UP + strb r0, [r8, #MCPM_SYNC_CLUSTER_INBOUND] + dmb + + @ Any CPU trying to take the cluster into CLUSTER_GOING_DOWN from this + @ point onwards will observe INBOUND_COMING_UP and abort. + + @ Wait for any previously-pending cluster teardown operations to abort + @ or complete: +mcpm_teardown_wait: + ldrb r0, [r8, #MCPM_SYNC_CLUSTER_CLUSTER] + cmp r0, #CLUSTER_GOING_DOWN + bne first_man_setup + wfe + b mcpm_teardown_wait + +first_man_setup: + dmb + + @ If the outbound gave up before teardown started, skip cluster setup: + + cmp r0, #CLUSTER_UP + beq mcpm_setup_leave + + @ power_up_setup is now responsible for setting up the cluster: + + cmp r7, #0 + mov r0, #1 @ second (cluster) affinity level + blxne r7 @ Call power_up_setup if defined + dmb + + mov r0, #CLUSTER_UP + strb r0, [r8, #MCPM_SYNC_CLUSTER_CLUSTER] + dmb + +mcpm_setup_leave: + @ Leave the cluster setup critical section: + + mov r0, #INBOUND_NOT_COMING_UP + strb r0, [r8, #MCPM_SYNC_CLUSTER_INBOUND] + dsb + sev + + mov r0, r11 + bl vlock_unlock @ implies DMB + b mcpm_setup_complete + + @ In the contended case, non-first men wait here for cluster setup + @ to complete: +mcpm_setup_wait: + ldrb r0, [r8, #MCPM_SYNC_CLUSTER_CLUSTER] + cmp r0, #CLUSTER_UP + wfene + bne mcpm_setup_wait + dmb + +mcpm_setup_complete: + @ If a platform-specific CPU setup hook is needed, it is + @ called from here. + + cmp r7, #0 + mov r0, #0 @ first (CPU) affinity level + blxne r7 @ Call power_up_setup if defined + dmb + + @ Mark the CPU as up: + + mov r0, #CPU_UP + strb r0, [r5] + + @ Observability order of CPU_UP and opening of the gate does not matter. + +mcpm_entry_gated: + ldr r5, [r6, r4, lsl #2] @ r5 = CPU entry vector + cmp r5, #0 + wfeeq + beq mcpm_entry_gated + dmb + + pr_dbg "released\n" + bx r5 + + .align 2 + +3: .word mcpm_entry_vectors - . + .word mcpm_power_up_setup_phys - 3b + .word mcpm_sync - 3b + .word first_man_locks - 3b + +ENDPROC(mcpm_entry_point) + + .bss + + .align CACHE_WRITEBACK_ORDER + .type first_man_locks, #object +first_man_locks: + .space VLOCK_SIZE * MAX_NR_CLUSTERS + .align CACHE_WRITEBACK_ORDER + + .type mcpm_entry_vectors, #object +ENTRY(mcpm_entry_vectors) + .space 4 * MAX_NR_CLUSTERS * MAX_CPUS_PER_CLUSTER + + .type mcpm_power_up_setup_phys, #object +ENTRY(mcpm_power_up_setup_phys) + .space 4 @ set by mcpm_sync_init() |