diff options
| -rw-r--r-- | Documentation/arm/cluster-pm-race-avoidance.txt | 498 | ||||
| -rw-r--r-- | arch/arm/common/mcpm_entry.c | 150 | ||||
| -rw-r--r-- | arch/arm/common/mcpm_head.S | 106 | ||||
| -rw-r--r-- | arch/arm/include/asm/mcpm.h | 73 | ||||
| -rw-r--r-- | arch/arm/kernel/asm-offsets.c | 3 |
5 files changed, 828 insertions, 2 deletions
diff --git a/Documentation/arm/cluster-pm-race-avoidance.txt b/Documentation/arm/cluster-pm-race-avoidance.txt new file mode 100644 index 00000000000..750b6fc24af --- /dev/null +++ b/Documentation/arm/cluster-pm-race-avoidance.txt @@ -0,0 +1,498 @@ +Cluster-wide Power-up/power-down race avoidance algorithm +========================================================= + +This file documents the algorithm which is used to coordinate CPU and +cluster setup and teardown operations and to manage hardware coherency +controls safely. + +The section "Rationale" explains what the algorithm is for and why it is +needed. "Basic model" explains general concepts using a simplified view +of the system. The other sections explain the actual details of the +algorithm in use. + + +Rationale +--------- + +In a system containing multiple CPUs, it is desirable to have the +ability to turn off individual CPUs when the system is idle, reducing +power consumption and thermal dissipation. + +In a system containing multiple clusters of CPUs, it is also desirable +to have the ability to turn off entire clusters. + +Turning entire clusters off and on is a risky business, because it +involves performing potentially destructive operations affecting a group +of independently running CPUs, while the OS continues to run. This +means that we need some coordination in order to ensure that critical +cluster-level operations are only performed when it is truly safe to do +so. + +Simple locking may not be sufficient to solve this problem, because +mechanisms like Linux spinlocks may rely on coherency mechanisms which +are not immediately enabled when a cluster powers up. Since enabling or +disabling those mechanisms may itself be a non-atomic operation (such as +writing some hardware registers and invalidating large caches), other +methods of coordination are required in order to guarantee safe +power-down and power-up at the cluster level. + +The mechanism presented in this document describes a coherent memory +based protocol for performing the needed coordination. It aims to be as +lightweight as possible, while providing the required safety properties. + + +Basic model +----------- + +Each cluster and CPU is assigned a state, as follows: + + DOWN + COMING_UP + UP + GOING_DOWN + + +---------> UP ----------+ + | v + + COMING_UP GOING_DOWN + + ^ | + +--------- DOWN <--------+ + + +DOWN: The CPU or cluster is not coherent, and is either powered off or + suspended, or is ready to be powered off or suspended. + +COMING_UP: The CPU or cluster has committed to moving to the UP state. + It may be part way through the process of initialisation and + enabling coherency. + +UP: The CPU or cluster is active and coherent at the hardware + level. A CPU in this state is not necessarily being used + actively by the kernel. + +GOING_DOWN: The CPU or cluster has committed to moving to the DOWN + state. It may be part way through the process of teardown and + coherency exit. + + +Each CPU has one of these states assigned to it at any point in time. +The CPU states are described in the "CPU state" section, below. + +Each cluster is also assigned a state, but it is necessary to split the +state value into two parts (the "cluster" state and "inbound" state) and +to introduce additional states in order to avoid races between different +CPUs in the cluster simultaneously modifying the state. The cluster- +level states are described in the "Cluster state" section. + +To help distinguish the CPU states from cluster states in this +discussion, the state names are given a CPU_ prefix for the CPU states, +and a CLUSTER_ or INBOUND_ prefix for the cluster states. + + +CPU state +--------- + +In this algorithm, each individual core in a multi-core processor is +referred to as a "CPU". CPUs are assumed to be single-threaded: +therefore, a CPU can only be doing one thing at a single point in time. + +This means that CPUs fit the basic model closely. + +The algorithm defines the following states for each CPU in the system: + + CPU_DOWN + CPU_COMING_UP + CPU_UP + CPU_GOING_DOWN + + cluster setup and + CPU setup complete policy decision + +-----------> CPU_UP ------------+ + | v + + CPU_COMING_UP CPU_GOING_DOWN + + ^ | + +----------- CPU_DOWN <----------+ + policy decision CPU teardown complete + or hardware event + + +The definitions of the four states correspond closely to the states of +the basic model. + +Transitions between states occur as follows. + +A trigger event (spontaneous) means that the CPU can transition to the +next state as a result of making local progress only, with no +requirement for any external event to happen. + + +CPU_DOWN: + + A CPU reaches the CPU_DOWN state when it is ready for + power-down. On reaching this state, the CPU will typically + power itself down or suspend itself, via a WFI instruction or a + firmware call. + + Next state: CPU_COMING_UP + Conditions: none + + Trigger events: + + a) an explicit hardware power-up operation, resulting + from a policy decision on another CPU; + + b) a hardware event, such as an interrupt. + + +CPU_COMING_UP: + + A CPU cannot start participating in hardware coherency until the + cluster is set up and coherent. If the cluster is not ready, + then the CPU will wait in the CPU_COMING_UP state until the + cluster has been set up. + + Next state: CPU_UP + Conditions: The CPU's parent cluster must be in CLUSTER_UP. + Trigger events: Transition of the parent cluster to CLUSTER_UP. + + Refer to the "Cluster state" section for a description of the + CLUSTER_UP state. + + +CPU_UP: + When a CPU reaches the CPU_UP state, it is safe for the CPU to + start participating in local coherency. + + This is done by jumping to the kernel's CPU resume code. + + Note that the definition of this state is slightly different + from the basic model definition: CPU_UP does not mean that the + CPU is coherent yet, but it does mean that it is safe to resume + the kernel. The kernel handles the rest of the resume + procedure, so the remaining steps are not visible as part of the + race avoidance algorithm. + + The CPU remains in this state until an explicit policy decision + is made to shut down or suspend the CPU. + + Next state: CPU_GOING_DOWN + Conditions: none + Trigger events: explicit policy decision + + +CPU_GOING_DOWN: + + While in this state, the CPU exits coherency, including any + operations required to achieve this (such as cleaning data + caches). + + Next state: CPU_DOWN + Conditions: local CPU teardown complete + Trigger events: (spontaneous) + + +Cluster state +------------- + +A cluster is a group of connected CPUs with some common resources. +Because a cluster contains multiple CPUs, it can be doing multiple +things at the same time. This has some implications. In particular, a +CPU can start up while another CPU is tearing the cluster down. + +In this discussion, the "outbound side" is the view of the cluster state +as seen by a CPU tearing the cluster down. The "inbound side" is the +view of the cluster state as seen by a CPU setting the CPU up. + +In order to enable safe coordination in such situations, it is important +that a CPU which is setting up the cluster can advertise its state +independently of the CPU which is tearing down the cluster. For this +reason, the cluster state is split into two parts: + + "cluster" state: The global state of the cluster; or the state + on the outbound side: + + CLUSTER_DOWN + CLUSTER_UP + CLUSTER_GOING_DOWN + + "inbound" state: The state of the cluster on the inbound side. + + INBOUND_NOT_COMING_UP + INBOUND_COMING_UP + + + The different pairings of these states results in six possible + states for the cluster as a whole: + + CLUSTER_UP + +==========> INBOUND_NOT_COMING_UP -------------+ + # | + | + CLUSTER_UP <----+ | + INBOUND_COMING_UP | v + + ^ CLUSTER_GOING_DOWN CLUSTER_GOING_DOWN + # INBOUND_COMING_UP <=== INBOUND_NOT_COMING_UP + + CLUSTER_DOWN | | + INBOUND_COMING_UP <----+ | + | + ^ | + +=========== CLUSTER_DOWN <------------+ + INBOUND_NOT_COMING_UP + + Transitions -----> can only be made by the outbound CPU, and + only involve changes to the "cluster" state. + + Transitions ===##> can only be made by the inbound CPU, and only + involve changes to the "inbound" state, except where there is no + further transition possible on the outbound side (i.e., the + outbound CPU has put the cluster into the CLUSTER_DOWN state). + + The race avoidance algorithm does not provide a way to determine + which exact CPUs within the cluster play these roles. This must + be decided in advance by some other means. Refer to the section + "Last man and first man selection" for more explanation. + + + CLUSTER_DOWN/INBOUND_NOT_COMING_UP is the only state where the + cluster can actually be powered down. + + The parallelism of the inbound and outbound CPUs is observed by + the existence of two different paths from CLUSTER_GOING_DOWN/ + INBOUND_NOT_COMING_UP (corresponding to GOING_DOWN in the basic + model) to CLUSTER_DOWN/INBOUND_COMING_UP (corresponding to + COMING_UP in the basic model). The second path avoids cluster + teardown completely. + + CLUSTER_UP/INBOUND_COMING_UP is equivalent to UP in the basic + model. The final transition to CLUSTER_UP/INBOUND_NOT_COMING_UP + is trivial and merely resets the state machine ready for the + next cycle. + + Details of the allowable transitions follow. + + The next state in each case is notated + + <cluster state>/<inbound state> (<transitioner>) + + where the <transitioner> is the side on which the transition + can occur; either the inbound or the outbound side. + + +CLUSTER_DOWN/INBOUND_NOT_COMING_UP: + + Next state: CLUSTER_DOWN/INBOUND_COMING_UP (inbound) + Conditions: none + Trigger events: + + a) an explicit hardware power-up operation, resulting + from a policy decision on another CPU; + + b) a hardware event, such as an interrupt. + + +CLUSTER_DOWN/INBOUND_COMING_UP: + + In this state, an inbound CPU sets up the cluster, including + enabling of hardware coherency at the cluster level and any + other operations (such as cache invalidation) which are required + in order to achieve this. + + The purpose of this state is to do sufficient cluster-level + setup to enable other CPUs in the cluster to enter coherency + safely. + + Next state: CLUSTER_UP/INBOUND_COMING_UP (inbound) + Conditions: cluster-level setup and hardware coherency complete + Trigger events: (spontaneous) + + +CLUSTER_UP/INBOUND_COMING_UP: + + Cluster-level setup is complete and hardware coherency is + enabled for the cluster. Other CPUs in the cluster can safely + enter coherency. + + This is a transient state, leading immediately to + CLUSTER_UP/INBOUND_NOT_COMING_UP. All other CPUs on the cluster + should consider treat these two states as equivalent. + + Next state: CLUSTER_UP/INBOUND_NOT_COMING_UP (inbound) + Conditions: none + Trigger events: (spontaneous) + + +CLUSTER_UP/INBOUND_NOT_COMING_UP: + + Cluster-level setup is complete and hardware coherency is + enabled for the cluster. Other CPUs in the cluster can safely + enter coherency. + + The cluster will remain in this state until a policy decision is + made to power the cluster down. + + Next state: CLUSTER_GOING_DOWN/INBOUND_NOT_COMING_UP (outbound) + Conditions: none + Trigger events: policy decision to power down the cluster + + +CLUSTER_GOING_DOWN/INBOUND_NOT_COMING_UP: + + An outbound CPU is tearing the cluster down. The selected CPU + must wait in this state until all CPUs in the cluster are in the + CPU_DOWN state. + + When all CPUs are in the CPU_DOWN state, the cluster can be torn + down, for example by cleaning data caches and exiting + cluster-level coherency. + + To avoid wasteful unnecessary teardown operations, the outbound + should check the inbound cluster state for asynchronous + transitions to INBOUND_COMING_UP. Alternatively, individual + CPUs can be checked for entry into CPU_COMING_UP or CPU_UP. + + + Next states: + + CLUSTER_DOWN/INBOUND_NOT_COMING_UP (outbound) + Conditions: cluster torn down and ready to power off + Trigger events: (spontaneous) + + CLUSTER_GOING_DOWN/INBOUND_COMING_UP (inbound) + Conditions: none + Trigger events: + + a) an explicit hardware power-up operation, + resulting from a policy decision on another + CPU; + + b) a hardware event, such as an interrupt. + + +CLUSTER_GOING_DOWN/INBOUND_COMING_UP: + + The cluster is (or was) being torn down, but another CPU has + come online in the meantime and is trying to set up the cluster + again. + + If the outbound CPU observes this state, it has two choices: + + a) back out of teardown, restoring the cluster to the + CLUSTER_UP state; + + b) finish tearing the cluster down and put the cluster + in the CLUSTER_DOWN state; the inbound CPU will + set up the cluster again from there. + + Choice (a) permits the removal of some latency by avoiding + unnecessary teardown and setup operations in situations where + the cluster is not really going to be powered down. + + + Next states: + + CLUSTER_UP/INBOUND_COMING_UP (outbound) + Conditions: cluster-level setup and hardware + coherency complete + Trigger events: (spontaneous) + + CLUSTER_DOWN/INBOUND_COMING_UP (outbound) + Conditions: cluster torn down and ready to power off + Trigger events: (spontaneous) + + +Last man and First man selection +-------------------------------- + +The CPU which performs cluster tear-down operations on the outbound side +is commonly referred to as the "last man". + +The CPU which performs cluster setup on the inbound side is commonly +referred to as the "first man". + +The race avoidance algorithm documented above does not provide a +mechanism to choose which CPUs should play these roles. + + +Last man: + +When shutting down the cluster, all the CPUs involved are initially +executing Linux and hence coherent. Therefore, ordinary spinlocks can +be used to select a last man safely, before the CPUs become +non-coherent. + + +First man: + +Because CPUs may power up asynchronously in response to external wake-up +events, a dynamic mechanism is needed to make sure that only one CPU +attempts to play the first man role and do the cluster-level +initialisation: any other CPUs must wait for this to complete before +proceeding. + +Cluster-level initialisation may involve actions such as configuring +coherency controls in the bus fabric. + +The current implementation in mcpm_head.S uses a separate mutual exclusion +mechanism to do this arbitration. This mechanism is documented in +detail in vlocks.txt. + + +Features and Limitations +------------------------ + +Implementation: + + The current ARM-based implementation is split between + arch/arm/common/mcpm_head.S (low-level inbound CPU operations) and + arch/arm/common/mcpm_entry.c (everything else): + + __mcpm_cpu_going_down() signals the transition of a CPU to the + CPU_GOING_DOWN state. + + __mcpm_cpu_down() signals the transition of a CPU to the CPU_DOWN + state. + + A CPU transitions to CPU_COMING_UP and then to CPU_UP via the + low-level power-up code in mcpm_head.S. This could + involve CPU-specific setup code, but in the current + implementation it does not. + + __mcpm_outbound_enter_critical() and __mcpm_outbound_leave_critical() + handle transitions from CLUSTER_UP to CLUSTER_GOING_DOWN + and from there to CLUSTER_DOWN or back to CLUSTER_UP (in + the case of an aborted cluster power-down). + + These functions are more complex than the __mcpm_cpu_*() + functions due to the extra inter-CPU coordination which + is needed for safe transitions at the cluster level. + + A cluster transitions from CLUSTER_DOWN back to CLUSTER_UP via + the low-level power-up code in mcpm_head.S. This + typically involves platform-specific setup code, + provided by the platform-specific power_up_setup + function registered via mcpm_sync_init. + +Deep topologies: + + As currently described and implemented, the algorithm does not + support CPU topologies involving more than two levels (i.e., + clusters of clusters are not supported). The algorithm could be + extended by replicating the cluster-level states for the + additional topological levels, and modifying the transition + rules for the intermediate (non-outermost) cluster levels. + + +Colophon +-------- + +Originally created and documented by Dave Martin for Linaro Limited, in +collaboration with Nicolas Pitre and Achin Gupta. + +Copyright (C) 2012-2013 Linaro Limited +Distributed under the terms of Version 2 of the GNU General Public +License, as defined in linux/COPYING. diff --git a/arch/arm/common/mcpm_entry.c b/arch/arm/common/mcpm_entry.c index 5d72889a58a..370236dd1a0 100644 --- a/arch/arm/common/mcpm_entry.c +++ b/arch/arm/common/mcpm_entry.c @@ -16,6 +16,7 @@ #include <asm/mcpm.h> #include <asm/cacheflush.h> #include <asm/idmap.h> +#include <asm/cputype.h> extern unsigned long mcpm_entry_vectors[MAX_NR_CLUSTERS][MAX_CPUS_PER_CLUSTER]; @@ -111,3 +112,152 @@ int mcpm_cpu_powered_up(void) platform_ops->powered_up(); return 0; } + +struct sync_struct mcpm_sync; + +/* + * __mcpm_cpu_going_down: Indicates that the cpu is being torn down. + * This must be called at the point of committing to teardown of a CPU. + * The CPU cache (SCTRL.C bit) is expected to still be active. + */ +void __mcpm_cpu_going_down(unsigned int cpu, unsigned int cluster) +{ + mcpm_sync.clusters[cluster].cpus[cpu].cpu = CPU_GOING_DOWN; + sync_cache_w(&mcpm_sync.clusters[cluster].cpus[cpu].cpu); +} + +/* + * __mcpm_cpu_down: Indicates that cpu teardown is complete and that the + * cluster can be torn down without disrupting this CPU. + * To avoid deadlocks, this must be called before a CPU is powered down. + * The CPU cache (SCTRL.C bit) is expected to be off. + * However L2 cache might or might not be active. + */ +void __mcpm_cpu_down(unsigned int cpu, unsigned int cluster) +{ + dmb(); + mcpm_sync.clusters[cluster].cpus[cpu].cpu = CPU_DOWN; + sync_cache_w(&mcpm_sync.clusters[cluster].cpus[cpu].cpu); + dsb_sev(); +} + +/* + * __mcpm_outbound_leave_critical: Leave the cluster teardown critical section. + * @state: the final state of the cluster: + * CLUSTER_UP: no destructive teardown was done and the cluster has been + * restored to the previous state (CPU cache still active); or + * CLUSTER_DOWN: the cluster has been torn-down, ready for power-off + * (CPU cache disabled, L2 cache either enabled or disabled). + */ +void __mcpm_outbound_leave_critical(unsigned int cluster, int state) +{ + dmb(); + mcpm_sync.clusters[cluster].cluster = state; + sync_cache_w(&mcpm_sync.clusters[cluster].cluster); + dsb_sev(); +} + +/* + * __mcpm_outbound_enter_critical: Enter the cluster teardown critical section. + * This function should be called by the last man, after local CPU teardown + * is complete. CPU cache expected to be active. + * + * Returns: + * false: the critical section was not entered because an inbound CPU was + * observed, or the cluster is already being set up; + * true: the critical section was entered: it is now safe to tear down the + * cluster. + */ +bool __mcpm_outbound_enter_critical(unsigned int cpu, unsigned int cluster) +{ + unsigned int i; + struct mcpm_sync_struct *c = &mcpm_sync.clusters[cluster]; + + /* Warn inbound CPUs that the cluster is being torn down: */ + c->cluster = CLUSTER_GOING_DOWN; + sync_cache_w(&c->cluster); + + /* Back out if the inbound cluster is already in the critical region: */ + sync_cache_r(&c->inbound); + if (c->inbound == INBOUND_COMING_UP) + goto abort; + + /* + * Wait for all CPUs to get out of the GOING_DOWN state, so that local + * teardown is complete on each CPU before tearing down the cluster. + * + * If any CPU has been woken up again from the DOWN state, then we + * shouldn't be taking the cluster down at all: abort in that case. + */ + sync_cache_r(&c->cpus); + for (i = 0; i < MAX_CPUS_PER_CLUSTER; i++) { + int cpustate; + + if (i == cpu) + continue; + + while (1) { + cpustate = c->cpus[i].cpu; + if (cpustate != CPU_GOING_DOWN) + break; + + wfe(); + sync_cache_r(&c->cpus[i].cpu); + } + + switch (cpustate) { + case CPU_DOWN: + continue; + + default: + goto abort; + } + } + + return true; + +abort: + __mcpm_outbound_leave_critical(cluster, CLUSTER_UP); + return false; +} + +int __mcpm_cluster_state(unsigned int cluster) +{ + sync_cache_r(&mcpm_sync.clusters[cluster].cluster); + return mcpm_sync.clusters[cluster].cluster; +} + +extern unsigned long mcpm_power_up_setup_phys; + +int __init mcpm_sync_init( + void (*power_up_setup)(unsigned int affinity_level)) +{ + unsigned int i, j, mpidr, this_cluster; + + BUILD_BUG_ON(MCPM_SYNC_CLUSTER_SIZE * MAX_NR_CLUSTERS != sizeof mcpm_sync); + BUG_ON((unsigned long)&mcpm_sync & (__CACHE_WRITEBACK_GRANULE - 1)); + + /* + * Set initial CPU and cluster states. + * Only one cluster is assumed to be active at this point. + */ + for (i = 0; i < MAX_NR_CLUSTERS; i++) { + mcpm_sync.clusters[i].cluster = CLUSTER_DOWN; + mcpm_sync.clusters[i].inbound = INBOUND_NOT_COMING_UP; + for (j = 0; j < MAX_CPUS_PER_CLUSTER; j++) + mcpm_sync.clusters[i].cpus[j].cpu = CPU_DOWN; + } + mpidr = read_cpuid_mpidr(); + this_cluster = MPIDR_AFFINITY_LEVEL(mpidr, 1); + for_each_online_cpu(i) + mcpm_sync.clusters[this_cluster].cpus[i].cpu = CPU_UP; + mcpm_sync.clusters[this_cluster].cluster = CLUSTER_UP; + sync_cache_w(&mcpm_sync); + + if (power_up_setup) { + mcpm_power_up_setup_phys = virt_to_phys(power_up_setup); + sync_cache_w(&mcpm_power_up_setup_phys); + } + + return 0; +} diff --git a/arch/arm/common/mcpm_head.S b/arch/arm/common/mcpm_head.S index 68c9903075a..7d729bd7267 100644 --- a/arch/arm/common/mcpm_head.S +++ b/arch/arm/common/mcpm_head.S @@ -7,11 +7,19 @@ * 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> +.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 @@ -57,24 +65,114 @@ ENTRY(mcpm_entry_point) 2: pr_dbg "kernel mcpm_entry_point\n" /* - * MMU is off so we need to get to mcpm_entry_vectors in a + * MMU is off so we need to get to various variables in a * position independent way. */ adr r5, 3f - ldr r6, [r5] + ldmia r5, {r6, r7, r8} 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 + + 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). + + @ Note: the following is racy as another CPU might be testing + @ the same flag at the same moment. That'll be fixed later. + ldrb r0, [r8, #MCPM_SYNC_CLUSTER_CLUSTER] + cmp r0, #CLUSTER_UP @ cluster already up? + bne mcpm_setup @ if not, set up the cluster + + @ Otherwise, skip setup: + 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 + +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 ENDPROC(mcpm_entry_point) @@ -84,3 +182,7 @@ ENDPROC(mcpm_entry_point) .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() diff --git a/arch/arm/include/asm/mcpm.h b/arch/arm/include/asm/mcpm.h index 627761fce78..3046e90210c 100644 --- a/arch/arm/include/asm/mcpm.h +++ b/arch/arm/include/asm/mcpm.h @@ -24,6 +24,9 @@ #ifndef __ASSEMBLY__ +#include <linux/types.h> +#include <asm/cacheflush.h> + /* * Platform specific code should use this symbol to set up secondary * entry location for processors to use when released from reset. @@ -130,5 +133,75 @@ struct mcpm_platform_ops { */ int __init mcpm_platform_register(const struct mcpm_platform_ops *ops); +/* Synchronisation structures for coordinating safe cluster setup/teardown: */ + +/* + * When modifying this structure, make sure you update the MCPM_SYNC_ defines + * to match. + */ +struct mcpm_sync_struct { + /* individual CPU states */ + struct { + s8 cpu __aligned(__CACHE_WRITEBACK_GRANULE); + } cpus[MAX_CPUS_PER_CLUSTER]; + + /* cluster state */ + s8 cluster __aligned(__CACHE_WRITEBACK_GRANULE); + + /* inbound-side state */ + s8 inbound __aligned(__CACHE_WRITEBACK_GRANULE); +}; + +struct sync_struct { + struct mcpm_sync_struct clusters[MAX_NR_CLUSTERS]; +}; + +extern unsigned long sync_phys; /* physical address of *mcpm_sync */ + +void __mcpm_cpu_going_down(unsigned int cpu, unsigned int cluster); +void __mcpm_cpu_down(unsigned int cpu, unsigned int cluster); +void __mcpm_outbound_leave_critical(unsigned int cluster, int state); +bool __mcpm_outbound_enter_critical(unsigned int this_cpu, unsigned int cluster); +int __mcpm_cluster_state(unsigned int cluster); + +int __init mcpm_sync_init( + void (*power_up_setup)(unsigned int affinity_level)); + +#else + +/* + * asm-offsets.h causes trouble when included in .c files, and cacheflush.h + * cannot be included in asm files. Let's work around the conflict like this. + */ +#include <asm/asm-offsets.h> +#define __CACHE_WRITEBACK_GRANULE CACHE_WRITEBACK_GRANULE + #endif /* ! __ASSEMBLY__ */ + +/* Definitions for mcpm_sync_struct */ +#define CPU_DOWN 0x11 +#define CPU_COMING_UP 0x12 +#define CPU_UP 0x13 +#define CPU_GOING_DOWN 0x14 + +#define CLUSTER_DOWN 0x21 +#define CLUSTER_UP 0x22 +#define CLUSTER_GOING_DOWN 0x23 + +#define INBOUND_NOT_COMING_UP 0x31 +#define INBOUND_COMING_UP 0x32 + +/* + * Offsets for the mcpm_sync_struct members, for use in asm. + * We don't want to make them global to the kernel via asm-offsets.c. + */ +#define MCPM_SYNC_CLUSTER_CPUS 0 +#define MCPM_SYNC_CPU_SIZE __CACHE_WRITEBACK_GRANULE +#define MCPM_SYNC_CLUSTER_CLUSTER \ + (MCPM_SYNC_CLUSTER_CPUS + MCPM_SYNC_CPU_SIZE * MAX_CPUS_PER_CLUSTER) +#define MCPM_SYNC_CLUSTER_INBOUND \ + (MCPM_SYNC_CLUSTER_CLUSTER + __CACHE_WRITEBACK_GRANULE) +#define MCPM_SYNC_CLUSTER_SIZE \ + (MCPM_SYNC_CLUSTER_INBOUND + __CACHE_WRITEBACK_GRANULE) + #endif diff --git a/arch/arm/kernel/asm-offsets.c b/arch/arm/kernel/asm-offsets.c index 923eec7105c..1bed82a0a9e 100644 --- a/arch/arm/kernel/asm-offsets.c +++ b/arch/arm/kernel/asm-offsets.c @@ -149,6 +149,9 @@ int main(void) DEFINE(DMA_BIDIRECTIONAL, DMA_BIDIRECTIONAL); DEFINE(DMA_TO_DEVICE, DMA_TO_DEVICE); DEFINE(DMA_FROM_DEVICE, DMA_FROM_DEVICE); + BLANK(); + DEFINE(CACHE_WRITEBACK_GRANULE, __CACHE_WRITEBACK_GRANULE); + BLANK(); #ifdef CONFIG_KVM_ARM_HOST DEFINE(VCPU_KVM, offsetof(struct kvm_vcpu, kvm)); DEFINE(VCPU_MIDR, offsetof(struct kvm_vcpu, arch.midr)); |