linux/arch/arm/common/mcpm_entry.c

457 lines
13 KiB
C
Raw Normal View History

// SPDX-License-Identifier: GPL-2.0-only
/*
* arch/arm/common/mcpm_entry.c -- entry point for multi-cluster PM
*
* Created by: Nicolas Pitre, March 2012
* Copyright: (C) 2012-2013 Linaro Limited
*/
#include <linux/export.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/irqflags.h>
#include <linux/cpu_pm.h>
#include <asm/mcpm.h>
#include <asm/cacheflush.h>
#include <asm/idmap.h>
ARM: mcpm: introduce helpers for platform coherency exit/setup This provides helper methods to coordinate between CPUs coming down and CPUs going up, as well as documentation on the used algorithms, so that cluster teardown and setup operations are not done for a cluster simultaneously. For use in the power_down() implementation: * __mcpm_cpu_going_down(unsigned int cluster, unsigned int cpu) * __mcpm_outbound_enter_critical(unsigned int cluster) * __mcpm_outbound_leave_critical(unsigned int cluster) * __mcpm_cpu_down(unsigned int cluster, unsigned int cpu) The power_up_setup() helper should do platform-specific setup in preparation for turning the CPU on, such as invalidating local caches or entering coherency. It must be assembler for now, since it must run before the MMU can be switched on. It is passed the affinity level for which initialization should be performed. Because the mcpm_sync_struct content is looked-up and modified with the cache enabled or disabled depending on the code path, it is crucial to always ensure proper cache maintenance to update main memory right away. The sync_cache_*() helpers are used to that end. Also, in order to prevent a cached writer from interfering with an adjacent non-cached writer, we ensure each state variable is located to a separate cache line. Thanks to Nicolas Pitre and Achin Gupta for the help with this patch. Signed-off-by: Dave Martin <dave.martin@linaro.org> Signed-off-by: Nicolas Pitre <nico@linaro.org> Reviewed-by: Will Deacon <will.deacon@arm.com>
2012-07-17 15:25:42 +02:00
#include <asm/cputype.h>
#include <asm/suspend.h>
/*
* The public API for this code is documented in arch/arm/include/asm/mcpm.h.
* For a comprehensive description of the main algorithm used here, please
* see Documentation/arm/cluster-pm-race-avoidance.rst.
*/
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.
*/
static 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.
*/
static 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);
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).
*/
static 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);
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.
*/
static 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;
}
static 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_entry_vectors[MAX_NR_CLUSTERS][MAX_CPUS_PER_CLUSTER];
void mcpm_set_entry_vector(unsigned cpu, unsigned cluster, void *ptr)
{
unsigned long val = ptr ? __pa_symbol(ptr) : 0;
mcpm_entry_vectors[cluster][cpu] = val;
sync_cache_w(&mcpm_entry_vectors[cluster][cpu]);
}
extern unsigned long mcpm_entry_early_pokes[MAX_NR_CLUSTERS][MAX_CPUS_PER_CLUSTER][2];
void mcpm_set_early_poke(unsigned cpu, unsigned cluster,
unsigned long poke_phys_addr, unsigned long poke_val)
{
unsigned long *poke = &mcpm_entry_early_pokes[cluster][cpu][0];
poke[0] = poke_phys_addr;
poke[1] = poke_val;
__sync_cache_range_w(poke, 2 * sizeof(*poke));
}
static const struct mcpm_platform_ops *platform_ops;
int __init mcpm_platform_register(const struct mcpm_platform_ops *ops)
{
if (platform_ops)
return -EBUSY;
platform_ops = ops;
return 0;
}
bool mcpm_is_available(void)
{
return (platform_ops) ? true : false;
}
EXPORT_SYMBOL_GPL(mcpm_is_available);
/*
* We can't use regular spinlocks. In the switcher case, it is possible
* for an outbound CPU to call power_down() after its inbound counterpart
* is already live using the same logical CPU number which trips lockdep
* debugging.
*/
static arch_spinlock_t mcpm_lock = __ARCH_SPIN_LOCK_UNLOCKED;
static int mcpm_cpu_use_count[MAX_NR_CLUSTERS][MAX_CPUS_PER_CLUSTER];
static inline bool mcpm_cluster_unused(unsigned int cluster)
{
int i, cnt;
for (i = 0, cnt = 0; i < MAX_CPUS_PER_CLUSTER; i++)
cnt |= mcpm_cpu_use_count[cluster][i];
return !cnt;
}
int mcpm_cpu_power_up(unsigned int cpu, unsigned int cluster)
{
bool cpu_is_down, cluster_is_down;
int ret = 0;
pr_debug("%s: cpu %u cluster %u\n", __func__, cpu, cluster);
if (!platform_ops)
return -EUNATCH; /* try not to shadow power_up errors */
might_sleep();
/*
* Since this is called with IRQs enabled, and no arch_spin_lock_irq
* variant exists, we need to disable IRQs manually here.
*/
local_irq_disable();
arch_spin_lock(&mcpm_lock);
cpu_is_down = !mcpm_cpu_use_count[cluster][cpu];
cluster_is_down = mcpm_cluster_unused(cluster);
mcpm_cpu_use_count[cluster][cpu]++;
/*
* The only possible values are:
* 0 = CPU down
* 1 = CPU (still) up
* 2 = CPU requested to be up before it had a chance
* to actually make itself down.
* Any other value is a bug.
*/
BUG_ON(mcpm_cpu_use_count[cluster][cpu] != 1 &&
mcpm_cpu_use_count[cluster][cpu] != 2);
if (cluster_is_down)
ret = platform_ops->cluster_powerup(cluster);
if (cpu_is_down && !ret)
ret = platform_ops->cpu_powerup(cpu, cluster);
arch_spin_unlock(&mcpm_lock);
local_irq_enable();
return ret;
}
typedef typeof(cpu_reset) phys_reset_t;
void mcpm_cpu_power_down(void)
{
unsigned int mpidr, cpu, cluster;
bool cpu_going_down, last_man;
phys_reset_t phys_reset;
mpidr = read_cpuid_mpidr();
cpu = MPIDR_AFFINITY_LEVEL(mpidr, 0);
cluster = MPIDR_AFFINITY_LEVEL(mpidr, 1);
pr_debug("%s: cpu %u cluster %u\n", __func__, cpu, cluster);
if (WARN_ON_ONCE(!platform_ops))
return;
BUG_ON(!irqs_disabled());
setup_mm_for_reboot();
__mcpm_cpu_going_down(cpu, cluster);
arch_spin_lock(&mcpm_lock);
BUG_ON(__mcpm_cluster_state(cluster) != CLUSTER_UP);
mcpm_cpu_use_count[cluster][cpu]--;
BUG_ON(mcpm_cpu_use_count[cluster][cpu] != 0 &&
mcpm_cpu_use_count[cluster][cpu] != 1);
cpu_going_down = !mcpm_cpu_use_count[cluster][cpu];
last_man = mcpm_cluster_unused(cluster);
if (last_man && __mcpm_outbound_enter_critical(cpu, cluster)) {
platform_ops->cpu_powerdown_prepare(cpu, cluster);
platform_ops->cluster_powerdown_prepare(cluster);
arch_spin_unlock(&mcpm_lock);
platform_ops->cluster_cache_disable();
__mcpm_outbound_leave_critical(cluster, CLUSTER_DOWN);
} else {
if (cpu_going_down)
platform_ops->cpu_powerdown_prepare(cpu, cluster);
arch_spin_unlock(&mcpm_lock);
/*
* If cpu_going_down is false here, that means a power_up
* request raced ahead of us. Even if we do not want to
* shut this CPU down, the caller still expects execution
* to return through the system resume entry path, like
* when the WFI is aborted due to a new IRQ or the like..
* So let's continue with cache cleaning in all cases.
*/
platform_ops->cpu_cache_disable();
}
__mcpm_cpu_down(cpu, cluster);
/* Now we are prepared for power-down, do it: */
if (cpu_going_down)
wfi();
/*
* It is possible for a power_up request to happen concurrently
* with a power_down request for the same CPU. In this case the
* CPU might not be able to actually enter a powered down state
* with the WFI instruction if the power_up request has removed
* the required reset condition. We must perform a re-entry in
* the kernel as if the power_up method just had deasserted reset
* on the CPU.
*/
phys_reset = (phys_reset_t)(unsigned long)__pa_symbol(cpu_reset);
phys_reset(__pa_symbol(mcpm_entry_point), false);
/* should never get here */
BUG();
}
int mcpm_wait_for_cpu_powerdown(unsigned int cpu, unsigned int cluster)
{
int ret;
if (WARN_ON_ONCE(!platform_ops || !platform_ops->wait_for_powerdown))
return -EUNATCH;
ret = platform_ops->wait_for_powerdown(cpu, cluster);
if (ret)
pr_warn("%s: cpu %u, cluster %u failed to power down (%d)\n",
__func__, cpu, cluster, ret);
return ret;
}
void mcpm_cpu_suspend(void)
{
if (WARN_ON_ONCE(!platform_ops))
return;
/* Some platforms might have to enable special resume modes, etc. */
if (platform_ops->cpu_suspend_prepare) {
unsigned int mpidr = read_cpuid_mpidr();
unsigned int cpu = MPIDR_AFFINITY_LEVEL(mpidr, 0);
unsigned int cluster = MPIDR_AFFINITY_LEVEL(mpidr, 1);
arch_spin_lock(&mcpm_lock);
platform_ops->cpu_suspend_prepare(cpu, cluster);
arch_spin_unlock(&mcpm_lock);
}
mcpm_cpu_power_down();
}
int mcpm_cpu_powered_up(void)
{
unsigned int mpidr, cpu, cluster;
bool cpu_was_down, first_man;
unsigned long flags;
if (!platform_ops)
return -EUNATCH;
mpidr = read_cpuid_mpidr();
cpu = MPIDR_AFFINITY_LEVEL(mpidr, 0);
cluster = MPIDR_AFFINITY_LEVEL(mpidr, 1);
local_irq_save(flags);
arch_spin_lock(&mcpm_lock);
cpu_was_down = !mcpm_cpu_use_count[cluster][cpu];
first_man = mcpm_cluster_unused(cluster);
if (first_man && platform_ops->cluster_is_up)
platform_ops->cluster_is_up(cluster);
if (cpu_was_down)
mcpm_cpu_use_count[cluster][cpu] = 1;
if (platform_ops->cpu_is_up)
platform_ops->cpu_is_up(cpu, cluster);
arch_spin_unlock(&mcpm_lock);
local_irq_restore(flags);
return 0;
}
ARM: mcpm: introduce helpers for platform coherency exit/setup This provides helper methods to coordinate between CPUs coming down and CPUs going up, as well as documentation on the used algorithms, so that cluster teardown and setup operations are not done for a cluster simultaneously. For use in the power_down() implementation: * __mcpm_cpu_going_down(unsigned int cluster, unsigned int cpu) * __mcpm_outbound_enter_critical(unsigned int cluster) * __mcpm_outbound_leave_critical(unsigned int cluster) * __mcpm_cpu_down(unsigned int cluster, unsigned int cpu) The power_up_setup() helper should do platform-specific setup in preparation for turning the CPU on, such as invalidating local caches or entering coherency. It must be assembler for now, since it must run before the MMU can be switched on. It is passed the affinity level for which initialization should be performed. Because the mcpm_sync_struct content is looked-up and modified with the cache enabled or disabled depending on the code path, it is crucial to always ensure proper cache maintenance to update main memory right away. The sync_cache_*() helpers are used to that end. Also, in order to prevent a cached writer from interfering with an adjacent non-cached writer, we ensure each state variable is located to a separate cache line. Thanks to Nicolas Pitre and Achin Gupta for the help with this patch. Signed-off-by: Dave Martin <dave.martin@linaro.org> Signed-off-by: Nicolas Pitre <nico@linaro.org> Reviewed-by: Will Deacon <will.deacon@arm.com>
2012-07-17 15:25:42 +02:00
#ifdef CONFIG_ARM_CPU_SUSPEND
static int __init nocache_trampoline(unsigned long _arg)
{
void (*cache_disable)(void) = (void *)_arg;
unsigned int mpidr = read_cpuid_mpidr();
unsigned int cpu = MPIDR_AFFINITY_LEVEL(mpidr, 0);
unsigned int cluster = MPIDR_AFFINITY_LEVEL(mpidr, 1);
phys_reset_t phys_reset;
mcpm_set_entry_vector(cpu, cluster, cpu_resume_no_hyp);
setup_mm_for_reboot();
__mcpm_cpu_going_down(cpu, cluster);
BUG_ON(!__mcpm_outbound_enter_critical(cpu, cluster));
cache_disable();
__mcpm_outbound_leave_critical(cluster, CLUSTER_DOWN);
__mcpm_cpu_down(cpu, cluster);
phys_reset = (phys_reset_t)(unsigned long)__pa_symbol(cpu_reset);
phys_reset(__pa_symbol(mcpm_entry_point), false);
BUG();
}
int __init mcpm_loopback(void (*cache_disable)(void))
{
int ret;
/*
* We're going to soft-restart the current CPU through the
* low-level MCPM code by leveraging the suspend/resume
* infrastructure. Let's play it safe by using cpu_pm_enter()
* in case the CPU init code path resets the VFP or similar.
*/
local_irq_disable();
local_fiq_disable();
ret = cpu_pm_enter();
if (!ret) {
ret = cpu_suspend((unsigned long)cache_disable, nocache_trampoline);
cpu_pm_exit();
}
local_fiq_enable();
local_irq_enable();
if (ret)
pr_err("%s returned %d\n", __func__, ret);
return ret;
}
#endif
ARM: mcpm: introduce helpers for platform coherency exit/setup This provides helper methods to coordinate between CPUs coming down and CPUs going up, as well as documentation on the used algorithms, so that cluster teardown and setup operations are not done for a cluster simultaneously. For use in the power_down() implementation: * __mcpm_cpu_going_down(unsigned int cluster, unsigned int cpu) * __mcpm_outbound_enter_critical(unsigned int cluster) * __mcpm_outbound_leave_critical(unsigned int cluster) * __mcpm_cpu_down(unsigned int cluster, unsigned int cpu) The power_up_setup() helper should do platform-specific setup in preparation for turning the CPU on, such as invalidating local caches or entering coherency. It must be assembler for now, since it must run before the MMU can be switched on. It is passed the affinity level for which initialization should be performed. Because the mcpm_sync_struct content is looked-up and modified with the cache enabled or disabled depending on the code path, it is crucial to always ensure proper cache maintenance to update main memory right away. The sync_cache_*() helpers are used to that end. Also, in order to prevent a cached writer from interfering with an adjacent non-cached writer, we ensure each state variable is located to a separate cache line. Thanks to Nicolas Pitre and Achin Gupta for the help with this patch. Signed-off-by: Dave Martin <dave.martin@linaro.org> Signed-off-by: Nicolas Pitre <nico@linaro.org> Reviewed-by: Will Deacon <will.deacon@arm.com>
2012-07-17 15:25:42 +02:00
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_cpu_use_count[this_cluster][i] = 1;
ARM: mcpm: introduce helpers for platform coherency exit/setup This provides helper methods to coordinate between CPUs coming down and CPUs going up, as well as documentation on the used algorithms, so that cluster teardown and setup operations are not done for a cluster simultaneously. For use in the power_down() implementation: * __mcpm_cpu_going_down(unsigned int cluster, unsigned int cpu) * __mcpm_outbound_enter_critical(unsigned int cluster) * __mcpm_outbound_leave_critical(unsigned int cluster) * __mcpm_cpu_down(unsigned int cluster, unsigned int cpu) The power_up_setup() helper should do platform-specific setup in preparation for turning the CPU on, such as invalidating local caches or entering coherency. It must be assembler for now, since it must run before the MMU can be switched on. It is passed the affinity level for which initialization should be performed. Because the mcpm_sync_struct content is looked-up and modified with the cache enabled or disabled depending on the code path, it is crucial to always ensure proper cache maintenance to update main memory right away. The sync_cache_*() helpers are used to that end. Also, in order to prevent a cached writer from interfering with an adjacent non-cached writer, we ensure each state variable is located to a separate cache line. Thanks to Nicolas Pitre and Achin Gupta for the help with this patch. Signed-off-by: Dave Martin <dave.martin@linaro.org> Signed-off-by: Nicolas Pitre <nico@linaro.org> Reviewed-by: Will Deacon <will.deacon@arm.com>
2012-07-17 15:25:42 +02:00
mcpm_sync.clusters[this_cluster].cpus[i].cpu = CPU_UP;
}
ARM: mcpm: introduce helpers for platform coherency exit/setup This provides helper methods to coordinate between CPUs coming down and CPUs going up, as well as documentation on the used algorithms, so that cluster teardown and setup operations are not done for a cluster simultaneously. For use in the power_down() implementation: * __mcpm_cpu_going_down(unsigned int cluster, unsigned int cpu) * __mcpm_outbound_enter_critical(unsigned int cluster) * __mcpm_outbound_leave_critical(unsigned int cluster) * __mcpm_cpu_down(unsigned int cluster, unsigned int cpu) The power_up_setup() helper should do platform-specific setup in preparation for turning the CPU on, such as invalidating local caches or entering coherency. It must be assembler for now, since it must run before the MMU can be switched on. It is passed the affinity level for which initialization should be performed. Because the mcpm_sync_struct content is looked-up and modified with the cache enabled or disabled depending on the code path, it is crucial to always ensure proper cache maintenance to update main memory right away. The sync_cache_*() helpers are used to that end. Also, in order to prevent a cached writer from interfering with an adjacent non-cached writer, we ensure each state variable is located to a separate cache line. Thanks to Nicolas Pitre and Achin Gupta for the help with this patch. Signed-off-by: Dave Martin <dave.martin@linaro.org> Signed-off-by: Nicolas Pitre <nico@linaro.org> Reviewed-by: Will Deacon <will.deacon@arm.com>
2012-07-17 15:25:42 +02:00
mcpm_sync.clusters[this_cluster].cluster = CLUSTER_UP;
sync_cache_w(&mcpm_sync);
if (power_up_setup) {
mcpm_power_up_setup_phys = __pa_symbol(power_up_setup);
ARM: mcpm: introduce helpers for platform coherency exit/setup This provides helper methods to coordinate between CPUs coming down and CPUs going up, as well as documentation on the used algorithms, so that cluster teardown and setup operations are not done for a cluster simultaneously. For use in the power_down() implementation: * __mcpm_cpu_going_down(unsigned int cluster, unsigned int cpu) * __mcpm_outbound_enter_critical(unsigned int cluster) * __mcpm_outbound_leave_critical(unsigned int cluster) * __mcpm_cpu_down(unsigned int cluster, unsigned int cpu) The power_up_setup() helper should do platform-specific setup in preparation for turning the CPU on, such as invalidating local caches or entering coherency. It must be assembler for now, since it must run before the MMU can be switched on. It is passed the affinity level for which initialization should be performed. Because the mcpm_sync_struct content is looked-up and modified with the cache enabled or disabled depending on the code path, it is crucial to always ensure proper cache maintenance to update main memory right away. The sync_cache_*() helpers are used to that end. Also, in order to prevent a cached writer from interfering with an adjacent non-cached writer, we ensure each state variable is located to a separate cache line. Thanks to Nicolas Pitre and Achin Gupta for the help with this patch. Signed-off-by: Dave Martin <dave.martin@linaro.org> Signed-off-by: Nicolas Pitre <nico@linaro.org> Reviewed-by: Will Deacon <will.deacon@arm.com>
2012-07-17 15:25:42 +02:00
sync_cache_w(&mcpm_power_up_setup_phys);
}
return 0;
}