Commit 7c2b8605 authored by Nicolas Pitre's avatar Nicolas Pitre

ARM: mcpm: introduce the CPU/cluster power API

This is the basic API used to handle the powering up/down of individual
CPUs in a (multi-)cluster system.  The platform specific backend
implementation has the responsibility to also handle the cluster level
power as well when the first/last CPU in a cluster is brought up/down.
Signed-off-by: default avatarNicolas Pitre <nico@linaro.org>
Reviewed-by: default avatarSantosh Shilimkar <santosh.shilimkar@ti.com>
Reviewed-by: default avatarWill Deacon <will.deacon@arm.com>
parent e8db288e
......@@ -9,8 +9,13 @@
* published by the Free Software Foundation.
*/
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/irqflags.h>
#include <asm/mcpm.h>
#include <asm/cacheflush.h>
#include <asm/idmap.h>
extern unsigned long mcpm_entry_vectors[MAX_NR_CLUSTERS][MAX_CPUS_PER_CLUSTER];
......@@ -20,3 +25,89 @@ void mcpm_set_entry_vector(unsigned cpu, unsigned cluster, void *ptr)
mcpm_entry_vectors[cluster][cpu] = val;
sync_cache_w(&mcpm_entry_vectors[cluster][cpu]);
}
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;
}
int mcpm_cpu_power_up(unsigned int cpu, unsigned int cluster)
{
if (!platform_ops)
return -EUNATCH; /* try not to shadow power_up errors */
might_sleep();
return platform_ops->power_up(cpu, cluster);
}
typedef void (*phys_reset_t)(unsigned long);
void mcpm_cpu_power_down(void)
{
phys_reset_t phys_reset;
BUG_ON(!platform_ops);
BUG_ON(!irqs_disabled());
/*
* Do this before calling into the power_down method,
* as it might not always be safe to do afterwards.
*/
setup_mm_for_reboot();
platform_ops->power_down();
/*
* It is possible for a power_up request to happen concurrently
* with a power_down request for the same CPU. In this case the
* power_down method might not be able to actually enter a
* powered down state with the WFI instruction if the power_up
* method has removed the required reset condition. The
* power_down method is then allowed to return. We must perform
* a re-entry in the kernel as if the power_up method just had
* deasserted reset on the CPU.
*
* To simplify race issues, the platform specific implementation
* must accommodate for the possibility of unordered calls to
* power_down and power_up with a usage count. Therefore, if a
* call to power_up is issued for a CPU that is not down, then
* the next call to power_down must not attempt a full shutdown
* but only do the minimum (normally disabling L1 cache and CPU
* coherency) and return just as if a concurrent power_up request
* had happened as described above.
*/
phys_reset = (phys_reset_t)(unsigned long)virt_to_phys(cpu_reset);
phys_reset(virt_to_phys(mcpm_entry_point));
/* should never get here */
BUG();
}
void mcpm_cpu_suspend(u64 expected_residency)
{
phys_reset_t phys_reset;
BUG_ON(!platform_ops);
BUG_ON(!irqs_disabled());
/* Very similar to mcpm_cpu_power_down() */
setup_mm_for_reboot();
platform_ops->suspend(expected_residency);
phys_reset = (phys_reset_t)(unsigned long)virt_to_phys(cpu_reset);
phys_reset(virt_to_phys(mcpm_entry_point));
BUG();
}
int mcpm_cpu_powered_up(void)
{
if (!platform_ops)
return -EUNATCH;
if (platform_ops->powered_up)
platform_ops->powered_up();
return 0;
}
......@@ -38,5 +38,97 @@ extern void mcpm_entry_point(void);
*/
void mcpm_set_entry_vector(unsigned cpu, unsigned cluster, void *ptr);
/*
* CPU/cluster power operations API for higher subsystems to use.
*/
/**
* mcpm_cpu_power_up - make given CPU in given cluster runable
*
* @cpu: CPU number within given cluster
* @cluster: cluster number for the CPU
*
* The identified CPU is brought out of reset. If the cluster was powered
* down then it is brought up as well, taking care not to let the other CPUs
* in the cluster run, and ensuring appropriate cluster setup.
*
* Caller must ensure the appropriate entry vector is initialized with
* mcpm_set_entry_vector() prior to calling this.
*
* This must be called in a sleepable context. However, the implementation
* is strongly encouraged to return early and let the operation happen
* asynchronously, especially when significant delays are expected.
*
* If the operation cannot be performed then an error code is returned.
*/
int mcpm_cpu_power_up(unsigned int cpu, unsigned int cluster);
/**
* mcpm_cpu_power_down - power the calling CPU down
*
* The calling CPU is powered down.
*
* If this CPU is found to be the "last man standing" in the cluster
* then the cluster is prepared for power-down too.
*
* This must be called with interrupts disabled.
*
* This does not return. Re-entry in the kernel is expected via
* mcpm_entry_point.
*/
void mcpm_cpu_power_down(void);
/**
* mcpm_cpu_suspend - bring the calling CPU in a suspended state
*
* @expected_residency: duration in microseconds the CPU is expected
* to remain suspended, or 0 if unknown/infinity.
*
* The calling CPU is suspended. The expected residency argument is used
* as a hint by the platform specific backend to implement the appropriate
* sleep state level according to the knowledge it has on wake-up latency
* for the given hardware.
*
* If this CPU is found to be the "last man standing" in the cluster
* then the cluster may be prepared for power-down too, if the expected
* residency makes it worthwhile.
*
* This must be called with interrupts disabled.
*
* This does not return. Re-entry in the kernel is expected via
* mcpm_entry_point.
*/
void mcpm_cpu_suspend(u64 expected_residency);
/**
* mcpm_cpu_powered_up - housekeeping workafter a CPU has been powered up
*
* This lets the platform specific backend code perform needed housekeeping
* work. This must be called by the newly activated CPU as soon as it is
* fully operational in kernel space, before it enables interrupts.
*
* If the operation cannot be performed then an error code is returned.
*/
int mcpm_cpu_powered_up(void);
/*
* Platform specific methods used in the implementation of the above API.
*/
struct mcpm_platform_ops {
int (*power_up)(unsigned int cpu, unsigned int cluster);
void (*power_down)(void);
void (*suspend)(u64);
void (*powered_up)(void);
};
/**
* mcpm_platform_register - register platform specific power methods
*
* @ops: mcpm_platform_ops structure to register
*
* An error is returned if the registration has been done previously.
*/
int __init mcpm_platform_register(const struct mcpm_platform_ops *ops);
#endif /* ! __ASSEMBLY__ */
#endif
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment