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linux/arch/arm/include/asm/mcpm.h
Nicolas Pitre d0cdef6e87 ARM: 7842/1: MCPM: don't explode if invoked without being initialized first 
Currently mcpm_cpu_power_down() and mcpm_cpu_suspend() trigger BUG()
if mcpm_platform_register() is not called beforehand.  This may occur
for many reasons such as some incomplete device tree passed to the kernel
or the like.

Let's be nicer to users and avoid killing the kernel if that happens by
logging a warning and returning to the caller.  The mcpm_cpu_suspend()
user is already set to deal with this situation, and so is cpu_die()
invoking mcpm_cpu_die().

The problematic case would have been the B.L switcher's usage of
mcpm_cpu_power_down(), however it has to call mcpm_cpu_power_up() first
which is already set to catch an error resulting from a missing
mcpm_platform_register() call.

Signed-off-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
2013-10-03 10:36:37 +01:00

216 lines
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/*
* arch/arm/include/asm/mcpm.h
*
* Created by: Nicolas Pitre, April 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.
*/
#ifndef MCPM_H
#define MCPM_H
/*
* Maximum number of possible clusters / CPUs per cluster.
*
* This should be sufficient for quite a while, while keeping the
* (assembly) code simpler. When this starts to grow then we'll have
* to consider dynamic allocation.
*/
#define MAX_CPUS_PER_CLUSTER 4
#define MAX_NR_CLUSTERS 2
#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.
*/
extern void mcpm_entry_point(void);
/*
* This is used to indicate where the given CPU from given cluster should
* branch once it is ready to re-enter the kernel using ptr, or NULL if it
* should be gated. A gated CPU is held in a WFE loop until its vector
* becomes non NULL.
*/
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.
*
* On success this does not return. Re-entry in the kernel is expected
* via mcpm_entry_point.
*
* This will return if mcpm_platform_register() has not been called
* previously in which case the caller should take appropriate action.
*/
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.
*
* On success this does not return. Re-entry in the kernel is expected
* via mcpm_entry_point.
*
* This will return if mcpm_platform_register() has not been called
* previously in which case the caller should take appropriate action.
*/
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);
/* 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));
void __init mcpm_smp_set_ops(void);
#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
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