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authorNicolas Pitre <nicolas.pitre@linaro.org>2012-09-20 16:05:37 -0400
committerNicolas Pitre <nicolas.pitre@linaro.org>2013-04-24 10:36:59 -0400
commit7c2b860534d02d11923dd0504b961f21508173f1 (patch)
tree643030cebe48d267e67eb9b533284db881ef99a5 /arch/arm
parente8db288e05e588ad3f416b3a24354d60d02f35f2 (diff)
downloadvexpress-lsk-7c2b860534d02d11923dd0504b961f21508173f1.tar.gz
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: Nicolas Pitre <nico@linaro.org> Reviewed-by: Santosh Shilimkar <santosh.shilimkar@ti.com> Reviewed-by: Will Deacon <will.deacon@arm.com>
Diffstat (limited to 'arch/arm')
-rw-r--r--arch/arm/common/mcpm_entry.c91
-rw-r--r--arch/arm/include/asm/mcpm.h92
2 files changed, 183 insertions, 0 deletions
diff --git a/arch/arm/common/mcpm_entry.c b/arch/arm/common/mcpm_entry.c
index 7cbf70051ea..5d72889a58a 100644
--- a/arch/arm/common/mcpm_entry.c
+++ b/arch/arm/common/mcpm_entry.c
@@ -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;
+}
diff --git a/arch/arm/include/asm/mcpm.h b/arch/arm/include/asm/mcpm.h
index 470a417d135..627761fce78 100644
--- a/arch/arm/include/asm/mcpm.h
+++ b/arch/arm/include/asm/mcpm.h
@@ -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