ARM64_CPU_SUSPEND config option was introduced to make code providing
context save/restore selectable only on platforms requiring power
management capabilities.
Currently ARM64_CPU_SUSPEND depends on the PM_SLEEP config option which
in turn is set by the SUSPEND config option.
The introduction of CPU_IDLE for arm64 requires that code configured
by ARM64_CPU_SUSPEND (context save/restore) should be compiled in
in order to enable the CPU idle driver to rely on CPU operations
carrying out context save/restore.
The ARM64_CPUIDLE config option (ARM64 generic idle driver) is therefore
forced to select ARM64_CPU_SUSPEND, even if there may be (ie PM_SLEEP)
failed dependencies, which is not a clean way of handling the kernel
configuration option.
For these reasons, this patch removes the ARM64_CPU_SUSPEND config option
and makes the context save/restore dependent on CPU_PM, which is selected
whenever either SUSPEND or CPU_IDLE are configured, cleaning up dependencies
in the process.
This way, code previously configured through ARM64_CPU_SUSPEND is
compiled in whenever a power management subsystem requires it to be
present in the kernel (SUSPEND || CPU_IDLE), which is the behaviour
expected on ARM64 kernels.
The cpu_suspend and cpu_init_idle CPU operations are added only if
CPU_IDLE is selected, since they are CPU_IDLE specific methods and
should be grouped and defined accordingly.
PSCI CPU operations are updated to reflect the introduced changes.
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Function prototypes are never definitions, so remove any 'extern' keyword
from the funcion prototypes in cpu_ops.h. Fixes warnings emited by
checkpatch.
Signed-off-by: Geoff Levand <geoff@infradead.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
The CPUidle subsystem on ARM64 machines requires the idle states
implementation back-end to initialize idle states parameter upon
boot. This patch adds a hook in the CPU operations structure that
should be initialized by the CPU operations back-end in order to
provide a function that initializes cpu idle states.
This patch also adds the infrastructure to arm64 kernel required
to export the CPU operations based initialization interface, so
that drivers (ie CPUidle) can use it when they are initialized
at probe time.
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
PSCIv0.2 adds a new function called AFFINITY_INFO, which
can be used to query if a specified CPU has actually gone
offline. Calling this function via cpu_kill ensures that
a CPU has quiesced after a call to cpu_die. This helps
prevent the CPU from doing arbitrary bad things when data
or instructions are clobbered (as happens with kexec)
in the window between a CPU announcing that it is dead
and said CPU leaving the kernel.
Signed-off-by: Ashwin Chaugule <ashwin.chaugule@linaro.org>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Kernel subsystems like CPU idle and suspend to RAM require a generic
mechanism to suspend a processor, save its context and put it into
a quiescent state. The cpu_{suspend}/{resume} implementation provides
such a framework through a kernel interface allowing to save/restore
registers, flush the context to DRAM and suspend/resume to/from
low-power states where processor context may be lost.
The CPU suspend implementation relies on the suspend protocol registered
in CPU operations to carry out a suspend request after context is
saved and flushed to DRAM. The cpu_suspend interface:
int cpu_suspend(unsigned long arg);
allows to pass an opaque parameter that is handed over to the suspend CPU
operations back-end so that it can take action according to the
semantics attached to it. The arg parameter allows suspend to RAM and CPU
idle drivers to communicate to suspend protocol back-ends; it requires
standardization so that the interface can be reused seamlessly across
systems, paving the way for generic drivers.
Context memory is allocated on the stack, whose address is stashed in a
per-cpu variable to keep track of it and passed to core functions that
save/restore the registers required by the architecture.
Even though, upon successful execution, the cpu_suspend function shuts
down the suspending processor, the warm boot resume mechanism, based
on the cpu_resume function, makes the resume path operate as a
cpu_suspend function return, so that cpu_suspend can be treated as a C
function by the caller, which simplifies coding the PM drivers that rely
on the cpu_suspend API.
Upon context save, the minimal amount of memory is flushed to DRAM so
that it can be retrieved when the MMU is off and caches are not searched.
The suspend CPU operation, depending on the required operations (eg CPU vs
Cluster shutdown) is in charge of flushing the cache hierarchy either
implicitly (by calling firmware implementations like PSCI) or explicitly
by executing the required cache maintainance functions.
Debug exceptions are disabled during cpu_{suspend}/{resume} operations
so that debug registers can be saved and restored properly preventing
preemption from debug agents enabled in the kernel.
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
This patch adds the basic infrastructure necessary to support
CPU_HOTPLUG on arm64, based on the arm implementation. Actual hotplug
support will depend on an implementation's cpu_operations (e.g. PSCI).
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
With the advent of CPU_HOTPLUG, the enable-method property for CPU0 may
tells us something useful (i.e. how to hotplug it back on), so we must
read it along with all the enable-method for all the other CPUs. Even
on UP the enable-method may tell us useful information (e.g. if a core
has some mechanism that might be usable for cpuidle), so we should
always read it.
This patch factors out the reading of the enable method, and ensures
that CPU0's enable method is read regardless of whether the kernel is
built with SMP support.
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
The arm64 kernel has an internal holding pen, which is necessary for
some systems where we can't bring CPUs online individually and must hold
multiple CPUs in a safe area until the kernel is able to handle them.
The current SMP infrastructure for arm64 is closely coupled to this
holding pen, and alternative boot methods must launch CPUs into the pen,
where they sit before they are launched into the kernel proper.
With PSCI (and possibly other future boot methods), we can bring CPUs
online individually, and need not perform the secondary_holding_pen
dance. Instead, this patch factors the holding pen management code out
to the spin-table boot method code, as it is the only boot method
requiring the pen.
A new entry point for secondaries, secondary_entry is added for other
boot methods to use, which bypasses the holding pen and its associated
overhead when bringing CPUs online. The smp.pen.text section is also
removed, as the pen can live in head.text without problem.
The cpu_operations structure is extended with two new functions,
cpu_boot and cpu_postboot, for bringing a cpu into the kernel and
performing any post-boot cleanup required by a bootmethod (e.g.
resetting the secondary_holding_pen_release to INVALID_HWID).
Documentation is added for cpu_operations.
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
For hotplug support, we're going to want a place to store operations
that do more than bring CPUs online, and it makes sense to group these
with our current smp_enable_ops. For cpuidle support, we'll want to
group additional functions, and we may want them even for UP kernels.
This patch renames smp_enable_ops to the more general cpu_operations,
and pulls the definitions out of smp code such that they can be used in
UP kernels. While we're at it, fix up instances of the cpu parameter to
be an unsigned int, drop the init markings and rename the *_cpu
functions to cpu_* to reduce future churn when cpu_operations is
extended.
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Lorenzo Pieralisi
Geoff Levand
Ashwin Chaugule
Mark Rutland