The only requirement the scheduler has on cluster IDs is that they must
be unique. When enumerating the topology based on MPIDR information the
kernel currently generates cluster IDs by using the first level of
affinity above the core ID (either level one or two depending on if the
core has multiple threads) however the ARMv8 architecture allows for up
to three levels of affinity. This means that an ARMv8 system may
contain cores which have MPIDRs identical other than affinity level
three which with current code will cause us to report multiple cores
with the same identification to the scheduler in violation of its
uniqueness requirement.
Ensure that we do not violate the scheduler requirements on systems that
uses all the affinity levels by incorporating both affinity levels two
and three into the cluser ID when the cores are not threaded.
While no currently known hardware uses multi-level clusters it is better
to program defensively, this will help ease bringup of systems that have
them and will ensure that things like distribution install media do not
need to be respun to replace kernels in order to deploy such systems.
In the worst case the system will work but perform suboptimally until a
kernel modified to handle the new topology better is installed, in the
best case this will be an adequate description of such topologies for
the scheduler to perform well.
Signed-off-by: Mark Brown <broonie@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Create cpu topology based on MPIDR. When hardware sets MPIDR to sane
values, this method will always work. Therefore it should also work well
as the fallback method. [1]
When we have multiple processing elements in the system, we create
the cpu topology by mapping each affinity level (from lowest to highest)
to threads (if they exist), cores, and clusters.
[1] http://www.spinics.net/lists/arm-kernel/msg317445.html
Acked-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Zi Shen Lim <zlim@broadcom.com>
Signed-off-by: Mark Brown <broonie@linaro.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Add support for parsing the explicit topology bindings to discover the
topology of the system.
Since it is not currently clear how to map multi-level clusters for the
scheduler all leaf clusters are presented to the scheduler at the same
level. This should be enough to provide good support for current systems.
Signed-off-by: Mark Brown <broonie@linaro.org>
Reviewed-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
As a legacy of the way 32 bit ARM did things the topology code uses a null
topology map by default and then overwrites it by mapping cores with no
information to a cluster by themselves later. In order to make it simpler
to reset things as part of recovering from parse failures in firmware
information directly set this configuration on init. A core will always be
its own sibling so there should be no risk of confusion with firmware
provided information.
Signed-off-by: Mark Brown <broonie@linaro.org>
Reviewed-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Add basic CPU topology support to arm64, based on the existing pre-v8
code and some work done by Mark Hambleton. This patch does not
implement any topology discovery support since that should be based on
information from firmware, it merely implements the scaffolding for
integration of topology support in the architecture.
No locking of the topology data is done since it is only modified during
CPU bringup with external serialisation from the SMP code.
The goal is to separate the architecture hookup for providing topology
information from the DT parsing in order to ease review and avoid
blocking the architecture code (which will be built on by other work)
with the DT code review by providing something simple and basic.
Following patches will implement support for interpreting topology
information from MPIDR and for parsing the DT topology bindings for ARM,
similar patches will be needed for ACPI.
Signed-off-by: Mark Brown <broonie@linaro.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
[catalin.marinas@arm.com: removed CONFIG_CPU_TOPOLOGY, always on if SMP]
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
