diff options
| author | Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> | 2023-01-25 12:34:18 +0100 |
|---|---|---|
| committer | Rafael J. Wysocki <rafael.j.wysocki@intel.com> | 2023-02-13 17:15:42 +0100 |
| commit | f9901f64536c39f699e6ed228c5e64e7e7ce8708 (patch) | |
| tree | 9235f2f0f8b6d839cffc3250ab44ea5a26e0770a /drivers/cpuidle/Kconfig.arm | |
| parent | 41204a607679ccca7eabff9f2871b969d6ef2ce3 (diff) | |
| download | lwn-f9901f64536c39f699e6ed228c5e64e7e7ce8708.tar.gz lwn-f9901f64536c39f699e6ed228c5e64e7e7ce8708.zip | |
cpuidle: psci: Do not suspend topology CPUs on PREEMPT_RT
The runtime Power Management of CPU topology is not compatible with
PREEMPT_RT:
1. Core cpuidle path disables IRQs.
2. Core cpuidle calls cpuidle-psci.
3. cpuidle-psci in __psci_enter_domain_idle_state() calls
pm_runtime_put_sync_suspend() and pm_runtime_get_sync() which use
spinlocks (which are sleeping on PREEMPT_RT).
Deep sleep modes are not a priority of Realtime kernels because the
latencies might become unpredictable. On the other hand the PSCI CPU
idle power domain is a parent of other devices and power domain
controllers, thus it cannot be simply skipped (e.g. on Qualcomm SM8250).
Disable the idle callbacks in cpuidle-psci and mark the domain as
always on. This is a trade-off between making PREEMPT_RT working and
still having a proper power domain hierarchy in the system.
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
Tested-by: Adrien Thierry <athierry@redhat.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'drivers/cpuidle/Kconfig.arm')
| -rw-r--r-- | drivers/cpuidle/Kconfig.arm | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/drivers/cpuidle/Kconfig.arm b/drivers/cpuidle/Kconfig.arm index f0714a32921e..a1ee475d180d 100644 --- a/drivers/cpuidle/Kconfig.arm +++ b/drivers/cpuidle/Kconfig.arm @@ -24,6 +24,14 @@ config ARM_PSCI_CPUIDLE It provides an idle driver that is capable of detecting and managing idle states through the PSCI firmware interface. + The driver has limitations when used with PREEMPT_RT: + - If the idle states are described with the non-hierarchical layout, + all idle states are still available. + + - If the idle states are described with the hierarchical layout, + only the idle states defined per CPU are available, but not the ones + being shared among a group of CPUs (aka cluster idle states). + config ARM_PSCI_CPUIDLE_DOMAIN bool "PSCI CPU idle Domain" depends on ARM_PSCI_CPUIDLE |