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authorKrzysztof Kozlowski <krzysztof.kozlowski@linaro.org>2023-01-25 14:34:18 +0300
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2023-02-13 19:15:42 +0300
commitf9901f64536c39f699e6ed228c5e64e7e7ce8708 (patch)
tree9235f2f0f8b6d839cffc3250ab44ea5a26e0770a /drivers/cpuidle
parent41204a607679ccca7eabff9f2871b969d6ef2ce3 (diff)
downloadlinux-f9901f64536c39f699e6ed228c5e64e7e7ce8708.tar.xz
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')
-rw-r--r--drivers/cpuidle/Kconfig.arm8
-rw-r--r--drivers/cpuidle/cpuidle-psci-domain.c7
-rw-r--r--drivers/cpuidle/cpuidle-psci.c3
3 files changed, 16 insertions, 2 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
diff --git a/drivers/cpuidle/cpuidle-psci-domain.c b/drivers/cpuidle/cpuidle-psci-domain.c
index c80cf9ddabd8..6ad2954948a5 100644
--- a/drivers/cpuidle/cpuidle-psci-domain.c
+++ b/drivers/cpuidle/cpuidle-psci-domain.c
@@ -64,8 +64,11 @@ static int psci_pd_init(struct device_node *np, bool use_osi)
pd->flags |= GENPD_FLAG_IRQ_SAFE | GENPD_FLAG_CPU_DOMAIN;
- /* Allow power off when OSI has been successfully enabled. */
- if (use_osi)
+ /*
+ * Allow power off when OSI has been successfully enabled.
+ * PREEMPT_RT is not yet ready to enter domain idle states.
+ */
+ if (use_osi && !IS_ENABLED(CONFIG_PREEMPT_RT))
pd->power_off = psci_pd_power_off;
else
pd->flags |= GENPD_FLAG_ALWAYS_ON;
diff --git a/drivers/cpuidle/cpuidle-psci.c b/drivers/cpuidle/cpuidle-psci.c
index 57bc3e3ae391..68467a325dcb 100644
--- a/drivers/cpuidle/cpuidle-psci.c
+++ b/drivers/cpuidle/cpuidle-psci.c
@@ -231,6 +231,9 @@ static int psci_dt_cpu_init_topology(struct cpuidle_driver *drv,
if (!psci_has_osi_support())
return 0;
+ if (IS_ENABLED(CONFIG_PREEMPT_RT))
+ return 0;
+
data->dev = psci_dt_attach_cpu(cpu);
if (IS_ERR_OR_NULL(data->dev))
return PTR_ERR_OR_ZERO(data->dev);