diff options
| author | Ulf Hansson <ulf.hansson@linaro.org> | 2025-11-25 12:26:47 +0100 |
|---|---|---|
| committer | Rafael J. Wysocki <rafael.j.wysocki@intel.com> | 2025-11-25 19:01:30 +0100 |
| commit | c19dfb267c28032293515a635eaefbf9194629ac (patch) | |
| tree | 0393702691e34d82424be375f6fefaf1d4378b7f | |
| parent | 2b8d594742398cdbf40012c0b3c8b71ca160e22d (diff) | |
Documentation: power/cpuidle: Document the CPU system wakeup latency QoS
Let's document how the new CPU system wakeup latency QoS limit can be used
from user space, along with how the constraint is taken into account for
s2idle and cpuidle.
Reviewed-by: Dhruva Gole <d-gole@ti.com>
Reviewed-by: Kevin Hilman (TI) <khilman@baylibre.com>
Tested-by: Kevin Hilman (TI) <khilman@baylibre.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Link: https://patch.msgid.link/20251125112650.329269-7-ulf.hansson@linaro.org
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
| -rw-r--r-- | Documentation/admin-guide/pm/cpuidle.rst | 9 | ||||
| -rw-r--r-- | Documentation/power/pm_qos_interface.rst | 9 |
2 files changed, 14 insertions, 4 deletions
diff --git a/Documentation/admin-guide/pm/cpuidle.rst b/Documentation/admin-guide/pm/cpuidle.rst index 0c090b076224..be4c1120e3f0 100644 --- a/Documentation/admin-guide/pm/cpuidle.rst +++ b/Documentation/admin-guide/pm/cpuidle.rst @@ -580,6 +580,15 @@ the given CPU as the upper limit for the exit latency of the idle states that they are allowed to select for that CPU. They should never select any idle states with exit latency beyond that limit. +While the above CPU QoS constraints apply to CPU idle time management, user +space may also request a CPU system wakeup latency QoS limit, via the +`cpu_wakeup_latency` file. This QoS constraint is respected when selecting a +suitable idle state for the CPUs, while entering the system-wide suspend-to-idle +sleep state, but also to the regular CPU idle time management. + +Note that, the management of the `cpu_wakeup_latency` file works according to +the 'cpu_dma_latency' file from user space point of view. Moreover, the unit +is also microseconds. Idle States Control Via Kernel Command Line =========================================== diff --git a/Documentation/power/pm_qos_interface.rst b/Documentation/power/pm_qos_interface.rst index 5019c79c7710..4c008e2202f0 100644 --- a/Documentation/power/pm_qos_interface.rst +++ b/Documentation/power/pm_qos_interface.rst @@ -55,7 +55,8 @@ int cpu_latency_qos_request_active(handle): From user space: -The infrastructure exposes one device node, /dev/cpu_dma_latency, for the CPU +The infrastructure exposes two separate device nodes, /dev/cpu_dma_latency for +the CPU latency QoS and /dev/cpu_wakeup_latency for the CPU system wakeup latency QoS. Only processes can register a PM QoS request. To provide for automatic @@ -63,15 +64,15 @@ cleanup of a process, the interface requires the process to register its parameter requests as follows. To register the default PM QoS target for the CPU latency QoS, the process must -open /dev/cpu_dma_latency. +open /dev/cpu_dma_latency. To register a CPU system wakeup QoS limit, the +process must open /dev/cpu_wakeup_latency. As long as the device node is held open that process has a registered request on the parameter. To change the requested target value, the process needs to write an s32 value to the open device node. Alternatively, it can write a hex string for the value -using the 10 char long format e.g. "0x12345678". This translates to a -cpu_latency_qos_update_request() call. +using the 10 char long format e.g. "0x12345678". To remove the user mode request for a target value simply close the device node. |