diff options
Diffstat (limited to 'Documentation/power')
| -rw-r--r-- | Documentation/power/index.rst | 1 | ||||
| -rw-r--r-- | Documentation/power/pm_qos_interface.rst | 9 | ||||
| -rw-r--r-- | Documentation/power/runtime_pm.rst | 10 | ||||
| -rw-r--r-- | Documentation/power/shutdown-debugging.rst | 53 |
4 files changed, 59 insertions, 14 deletions
diff --git a/Documentation/power/index.rst b/Documentation/power/index.rst index a0f5244fb427..ea70633d9ce6 100644 --- a/Documentation/power/index.rst +++ b/Documentation/power/index.rst @@ -19,6 +19,7 @@ Power Management power_supply_class runtime_pm s2ram + shutdown-debugging suspend-and-cpuhotplug suspend-and-interrupts swsusp-and-swap-files 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. diff --git a/Documentation/power/runtime_pm.rst b/Documentation/power/runtime_pm.rst index c8dbdb8595e5..8246df3cecd7 100644 --- a/Documentation/power/runtime_pm.rst +++ b/Documentation/power/runtime_pm.rst @@ -480,16 +480,6 @@ drivers/base/power/runtime.c and include/linux/pm_runtime.h: `bool pm_runtime_status_suspended(struct device *dev);` - return true if the device's runtime PM status is 'suspended' - `void pm_runtime_allow(struct device *dev);` - - set the power.runtime_auto flag for the device and decrease its usage - counter (used by the /sys/devices/.../power/control interface to - effectively allow the device to be power managed at run time) - - `void pm_runtime_forbid(struct device *dev);` - - unset the power.runtime_auto flag for the device and increase its usage - counter (used by the /sys/devices/.../power/control interface to - effectively prevent the device from being power managed at run time) - `void pm_runtime_no_callbacks(struct device *dev);` - set the power.no_callbacks flag for the device and remove the runtime PM attributes from /sys/devices/.../power (or prevent them from being diff --git a/Documentation/power/shutdown-debugging.rst b/Documentation/power/shutdown-debugging.rst new file mode 100644 index 000000000000..c510122e0bbc --- /dev/null +++ b/Documentation/power/shutdown-debugging.rst @@ -0,0 +1,53 @@ +.. SPDX-License-Identifier: GPL-2.0 + +Debugging Kernel Shutdown Hangs with pstore ++++++++++++++++++++++++++++++++++++++++++++ + +Overview +======== +If the system hangs while shutting down, the kernel logs may need to be +retrieved to debug the issue. + +On systems that have a UART available, it is best to configure the kernel to use +this UART for kernel console output. + +If a UART isn't available, the ``pstore`` subsystem provides a mechanism to +persist this data across a system reset, allowing it to be retrieved on the next +boot. + +Kernel Configuration +==================== +To enable ``pstore`` and enable saving kernel ring buffer logs, set the +following kernel configuration options: + +* ``CONFIG_PSTORE=y`` +* ``CONFIG_PSTORE_CONSOLE=y`` + +Additionally, enable a backend to store the data. Depending upon your platform +some potential options include: + +* ``CONFIG_EFI_VARS_PSTORE=y`` +* ``CONFIG_PSTORE_RAM=y`` +* ``CONFIG_CHROMEOS_PSTORE=y`` +* ``CONFIG_PSTORE_BLK=y`` + +Kernel Command-line Parameters +============================== +Add these parameters to your kernel command line: + +* ``printk.always_kmsg_dump=Y`` + * Forces the kernel to dump the entire message buffer to pstore during + shutdown +* ``efi_pstore.pstore_disable=N`` + * For EFI-based systems, ensures the EFI backend is active + +Userspace Interaction and Log Retrieval +======================================= +On the next boot after a hang, pstore logs will be available in the pstore +filesystem (``/sys/fs/pstore``) and can be retrieved by userspace. + +On systemd systems, the ``systemd-pstore`` service will help do the following: + +#. Locate pstore data in ``/sys/fs/pstore`` +#. Read and save it to ``/var/lib/systemd/pstore`` +#. Clear pstore data for the next event |