From 4f3549d72d1b5c90ecc7e673402f38f4486d22c2 Mon Sep 17 00:00:00 2001 From: "Rafael J. Wysocki" Date: Thu, 2 May 2013 22:15:29 +0200 Subject: Driver core: Add offline/online device operations In some cases, graceful hot-removal of devices is not possible, although in principle the devices in question support hotplug. For example, that may happen for the last CPU in the system or for memory modules holding kernel memory. In those cases it is nice to be able to check if the given device can be gracefully hot-removed before triggering a removal procedure that cannot be aborted or reversed. Unfortunately, however, the kernel currently doesn't provide any support for that. To address that deficiency, introduce support for offline and online operations that can be performed on devices, respectively, before a hot-removal and in case when it is necessary (or convenient) to put a device back online after a successful offline (that has not been followed by removal). The idea is that the offline will fail whenever the given device cannot be gracefully removed from the system and it will not be allowed to use the device after a successful offline (until a subsequent online) in analogy with the existing CPU offline/online mechanism. For now, the offline and online operations are introduced at the bus type level, as that should be sufficient for the most urgent use cases (CPUs and memory modules). In the future, however, the approach may be extended to cover some more complicated device offline/online scenarios involving device drivers etc. The lock_device_hotplug() and unlock_device_hotplug() functions are introduced because subsequent patches need to put larger pieces of code under device_hotplug_lock to prevent race conditions between device offline and removal from happening. Signed-off-by: Rafael J. Wysocki Acked-by: Greg Kroah-Hartman Reviewed-by: Toshi Kani --- Documentation/ABI/testing/sysfs-devices-online | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) create mode 100644 Documentation/ABI/testing/sysfs-devices-online (limited to 'Documentation/ABI') diff --git a/Documentation/ABI/testing/sysfs-devices-online b/Documentation/ABI/testing/sysfs-devices-online new file mode 100644 index 000000000000..f990026c0740 --- /dev/null +++ b/Documentation/ABI/testing/sysfs-devices-online @@ -0,0 +1,20 @@ +What: /sys/devices/.../online +Date: April 2013 +Contact: Rafael J. Wysocki +Description: + The /sys/devices/.../online attribute is only present for + devices whose bus types provide .online() and .offline() + callbacks. The number read from it (0 or 1) reflects the value + of the device's 'offline' field. If that number is 1 and '0' + (or 'n', or 'N') is written to this file, the device bus type's + .offline() callback is executed for the device and (if + successful) its 'offline' field is updated accordingly. In + turn, if that number is 0 and '1' (or 'y', or 'Y') is written to + this file, the device bus type's .online() callback is executed + for the device and (if successful) its 'offline' field is + updated as appropriate. + + After a successful execution of the bus type's .offline() + callback the device cannot be used for any purpose until either + it is removed (i.e. device_del() is called for it), or its bus + type's .online() is exeucted successfully. -- cgit v1.2.3 From 683058e315f00a216fd6c79df4f63bc9945ca434 Mon Sep 17 00:00:00 2001 From: "Rafael J. Wysocki" Date: Fri, 3 May 2013 00:26:16 +0200 Subject: ACPI / hotplug: Use device offline/online for graceful hot-removal Modify the generic ACPI hotplug code to be able to check if devices scheduled for hot-removal may be gracefully removed from the system using the device offline/online mechanism introduced previously. Namely, make acpi_scan_hot_remove() handling device hot-removal call device_offline() for all physical companions of the ACPI device nodes involved in the operation and check the results. If any of the device_offline() calls fails, the function will not progress to the removal phase (which cannot be aborted), unless its (new) force argument is set (in case of a failing offline it will put the devices offlined by it back online). In support of 'forced' device hot-removal, add a new sysfs attribute 'force_remove' that will reside under /sys/firmware/acpi/hotplug/. Signed-off-by: Rafael J. Wysocki Reviewed-by: Toshi Kani --- Documentation/ABI/testing/sysfs-firmware-acpi | 10 ++++++++++ 1 file changed, 10 insertions(+) (limited to 'Documentation/ABI') diff --git a/Documentation/ABI/testing/sysfs-firmware-acpi b/Documentation/ABI/testing/sysfs-firmware-acpi index ce9bee98b43b..b4436cca97a8 100644 --- a/Documentation/ABI/testing/sysfs-firmware-acpi +++ b/Documentation/ABI/testing/sysfs-firmware-acpi @@ -44,6 +44,16 @@ Description: or 0 (unset). Attempts to write any other values to it will cause -EINVAL to be returned. +What: /sys/firmware/acpi/hotplug/force_remove +Date: May 2013 +Contact: Rafael J. Wysocki +Description: + The number in this file (0 or 1) determines whether (1) or not + (0) the ACPI subsystem will allow devices to be hot-removed even + if they cannot be put offline gracefully (from the kernel's + viewpoint). That number can be changed by writing a boolean + value to this file. + What: /sys/firmware/acpi/interrupts/ Date: February 2008 Contact: Len Brown -- cgit v1.2.3 From de9c739435b47e7d39e448b2cc4c8154cabc9e5a Mon Sep 17 00:00:00 2001 From: MyungJoo Ham Date: Tue, 5 Feb 2013 18:40:17 +0900 Subject: PM / devfreq: add comments and Documentation - Added missing ABI documents - Added comments to clarify the objectives of functions Signed-off-by: MyungJoo Ham Acked-by: Nishanth Menon Acked-by: Rajagopal Venkat --- Documentation/ABI/testing/sysfs-class-devfreq | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) (limited to 'Documentation/ABI') diff --git a/Documentation/ABI/testing/sysfs-class-devfreq b/Documentation/ABI/testing/sysfs-class-devfreq index 0ba6ea2f89d9..ee39acacf6f8 100644 --- a/Documentation/ABI/testing/sysfs-class-devfreq +++ b/Documentation/ABI/testing/sysfs-class-devfreq @@ -78,3 +78,23 @@ Contact: Nishanth Menon Description: The /sys/class/devfreq/.../available_governors shows currently available governors in the system. + +What: /sys/class/devfreq/.../min_freq +Date: January 2013 +Contact: MyungJoo Ham +Description: + The /sys/class/devfreq/.../min_freq shows and stores + the minimum frequency requested by users. It is 0 if + the user does not care. min_freq overrides the + frequency requested by governors. + +What: /sys/class/devfreq/.../max_freq +Date: January 2013 +Contact: MyungJoo Ham +Description: + The /sys/class/devfreq/.../max_freq shows and stores + the maximum frequency requested by users. It is 0 if + the user does not care. max_freq overrides the + frequency requested by governors and min_freq. + The max_freq overrides min_freq because max_freq may be + used to throttle devices to avoid overheating. -- cgit v1.2.3 From 89ca78a060a101b21cec46f34ad2ade3fafed0d0 Mon Sep 17 00:00:00 2001 From: Lv Zheng Date: Thu, 20 Jun 2013 08:02:44 +0800 Subject: ACPI: Add sysfs ABI documentation Add initial ABI documentation for ACPI devices' sysfs interfaces. Contacts information fields are filled with current ACPI maintainer and the relevant authors are carbon copied. [rjw: Use my e-mail address that's likely to be valid longer.] Signed-off-by: Lv Zheng Signed-off-by: Rafael J. Wysocki --- Documentation/ABI/testing/sysfs-bus-acpi | 58 +++++++++++++++++++++++++++++ Documentation/ABI/testing/sysfs-devices-sun | 2 +- 2 files changed, 59 insertions(+), 1 deletion(-) create mode 100644 Documentation/ABI/testing/sysfs-bus-acpi (limited to 'Documentation/ABI') diff --git a/Documentation/ABI/testing/sysfs-bus-acpi b/Documentation/ABI/testing/sysfs-bus-acpi new file mode 100644 index 000000000000..7fa9cbc75344 --- /dev/null +++ b/Documentation/ABI/testing/sysfs-bus-acpi @@ -0,0 +1,58 @@ +What: /sys/bus/acpi/devices/.../path +Date: December 2006 +Contact: Rafael J. Wysocki +Description: + This attribute indicates the full path of ACPI namespace + object associated with the device object. For example, + \_SB_.PCI0. + This file is not present for device objects representing + fixed ACPI hardware features (like power and sleep + buttons). + +What: /sys/bus/acpi/devices/.../modalias +Date: July 2007 +Contact: Rafael J. Wysocki +Description: + This attribute indicates the PNP IDs of the device object. + That is acpi:HHHHHHHH:[CCCCCCC:]. Where each HHHHHHHH or + CCCCCCCC contains device object's PNPID (_HID or _CID). + +What: /sys/bus/acpi/devices/.../hid +Date: April 2005 +Contact: Rafael J. Wysocki +Description: + This attribute indicates the hardware ID (_HID) of the + device object. For example, PNP0103. + This file is present for device objects having the _HID + control method. + +What: /sys/bus/acpi/devices/.../description +Date: October 2012 +Contact: Rafael J. Wysocki +Description: + This attribute contains the output of the device object's + _STR control method, if present. + +What: /sys/bus/acpi/devices/.../adr +Date: October 2012 +Contact: Rafael J. Wysocki +Description: + This attribute contains the output of the device object's + _ADR control method, which is present for ACPI device + objects representing devices having standard enumeration + algorithms, such as PCI. + +What: /sys/bus/acpi/devices/.../uid +Date: October 2012 +Contact: Rafael J. Wysocki +Description: + This attribute contains the output of the device object's + _UID control method, if present. + +What: /sys/bus/acpi/devices/.../eject +Date: December 2006 +Contact: Rafael J. Wysocki +Description: + Writing 1 to this attribute will trigger hot removal of + this device object. This file exists for every device + object that has _EJ0 method. diff --git a/Documentation/ABI/testing/sysfs-devices-sun b/Documentation/ABI/testing/sysfs-devices-sun index 86be9848a77e..625ce4b63758 100644 --- a/Documentation/ABI/testing/sysfs-devices-sun +++ b/Documentation/ABI/testing/sysfs-devices-sun @@ -1,4 +1,4 @@ -Whatt: /sys/devices/.../sun +What: /sys/devices/.../sun Date: October 2012 Contact: Yasuaki Ishimatsu Description: -- cgit v1.2.3 From f4fd3797848aa04e72e942c855fd279840a47fe4 Mon Sep 17 00:00:00 2001 From: Lan Tianyu Date: Thu, 27 Jun 2013 15:08:54 +0800 Subject: acpi-cpufreq: Add new sysfs attribute freqdomain_cpus Commits fcf8058 (cpufreq: Simplify cpufreq_add_dev()) and aa77a52 (cpufreq: acpi-cpufreq: Don't set policy->related_cpus from .init()) changed the contents of the "related_cpus" sysfs attribute on systems where acpi-cpufreq is used and user space can't get the list of CPUs which are in the same hardware coordination CPU domain (provided by the ACPI AML method _PSD) via "related_cpus" any more. To make up for that loss add a new sysfs attribute "freqdomian_cpus" for the acpi-cpufreq driver which exposes the list of CPUs in the same domain regardless of whether it is coordinated by hardware or software. [rjw: Changelog, documentation] References: https://bugzilla.kernel.org/show_bug.cgi?id=58761 Reported-by: Jean-Philippe Halimi Signed-off-by: Lan Tianyu Acked-by: Viresh Kumar Signed-off-by: Rafael J. Wysocki --- Documentation/ABI/testing/sysfs-devices-system-cpu | 15 +++++++++++++++ 1 file changed, 15 insertions(+) (limited to 'Documentation/ABI') diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu index 2447698aed41..468e4d48f884 100644 --- a/Documentation/ABI/testing/sysfs-devices-system-cpu +++ b/Documentation/ABI/testing/sysfs-devices-system-cpu @@ -144,6 +144,21 @@ Description: Discover and change clock speed of CPUs to learn how to control the knobs. +What: /sys/devices/system/cpu/cpu#/cpufreq/freqdomain_cpus +Date: June 2013 +Contact: cpufreq@vger.kernel.org +Description: Discover CPUs in the same CPU frequency coordination domain + + freqdomain_cpus is the list of CPUs (online+offline) that share + the same clock/freq domain (possibly at the hardware level). + That information may be hidden from the cpufreq core and the + value of related_cpus may be different from freqdomain_cpus. This + attribute is useful for user space DVFS controllers to get better + power/performance results for platforms using acpi-cpufreq. + + This file is only present if the acpi-cpufreq driver is in use. + + What: /sys/devices/system/cpu/cpu*/cache/index3/cache_disable_{0,1} Date: August 2008 KernelVersion: 2.6.27 -- cgit v1.2.3