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authorKeerthy <j-keerthy@ti.com>2017-04-18 09:59:59 +0530
committerZhang Rui <rui.zhang@intel.com>2017-05-05 16:01:45 +0800
commitef1d87e06ab4d3f9a95f02517ecc50902dc233a7 (patch)
tree6dd3327394c0cb14fa964a3a8baf1c51b6d0e337 /Documentation/thermal
parente441fd68663e298e99a99e215e0144a0eda6250d (diff)
thermal: core: Add a back up thermal shutdown mechanism
orderly_poweroff is triggered when a graceful shutdown of system is desired. This may be used in many critical states of the kernel such as when subsystems detects conditions such as critical temperature conditions. However, in certain conditions in system boot up sequences like those in the middle of driver probes being initiated, userspace will be unable to power off the system in a clean manner and leaves the system in a critical state. In cases like these, the /sbin/poweroff will return success (having forked off to attempt powering off the system. However, the system overall will fail to completely poweroff (since other modules will be probed) and the system is still functional with no userspace (since that would have shut itself off). However, there is no clean way of detecting such failure of userspace powering off the system. In such scenarios, it is necessary for a backup workqueue to be able to force a shutdown of the system when orderly shutdown is not successful after a configurable time period. Reported-by: Nishanth Menon <nm@ti.com> Signed-off-by: Keerthy <j-keerthy@ti.com> Acked-by: Eduardo Valentin <edubezval@gmail.com> Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Diffstat (limited to 'Documentation/thermal')
-rw-r--r--Documentation/thermal/sysfs-api.txt21
1 files changed, 21 insertions, 0 deletions
diff --git a/Documentation/thermal/sysfs-api.txt b/Documentation/thermal/sysfs-api.txt
index ef473dc7f55e..bb9a0a53e76b 100644
--- a/Documentation/thermal/sysfs-api.txt
+++ b/Documentation/thermal/sysfs-api.txt
@@ -582,3 +582,24 @@ platform data is provided, this uses the step_wise throttling policy.
This function serves as an arbitrator to set the state of a cooling
device. It sets the cooling device to the deepest cooling state if
possible.
+
+6. thermal_emergency_poweroff:
+
+On an event of critical trip temperature crossing. Thermal framework
+allows the system to shutdown gracefully by calling orderly_poweroff().
+In the event of a failure of orderly_poweroff() to shut down the system
+we are in danger of keeping the system alive at undesirably high
+temperatures. To mitigate this high risk scenario we program a work
+queue to fire after a pre-determined number of seconds to start
+an emergency shutdown of the device using the kernel_power_off()
+function. In case kernel_power_off() fails then finally
+emergency_restart() is called in the worst case.
+
+The delay should be carefully profiled so as to give adequate time for
+orderly_poweroff(). In case of failure of an orderly_poweroff() the
+emergency poweroff kicks in after the delay has elapsed and shuts down
+the system.
+
+If set to 0 emergency poweroff will not be supported. So a carefully
+profiled non-zero positive value is a must for emergerncy poweroff to be
+triggered.