63 lines
2.0 KiB
Plaintext
63 lines
2.0 KiB
Plaintext
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Userspace thermal alert
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=======================
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Provides the facility for user space to know whether a thermal alert
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occurred or not for temperature trip value. This is Supported by adding
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a software thermal cooling device.
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Features
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--------
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- Sends an "uevent" notification to user space on tripping the associated
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thermal trip point.
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"uevent" comes under /sys/class/thermal/cooling_device[0-*].
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- sysfs API:
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sysfs attributes are represented under
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/sys/bus/platform/devices/userspace-alert.
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Also a symlink to this is provide with
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/sys/class/thermal/cooling_device[0-*]/userspace_alert.
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/sys/bus/platform/devices/userspace-alert:
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/sys/class/thermal/cooling_device[0-*]/userspace_alert:
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|---thermal_alert_block
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|---thermal_alert
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thermal_alert_block
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Read/Write value
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Read: Blocks the read call until an alert occurs or the
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specified duration times out. When alert occurs or if
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alert is already present then read returns immediately
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with value "1". If alert is not there and time out
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happens then read returns with value "0".
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Write: Set the time out duration(in milli seconds) to
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wait when alert is not present. By default this value is
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"0" if not set. Value of "0" wall wait for infinite
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time. When alert occurs or if alert is already present,
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then write value has no significance.
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thermal_alert
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Read only value
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Read: If alert is present returns "1", otherwise
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returns "0".
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- The trip temperature can be modified at runtime if writable permission is
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set in device tree properties of trip temperature.
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If alert occurs then by increasing the trip temperature to value greater than
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current temperature will make the alert to go off and user space can wait for
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alert again with increased temperature trip.
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For trip temperature sysfs, refer Documentation/thermal/sysfs-api.txt.
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Note:
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-----
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This cooling device is intended with single trip temperature. When associated
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with multiple trip points, alert will come for every trip temperature except
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for the case when temperature goes to lower than the lowest trip temperature.
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