===Software thermal protection ===
In DESK-MX8-L, two software thermal protection mechanisms are implemented. Both are based on the processor's temperature sensor. It is worth remembering that maximum junction temperature (also denoted as Tj in the rest of the document) is:
*95°C for commercial parts*105°C for extended commercial and industrial parts*125°C for automotive parts. ={| style===U-Boot====At U-Boot level, automatic boot procedure is halted until Tj is smaller than (following temperatures might seem excessively low but they take into account the intrinsic poor precision of the temperature sensor to provide a reasonable safe margin)"color: *80°C for commercial parts*90 for extended commercial and industrial parts*110°C for automotive parts. ====Linux kernel====At Linux level, a more sophisticated protection mechanism is implemented. Please refer to the following sections for more details. The default temperature thresholds depend on the silicon grade, as follows#000000; border: *for commercial parts** passive thresholdsolid 2px #73B2C7; background-color: 85°C** critical threshold#ededed;font-size: 90°C*for extended commercial and industrial parts** passive threshold95%; vertical-align: 95°Cmiddle;"** critical threshold|[[File: 100°C*for automotive parts** passive threshold: 115°C** critical threshold: 120°CTBD.png|30px]] Practically speaking, for DESK-MX8-L this mechanism makes use of two different thresholds, denoted as <code>trip_point0</code> (also known as ''passive threshold|'') and <code>trip_point1</code> (also known as 'Section not completed yet'critical threshold''. When Tj reaches <code>trip_point0</code>, Linux kernel scales down processor frequency: <pre>System is too hot. GPU3D will work at 1/64 clock.</pre> If Tj reaches <code>trip_point1</code>, a complete shutdown is triggered: <pre>thermal thermal_zone0: critical temperature reached(100 C),shutting down</pre> By default, temperature thresholds are set up as follows:*<code>trip_point0</code>: 85°C*<code>trip_point1</code>: 100°C. Trip point thresholds can be accessed via <code>sysfs</code> interface from user space. The following example shows how to read the values of the trip points:<pre>root@axel-lite:~# cat /sys/devices/virtual/thermal/thermal_zone0/trip_point_0_temp85000root@axel-lite:~# cat /sys/devices/virtual/thermal/thermal_zone0/trip_point_1_temp100000</pre>This example shows how to set trip points 0 and 1 to 95°C and 100°C respectively:<pre>echo 95000 > /sys/class/thermal/thermal_zone0/trip_point_0_tempecho 100000 > /sys/class/thermal/thermal_zone0/trip_point_1_temp</pre>{{ImportantMessage|text=Please note that*it is possible to set up trip points greater than the maximum junction temperature indicated by manufacturer datasheet*exceeding maximum junction temperature indicated by manufacturer datasheet may cause permanent damage}} To read current processor temperature please issue this command (reported temperature is 36.676°C in the example): <pre>root@axel-lite:~# cat /sys/class/thermal/thermal_zone0/temp36676</pre> For more details about this functionality, please refer to <code>Documentation/thermal/sysfs-api.txt</code> in the kernel sources.
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[[Category:ORCA]]
