What: /sys/firmware/acpi/interrupts/ Date: February 2008 Contact: Len Brown Description: All ACPI interrupts are handled via a single IRQ, the System Control Interrupt (SCI), which appears as "acpi" in /proc/interrupts. However, one of the main functions of ACPI is to make the platform understand random hardware without special driver support. So while the SCI handles a few well known (fixed feature) interrupts sources, such as the power button, it can also handle a variable number of a "General Purpose Events" (GPE). A GPE vectors to a specified handler in AML, which can do a anything the BIOS writer wants from OS context. GPE 0x12, for example, would vector to a level or edge handler called _L12 or _E12. The handler may do its business and return. Or the handler may send send a Notify event to a Linux device driver registered on an ACPI device, such as a battery, or a processor. To figure out where all the SCI's are coming from, /sys/firmware/acpi/interrupts contains a file listing every possible source, and the count of how many times it has triggered. $ cd /sys/firmware/acpi/interrupts $ grep . * error: 0 ff_gbl_lock: 0 enable ff_pmtimer: 0 invalid ff_pwr_btn: 0 enable ff_rt_clk: 2 disable ff_slp_btn: 0 invalid gpe00: 0 invalid gpe01: 0 enable gpe02: 108 enable gpe03: 0 invalid gpe04: 0 invalid gpe05: 0 invalid gpe06: 0 enable gpe07: 0 enable gpe08: 0 invalid gpe09: 0 invalid gpe0A: 0 invalid gpe0B: 0 invalid gpe0C: 0 invalid gpe0D: 0 invalid gpe0E: 0 invalid gpe0F: 0 invalid gpe10: 0 invalid gpe11: 0 invalid gpe12: 0 invalid gpe13: 0 invalid gpe14: 0 invalid gpe15: 0 invalid gpe16: 0 invalid gpe17: 1084 enable gpe18: 0 enable gpe19: 0 invalid gpe1A: 0 invalid gpe1B: 0 invalid gpe1C: 0 invalid gpe1D: 0 invalid gpe1E: 0 invalid gpe1F: 0 invalid gpe_all: 1192 sci: 1194 sci_not: 0 sci - The number of times the ACPI SCI has been called and claimed an interrupt. sci_not - The number of times the ACPI SCI has been called and NOT claimed an interrupt. gpe_all - count of SCI caused by GPEs. gpeXX - count for individual GPE source ff_gbl_lock - Global Lock ff_pmtimer - PM Timer ff_pwr_btn - Power Button ff_rt_clk - Real Time Clock ff_slp_btn - Sleep Button error - an interrupt that can't be accounted for above. invalid: it's either a GPE or a Fixed Event that doesn't have an event handler. disable: the GPE/Fixed Event is valid but disabled. enable: the GPE/Fixed Event is valid and enabled. Root has permission to clear any of these counters. Eg. # echo 0 > gpe11 All counters can be cleared by clearing the total "sci": # echo 0 > sci None of these counters has an effect on the function of the system, they are simply statistics. Besides this, user can also write specific strings to these files to enable/disable/clear ACPI interrupts in user space, which can be used to debug some ACPI interrupt storm issues. Note that only writting to VALID GPE/Fixed Event is allowed, i.e. user can only change the status of runtime GPE and Fixed Event with event handler installed. Let's take power button fixed event for example, please kill acpid and other user space applications so that the machine won't shutdown when pressing the power button. # cat ff_pwr_btn 0 enabled # press the power button for 3 times; # cat ff_pwr_btn 3 enabled # echo disable > ff_pwr_btn # cat ff_pwr_btn 3 disabled # press the power button for 3 times; # cat ff_pwr_btn 3 disabled # echo enable > ff_pwr_btn # cat ff_pwr_btn 4 enabled /* * this is because the status bit is set even if the enable bit is cleared, * and it triggers an ACPI fixed event when the enable bit is set again */ # press the power button for 3 times; # cat ff_pwr_btn 7 enabled # echo disable > ff_pwr_btn # press the power button for 3 times; # echo clear > ff_pwr_btn /* clear the status bit */ # echo disable > ff_pwr_btn # cat ff_pwr_btn 7 enabled