| What: /sys/firmware/acpi/interrupts/ |
| Date: February 2008 |
| Contact: Len Brown <lenb@kernel.org> |
| 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 |
| |
