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authorAnton Arapov <anton@redhat.com>2012-04-16 10:05:28 +0200
committerAnton Arapov <anton@redhat.com>2012-04-16 10:05:28 +0200
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fedora kernel: d9aad82f3319f3cfd1aebc01234254ef0c37ad84v3.3.2-1
Signed-off-by: Anton Arapov <anton@redhat.com>
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+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
+