d1ff4b1cdb
ACPI 5.0 adds the BGRT, a table that contains a pointer to the firmware boot splash and associated metadata. This simple driver exposes it via /sys/firmware/acpi in order to allow bootsplash applications to draw their splash around the firmware image and reduce the number of jarring graphical transitions during boot. Signed-off-by: Matthew Garrett <mjg@redhat.com> Signed-off-by: Len Brown <len.brown@intel.com>
170 lines
5 KiB
Text
170 lines
5 KiB
Text
What: /sys/firmware/acpi/bgrt/
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Date: January 2012
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Contact: Matthew Garrett <mjg@redhat.com>
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Description:
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The BGRT is an ACPI 5.0 feature that allows the OS
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to obtain a copy of the firmware boot splash and
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some associated metadata. This is intended to be used
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by boot splash applications in order to interact with
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the firmware boot splash in order to avoid jarring
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transitions.
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image: The image bitmap. Currently a 32-bit BMP.
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status: 1 if the image is valid, 0 if firmware invalidated it.
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type: 0 indicates image is in BMP format.
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version: The version of the BGRT. Currently 1.
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xoffset: The number of pixels between the left of the screen
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and the left edge of the image.
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yoffset: The number of pixels between the top of the screen
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and the top edge of the image.
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What: /sys/firmware/acpi/interrupts/
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Date: February 2008
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Contact: Len Brown <lenb@kernel.org>
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Description:
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All ACPI interrupts are handled via a single IRQ,
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the System Control Interrupt (SCI), which appears
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as "acpi" in /proc/interrupts.
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However, one of the main functions of ACPI is to make
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the platform understand random hardware without
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special driver support. So while the SCI handles a few
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well known (fixed feature) interrupts sources, such
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as the power button, it can also handle a variable
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number of a "General Purpose Events" (GPE).
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A GPE vectors to a specified handler in AML, which
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can do a anything the BIOS writer wants from
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OS context. GPE 0x12, for example, would vector
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to a level or edge handler called _L12 or _E12.
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The handler may do its business and return.
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Or the handler may send send a Notify event
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to a Linux device driver registered on an ACPI device,
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such as a battery, or a processor.
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To figure out where all the SCI's are coming from,
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/sys/firmware/acpi/interrupts contains a file listing
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every possible source, and the count of how many
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times it has triggered.
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$ cd /sys/firmware/acpi/interrupts
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$ grep . *
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error: 0
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ff_gbl_lock: 0 enable
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ff_pmtimer: 0 invalid
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ff_pwr_btn: 0 enable
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ff_rt_clk: 2 disable
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ff_slp_btn: 0 invalid
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gpe00: 0 invalid
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gpe01: 0 enable
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gpe02: 108 enable
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gpe03: 0 invalid
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gpe04: 0 invalid
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gpe05: 0 invalid
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gpe06: 0 enable
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gpe07: 0 enable
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gpe08: 0 invalid
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gpe09: 0 invalid
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gpe0A: 0 invalid
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gpe0B: 0 invalid
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gpe0C: 0 invalid
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gpe0D: 0 invalid
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gpe0E: 0 invalid
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gpe0F: 0 invalid
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gpe10: 0 invalid
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gpe11: 0 invalid
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gpe12: 0 invalid
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gpe13: 0 invalid
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gpe14: 0 invalid
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gpe15: 0 invalid
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gpe16: 0 invalid
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gpe17: 1084 enable
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gpe18: 0 enable
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gpe19: 0 invalid
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gpe1A: 0 invalid
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gpe1B: 0 invalid
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gpe1C: 0 invalid
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gpe1D: 0 invalid
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gpe1E: 0 invalid
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gpe1F: 0 invalid
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gpe_all: 1192
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sci: 1194
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sci_not: 0
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sci - The number of times the ACPI SCI
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has been called and claimed an interrupt.
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sci_not - The number of times the ACPI SCI
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has been called and NOT claimed an interrupt.
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gpe_all - count of SCI caused by GPEs.
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gpeXX - count for individual GPE source
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ff_gbl_lock - Global Lock
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ff_pmtimer - PM Timer
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ff_pwr_btn - Power Button
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ff_rt_clk - Real Time Clock
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ff_slp_btn - Sleep Button
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error - an interrupt that can't be accounted for above.
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invalid: it's either a GPE or a Fixed Event that
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doesn't have an event handler.
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disable: the GPE/Fixed Event is valid but disabled.
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enable: the GPE/Fixed Event is valid and enabled.
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Root has permission to clear any of these counters. Eg.
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# echo 0 > gpe11
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All counters can be cleared by clearing the total "sci":
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# echo 0 > sci
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None of these counters has an effect on the function
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of the system, they are simply statistics.
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Besides this, user can also write specific strings to these files
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to enable/disable/clear ACPI interrupts in user space, which can be
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used to debug some ACPI interrupt storm issues.
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Note that only writting to VALID GPE/Fixed Event is allowed,
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i.e. user can only change the status of runtime GPE and
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Fixed Event with event handler installed.
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Let's take power button fixed event for example, please kill acpid
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and other user space applications so that the machine won't shutdown
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when pressing the power button.
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# cat ff_pwr_btn
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0 enabled
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# press the power button for 3 times;
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# cat ff_pwr_btn
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3 enabled
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# echo disable > ff_pwr_btn
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# cat ff_pwr_btn
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3 disabled
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# press the power button for 3 times;
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# cat ff_pwr_btn
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3 disabled
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# echo enable > ff_pwr_btn
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# cat ff_pwr_btn
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4 enabled
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/*
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* this is because the status bit is set even if the enable bit is cleared,
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* and it triggers an ACPI fixed event when the enable bit is set again
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*/
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# press the power button for 3 times;
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# cat ff_pwr_btn
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7 enabled
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# echo disable > ff_pwr_btn
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# press the power button for 3 times;
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# echo clear > ff_pwr_btn /* clear the status bit */
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# echo disable > ff_pwr_btn
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# cat ff_pwr_btn
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7 enabled
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