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On LoongArch based systems, the PCI devices (e.g. SATA controllers and PCI-to-PCI bridge controllers) in Loongson chipsets output high-level interrupt signal to the interrupt controller they are connected (see Loongson 7A1000 Bridge User Manual v2.00, sec 5.3, "For the bridge chip, AC97 DMA interrupts are edge triggered, gpio interrupts can be configured to be level triggered or edge triggered as needed, and the rest of the interrupts are level triggered and active high."), while the IRQs are active low from the perspective of PCI (see Conventional PCI spec r3.0, sec 2.2.6, "Interrupts on PCI are optional and defined as level sensitive, asserted low."), which means that the interrupt output of PCI devices plugged into PCI-to-PCI bridges of Loongson chipset will be also converted to high-level. So high level triggered type is required to be passed to acpi_register_gsi() when creating mappings for PCI devices. Signed-off-by: Jianmin Lv <lvjianmin@loongson.cn> Reviewed-by: Huacai Chen <chenhuacai@loongson.cn> Signed-off-by: Marc Zyngier <maz@kernel.org> Link: https://lore.kernel.org/r/20221022075955.11726-2-lvjianmin@loongson.cn
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.