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The LS1021A allows inverting the polarity of six interrupt lines IRQ[0:5] via the scfg_intpcr register, effectively allowing IRQ_TYPE_LEVEL_LOW and IRQ_TYPE_EDGE_FALLING for those. We just need to check the type, set the relevant bit in INTPCR accordingly, and fixup the type argument before calling the GIC's irq_set_type. In fact, the power-on-reset value of the INTPCR register on the LS1021A is so that all six lines have their polarity inverted. Hence any hardware connected to those lines is unusable without this: If the line is indeed active low, the generic GIC code will reject an irq spec with IRQ_TYPE_LEVEL_LOW, while if the line is active high, we must obviously disable the polarity inversion (writing 0 to the relevant bit) before unmasking the interrupt. Some other Layerscape SOCs (LS1043A, LS1046A) have a similar feature, just with a different number of external interrupt lines (and a different POR value for the INTPCR register). This driver should be prepared for supporting those by properly filling out the device tree node. I have the reference manuals for all three boards, but I've only tested the driver on an LS1021A. Unfortunately, the Kconfig symbol ARCH_LAYERSCAPE only exists on arm64, so do as is done for irq-ls-scfg-msi.c: introduce a new symbol which is set when either ARCH_LAYERSCAPE or SOC_LS1021A is set. Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk> Signed-off-by: Marc Zyngier <maz@kernel.org> Link: https://lore.kernel.org/r/20191107122115.6244-3-linux@rasmusvillemoes.dk
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.