[coreboot-gerrit] Change in coreboot[master]: src: Never set ISA Enable on PCI bridges

[Patrick Rudolph (Code Review)]

Patrick Rudolph has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/43775 )

Change subject: src: Never set ISA Enable on PCI bridges
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Patch Set 1: Code-Review+2

This might even conflict with bridge I/O resources assigned by the PCI allocator.

The best source for ISA I could find is the book "EISA System Architecture" by Tom Shanley. See chapter "ISA I/O Address Space Problem". Setting the bit makes sure that the address pins A[9:8] on the ISA bus can never be > 0. That adds support for ISA devices only decoding 8bit addresses. As we cannot detect such ISA devices/slots that should be a devicetree option or part of the mainboard code. I doubt it's useful on recent PCIe based platforms.