[coreboot-gerrit] [M] Change in coreboot[main]: device: Add support for multiple PCI segments

[Patrick Rudolph (Code Review)]

Attention is currently required from: Cliff Huang, Felix Held, Fred Reitberger, Jason Glenesk, Lance Zhao, Matt DeVillier, Nico Huber, Tim Wawrzynczak.

Patrick Rudolph has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/79877?usp=email )

Change subject: device: Add support for multiple PCI segments
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Patch Set 1:

(2 comments)

File src/device/Kconfig:

https://review.coreboot.org/c/coreboot/+/79877/comment/8046d6a4_46124f15 :
PS1, Line 559: config ECAM_SEGMENT_COUNT
> i first also added a kconfig option for this, but ended up removing it again, since just using 512 o […]

My impression was that ECAM_MMCONF_BUS_NUMBER == 256 would be the better choice for the subordinate and max_subordinate handling.

File src/include/device/device.h:

https://review.coreboot.org/c/coreboot/+/79877/comment/863e1fd5_6a6d3190 :
PS1, Line 89: 	uint8_t		segment;		/* PCI segment */
> Nico and i discussed this topic on irc some weeks ago and we ended up with the conclusion that using […]

I'd be happy to test those to not have duplicate effort.

My first try was to use the upper 8 bit of `secondary`, but this was discarded in order to reuse existing code in src/device/pci_device.c. The code really doesn't care about the segment group as long as the pci_*_config functions access the right segment.