Dear Julius,
Am 06.12.21 um 23:42 schrieb Julius Werner:
If I remember correctly, coreboot’s goal to only do minimal hardware
initialization originally meant, that the payload/OS does PCI
initialization.
FWIW, coreboot does do device initialization for things that are only
needed by the payload in other cases too: we've been doing display and
USB initialization that way for years. This only works in those cases
where you need to do a lot of very platform-specific stuff to turn
something on, but then after that it presents a very simple generic
API (like a framebuffer or standardized host controller interface),
but I think PCI also falls in that area. I think it's useful so that
payloads don't all need to implement that super SoC-specific stuff
individually.
It’s hard to draw a clear line. But let’s keep in mind, that the Linux
kernel has already working drivers.
In general, I don't think we should be too strict about what coreboot
should or shouldn't be in cases where someone just wants to add an
optional feature that doesn't introduce a huge maintenance burden on
the core framework. If someone doesn't like it they can just disable
the Kconfig and do PCI init in the payload / the kernel / via node.js
or whatever instead. This has clearly been useful on x86 platforms for
years, so I don't see why Arm platforms shouldn't be allowed to do it
as well.
I do not want to block or forbid anything. Your point about making it
configurable is very good. I think disabling PCI initialization is
currently not possible for x86 with `make menuconfig`. It’d be great if
it would be possible for ARM. The use case of having coreboot and the
payload with all drivers (Linux kernel) in the flash ROM chip, so a
build without PCI, graphics and USB init should be easily configurable.
But, currently, selecting Google Asurada in Kconfig (`make menuconfig`),
display initialization cannot be disabled, and I do not see a way to
disable USB init either.
Kind regards,
Paul
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