Hello, Alex,
Sorry, it's me, again ;-)
Can I control the assignment of PCIe lanes at the linux level?
After understanding the PCIe tree, I'm back where I started.
I now _understand_ what happened, but still want to be able to _change_ that.
Compare my previous / after settings:
before after
Slot 1 Tesla Tesla
lanes x16 x16
Slot 2 quad NIC quad NIC
lanes x4 x4
Slot 3 Quadro2000 quad NIC
lanes x16 x4
Slot 4 quad NIC Quadro2000
x1 x8
x1-slot: empty empty
To summarize asssignement of PCIe lanes:
before: 16 4 16 1 0 total = 37
after: 16 4 4 8 0 total = 32
So, in the "before" setup, there was neither a lack of slot 4 capability to
deliver x4 (it can deliver x8 afterwards).
Nor there was a lack of total pcie lanes, if I only had been able to contain
the greed of the Quadro video card in Slot 3.
I googled across somebody saying that the kernel tries to follow bios
recommendations, but not blindly (sorry, can' find that again). From that I
conclude that those assignments are not written in stone after bootup, are
they?
When I read the man pages of pcilib & setpci, I seet that in principle I could
poke into the registers of pci devices.
And there are lots of interesting things below /sys/devices/pci0000:00
attracting my naive curiousity.
So I see the reengineering way of reinventing the wheel, work through all the
data sheets and after some months of hard work and some bricked pieces of
hardware, I may end up with a solution.
But I woulnd't mind if somebody had done this already ;-)
Is there a document, a tool, a config file, a /proc/bus/where/ever or such
where I can control the assignment of PCIe lanes to the slots at some higher
level?
Wolfgang Rosner
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