Re: [PATCH 2/2] PCI: quirks: Drop unassignable 32 GiB BAR 4 on Tenstorrent Blackhole

[sashiko-bot@kernel.org]

> Tenstorrent Blackhole cards expose a 32 GiB BAR 4 that is unused by most
> software talking to the card. This BAR cannot be assigned on hosts whose
> PCI aperture is smaller than 32 GiB (e.g some ARM/RISC-V systems). This
> failure also results in BAR 0 (256 MiB) and 2 (2 MiB) being unassigned
> because bridge windows are sized as the sum of all enabled child BARs.
> This makes the card completely unusable on such systems.
> 
>     spacemit-k1-pcie 80000000.pcie: PCI host bridge to bus 0000:00
>     pci_bus 0000:00: root bus resource [bus 00-ff]
>     pci_bus 0000:00: root bus resource [io  0x100000-0x1fffff] (bus address [0x10000-0x10ffff])
>     pci_bus 0000:00: root bus resource [mem 0x1100110000-0x117fffffff] (bus address [0x00110000-0x7fffffff])
>     pci_bus 0000:00: root bus resource [mem 0x1800000000-0x18ffffffff pref]
> 
>     <snip>
> 
> [ ... ]
> bridge window then sizes to BARs 0/2 and succeeds. This was tested on a
> Spacemit-K3 RISC-V board that has only 4GiB of BAR space. tt-smi and
> tt-bh-linux are able to run on the card.
> 
> Signed-off-by: Anirudh Srinivasan <asrinivasan@oss.tenstorrent.com>

Sashiko has reviewed this patch and found no issues. It looks great!

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Sashiko AI review · https://sashiko.dev/#/patchset/20260824-blackhole_quirk-v1-0-fc004672cdbd@oss.tenstorrent.com?part=2