Re: port-arm/57643: aarch64: smmu(4) seems mandatory for some SoC and/or memory configuration

[Rin Okuyama <rokuyama.rk%gmail.com@localhost>]

Some unsuccessful tries:

(1) UEFI firmware crashes for another 2GB module by other vendor.

(2) wm(4) driver (since rev 1.69 back to 2004) imposes a boundary
    condition for TX/RX descriptors, to forbid across 4GB boundaries:

http://cvsweb.netbsd.org/bsdweb.cgi/src/sys/dev/pci/if_wm.c#rev1.69
https://nxr.netbsd.org/xref/src/sys/dev/pci/if_wm.c#wm_alloc_tx_descs

    But this is irrelevant in this case; descriptor buffer is not
    across 4GB boundaries when this symptom is observed.

(3) The problem cannot be reproduced for a I226 card:

igc0 at pci3 dev 0 function 0: Intel(R) Ethernet Controller I226-V (rev. 0x04)

    But this is a dual port card, and it may be just because a
    device is internally connected via ppb(4):

pci1 at acpipchb1 bus 1
pci1: i/o space, memory space enabled, rd/line, rd/mult, wr/inv o
ppb0 at pci1 dev 0 function 0: vendor 1b21 product 1182 (rev. 0x00)
ppb0: PCI Express capability version 2 <Upstream Port of PCI-E Switch>
pci2 at ppb0 bus 2
pci2: i/o space, memory space enabled
ppb1 at pci2 dev 3 function 0: vendor 1b21 product 1182 (rev. 0x00)
ppb1: PCI Express capability version 2 <Downstream Port of PCI-E
Switch> x1 @ 5.0GT/s
pci3 at ppb1 bus 3

    I ordered a single port I226 card as well as a dual port I225 in
    order to confirm this scenario.

Thanks,
rin