NetBSD Problem Report #56846

From  Wed May 18 22:53:15 2022
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Date: Wed, 18 May 2022 22:53:12 +0000 (UTC)
Subject: Hardware lockup on laptops with ToPIC95B Cardbus controller
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>Number:         56846
>Category:       port-i386
>Synopsis:       Hardware lockup on laptops with ToPIC95B Cardbus controller
>Confidential:   no
>Severity:       serious
>Priority:       low
>Responsible:    port-i386-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed May 18 22:55:00 +0000 2022
>Originator:     Jaroslaw Kurkiewicz
>Release:        9.2
NetBSD 9.2 NetBSD 9.2 (GENERIC) i386
Write buffering (or more accurately PCI Posted Writes I believe) should not be enabled by default on ToPIC95B Cardbus controllers. As a result, system completely locks up under any kind of heavy Cardbus activity. Observed on Toshiba Satellite Pro 440CDT with 3COM Cardbus 3c575CT Ethernet card.

It might also affect ToPIC95.

Put heavy load on Cardbus on any old Toshiba laptop with 6.B0 Toshiba BIOS and ToPIC95B controller. Any attempt to, for example, saturate a 100Mbit/s Ethernet link results in irrecoverable hardware lockup.
Fix: Quick fix is to disable PCI Posted Writes. Since datasheet seems to be unobtainable further tests could prove whether it can be reenabled at some stage. I believe the following change in line 765 of pccbb_chipinit() might be enough but I don't know the codebase at all: 

if (sc->sc_chipset != CB_TOPIC95B)

Related Linux kernel bug 55961 should provide sufficient information and inspiration.

Workaround 1: Switch controller to PCIC-compatible mode and avoid using Cardbus cards.

Workaround 2: Do not put heavy load on Cardbus. (Following network card example the problem mostly disappears if the card is switched to 10MBit/s, half-duplex mode).

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