Re: [PATCH v2] platform/x86: p2sb: Defer P2SB device scan when P2SB device has func 0

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On Mar 04, 2024 / 12:04, Hans de Goede wrote:
> So the p2sb_bar(devfn=0) call actually only happens on Goldmont from:
> 3) mfd/lpc_ich for pinctrl    devfn = 0
> and then only when the ACPI tables fail to properly describe the GPIO
> controllers as ACPI devices, if the GPIO controllers are described
> in ACPI, which they are on the ASUS VivoBook D540NV-GQ065T then that
> call gets skipped.
> So on the ASUS VivoBook D540NV-GQ065T p2sb_bar(devfn=0) gets never
> called. Which explains why not caching it fixes things. I assume that this
> laptop just seems not likes the P2SB is touched at all and by not caching
> the BAR for the P2SB it ends up not getting touched at all.

Thanks for sharing the insights.

> This also means that likely the P2SB devfn itself generally speaking is
> often not touched on Goldmont platforms. So we can avoid the lockdep
> issue on PCI bus rescan there by caching the SPI controller
> PCI_DEVFN(13, 2) devfn from fs_initcall(), since that will be the only
> devfn for which p2sb_bar() will get called (except on hw with the
> GPIO controller missing from the ACPI tables which should be rare).

Oh, this sounds a great idea.

> I have prepared a follow up patch to your v3 to cache the
> SPI controller devfn instead of the P2SB devfn at fs_initcall()
> time. I'll post this shortly and I'll also ask the bug reporter
> to test the combination of our 2 patches.

Thanks a lot. Looking forward to the results.

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