Re: [PATCH v6 1/2] usb: xhci-pci: add AMD Promontory 21 PCI glue

[Guenter Roeck]

On 5/17/26 14:21, Michal Pecio wrote:
> On Sun, 17 May 2026 22:04:06 +0900, Jihong Min wrote:
> > AMD Promontory 21 (PROM21) xHCI controllers use generic xHCI
> > operation, but the PCI function also exposes optional
> > controller-specific sensor functionality. Add a small PROM21 PCI glue
> > driver for AMD 1022:43fc and 1022:43fd controllers.
> >
> > The driver delegates USB host operation to the common xhci-pci core,
> > collects the parent-provided MMIO resource data, and creates a "hwmon"
> > auxiliary device for optional child drivers. Failure to create the
> > auxiliary device is logged but does not fail the xHCI probe, since the
> > auxiliary device is only needed for sensor support.
> >
> > Make the PROM21 PCI glue a hidden Kconfig tristate that follows
> > USB_XHCI_PCI. This keeps the glue built in with a built-in xhci-pci core
> > and builds it as a module with a modular xhci-pci core. A built-in
> > xhci-pci core must not hand PROM21 controllers to a PROM21 glue driver
> > that is only available as a module, otherwise USB behind those controllers
> > can be unavailable during initramfs and PROM21 temperature sensor support
> > may not appear until the controller is rebound after the module loads.
> >
> > Assisted-by: Codex:gpt-5.5
> > Signed-off-by: Jihong Min <hurryman2212@xxxxxxxxx>
> > Reviewed-by: Mario Limonciello (AMD) <superm1@xxxxxxxxxx>
> > Tested-by: Yaroslav Isakov <yaroslav.isakov@xxxxxxxxx>
> > ---
> >   drivers/usb/host/Kconfig                      |   7 +
> >   drivers/usb/host/Makefile                     |   1 +
> >   drivers/usb/host/xhci-pci-prom21.c            | 136 ++++++++++++++++++
> >   drivers/usb/host/xhci-pci.c                   |  11 ++
> >   drivers/usb/host/xhci-pci.h                   |   3 +
> >   include/linux/platform_data/usb-xhci-prom21.h |  22 +++
> >   6 files changed, 180 insertions(+)
> >   create mode 100644 drivers/usb/host/xhci-pci-prom21.c
> >   create mode 100644 include/linux/platform_data/usb-xhci-prom21.h
> >
> > diff --git a/drivers/usb/host/Kconfig b/drivers/usb/host/Kconfig
> > index 0a277a07cf70..89bf262235e1 100644
> > --- a/drivers/usb/host/Kconfig
> > +++ b/drivers/usb/host/Kconfig
> > @@ -42,6 +42,13 @@ config USB_XHCI_PCI
> >   	depends on USB_PCI
> >   	default y
> >   
> > +config USB_XHCI_PCI_PROM21
> > +	tristate
> > +	depends on X86
> > +	depends on USB_XHCI_PCI
> > +	default USB_XHCI_PCI
> > +	select AUXILIARY_BUS
> > +
>
> Instead of the X86 heuristic, would it be possible to build glue
> code if and only if SENSORS_PROM21_XHCI is enabled?
>
> This seems to work:
>
>   config SENSORS_PROM21_XHCI
>          tristate "AMD Promontory 21 xHCI temperature sensor"
> -       depends on USB_XHCI_PCI_PROM21
> +       depends on USB_XHCI_PCI
>
>   config USB_XHCI_PCI_PROM21
>          tristate
> -       depends on X86
>          depends on USB_XHCI_PCI
> -       default USB_XHCI_PCI
> +       default USB_XHCI_PCI if SENSORS_PROM21_XHCI != 'n'
>          select AUXILIARY_BUS
>
> I don't know if it's the best way, perhaps it would be preferable for
> the hwmon driver to select the glue, but then I'm not sure how to force
> glue to become 'y' when xhci-pci is 'y'.

Unless I am missing something, that would disable the entire controller
if the hwmon device is not enabled. That seems a bit draconian to me.

Guenter