Re: [PATCH v2 1/2] dt-bindings: soc: tegra: Document Nvidia Tegra modem pwrseq

[Bartosz Golaszewski]

On Tue, May 26, 2026 at 2:55 PM Svyatoslav Ryhel <clamor95@xxxxxxxxx> wrote:
>
> > > >
> > > > The node attached to the pwrseq provider device should represent a real
> > > > hardware component. Are the enable-gpios and power-supply lines connected
> > > > to the modem package?
> > >
> > > Yes, enable-gpio is connected to the modem and signals that USB is set
> > > and ready to work with the modem, while power-supply is an optional
> > > supply connected to the modem's vbus input.
> > >
> >
> > The modem is a hard-wired USB device? Do you implement it as a
> > platform driver or a USB driver?
> >
>
> It is not a traditional USB device. XMM6260 is an embedded modem used
> in the Tegra phones, it is linked with the AP using USB line in HSIC
> mode. The driver is implemented as a platform device since it does not
> interacts with the exposed USB device directly, it just ensures that
> USB device is properly configured and is ready for IPC.
>
> > Is there a connector of any kind that could be used as the HW
> > component represented by the pwrseq device?
>
> I assume control over USB line is the HW base, but as I have said, I
> can integrate binding in the modem node itself, and pwrseq can get all
> it needs from the match. Pwrseq framework states "This framework is
> designed to abstract complex power-up sequences that are shared
> between multiple logical devices in the Linux kernel." it does not say
> that it must represent some specific hardware.
>

No, not at all. We just can't make up any imaginary, logical "pwrseq"
devices and describe them in DT bindings.

> Using pwrseq allows modem driver to be SoC independent since USB line
> handling is moved into SoC specific power sequence, and this modem is
> used in Exynos and OMAP too with similar setup but they all have
> different USB controllers. Maybe you can point me where SoC specific
> USB controller handling can be implemented?
>

I'm not sure I'm following. Can you rephrase or point me where OMAP
and Samsung implement it?

Bart