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

[Svyatoslav Ryhel]

вт, 26 трав. 2026 р. о 16:14 Bartosz Golaszewski <brgl@xxxxxxxxxx> пише:
>
> 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.
>

Ye, ye, sure, pwrseq framework is quite flexible and I am not stating
this bindings is mandatory.

> > 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?
>

They did not.

The XMM6260 modem is used not only in the Tegra phones but in the OMAP
and Exynos based too. Replicant tried to implement support locally
with midas devices and they had some progress. From what I have seen
generic implementation I am proposing will work with any of those 3
SoCs maybe with some slight tweaks, only part that is totally
different and SoC specific is how USB controller used by the modem is
handled (well and IPC but that is out of scope of this patchset
anyway).

Obviously, non of the 3 vendors have submitted any mainline patches,
everything is in the downstream forks. I have investigated a bit how
this modem works on my Tegra phone and re-implemented it to work with
mainline kernel (I don't have Exynos and OMAP devices to play with). I
have come up with generic platform driver which handles modem
configuration and a SoC specific part which performs USB controller
bind/probe when modem is ready to handle the USB. ATM this SoC
specific part is available and tested only for Tegra devices.

> Bart