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

[Svyatoslav Ryhel]

вт, 26 трав. 2026 р. о 15:35 Bartosz Golaszewski <brgl@xxxxxxxxxx> пише:
>
> On Tue, May 26, 2026 at 2:29 PM Svyatoslav Ryhel <clamor95@xxxxxxxxx> wrote:
> >
> > вт, 26 трав. 2026 р. о 14:14 Bartosz Golaszewski <brgl@xxxxxxxxxx> пише:
> > >
> > > On Tue, 26 May 2026 12:03:59 +0200, Svyatoslav Ryhel <clamor95@xxxxxxxxx> said:
> > > > вт, 26 трав. 2026 р. о 12:51 Bartosz Golaszewski <brgl@xxxxxxxxxx> пише:
> > > >>
> > > >> On Sat, May 23, 2026 at 10:51 AM Svyatoslav Ryhel <clamor95@xxxxxxxxx> wrote:
> > > >> >
> > > >> > Document the Tegra modem pwseq used by various devices based on the Nvidia
> > > >> > Tegra SoC, describing its usage. The power sequence provides interaction
> > > >> > between the modem and SoC-specific interface configurations.
> > > >> >
> > > >> > Signed-off-by: Svyatoslav Ryhel <clamor95@xxxxxxxxx>
> > > >> > ---
> > > >>
> > > >> ...
> > > >>
> > > >> > +
> > > >> > +examples:
> > > >> > +  - |
> > > >> > +    #include <dt-bindings/gpio/gpio.h>
> > > >> > +
> > > >> > +    pwrseq-modem {
> > > >> > +        compatible = "nvidia,tegra-modem-pwrseq";
> > > >> > +
> > > >> > +        enable-gpios = <&gpio 165 GPIO_ACTIVE_HIGH>;
> > > >> > +        power-supply = <&vdd_3v3_vbat>;
> > > >> > +
> > > >> > +        nvidia,usb-bus = <&usb2>;
> > > >> > +    };
> > > >> > --
> > > >> > 2.51.0
> > > >> >
> > > >>
> > > >> I assume there's no such component as the tegra modem *pwrseq*?
> > > >
> > > > Hardware component, I assume no.
> > > >
> > > >> What is the relationship between this node and the "infineon,xmm6260"
> > > >> compatible node?
> > > >>
> > > >
> > > > The xmm6260 has a phandle reference to it. Since there is consumer
> > > > matching logic in the pwrseq driver I am leaning towards removing this
> > > > node entirely. This patches is still in non-final stage and I would
> > > > like to hear any opinions on the way to improving it.
> > > >
> > >
> > > 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.

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?

>
> Bart