linux-kernel - Re: [PATCH 20/20] arch: dts: Fix DWC USB3 DT nodes name

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Date:   Wed, 14 Oct 2020 13:35:16 -0500
From:   Rob Herring <robh+dt@...nel.org>
To:     Serge Semin <Sergey.Semin@...kalelectronics.ru>
Cc:     Felipe Balbi <balbi@...nel.org>,
        Serge Semin <fancer.lancer@...il.com>,
        Mathias Nyman <mathias.nyman@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jason Cooper <jason@...edaemon.net>,
        Andrew Lunn <andrew@...n.ch>,
        Gregory Clement <gregory.clement@...tlin.com>,
        Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
        Kukjin Kim <kgene@...nel.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Santosh Shilimkar <ssantosh@...nel.org>,
        Shawn Guo <shawnguo@...nel.org>, Li Yang <leoyang.li@....com>,
        Benoît Cousson <bcousson@...libre.com>,
        Tony Lindgren <tony@...mide.com>,
        Patrice Chotard <patrice.chotard@...com>,
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        linux-arm-msm <linux-arm-msm@...r.kernel.org>
Subject: Re: [PATCH 20/20] arch: dts: Fix DWC USB3 DT nodes name

On Wed, Oct 14, 2020 at 9:37 AM Serge Semin
<Sergey.Semin@...kalelectronics.ru> wrote:
>
> On Wed, Oct 14, 2020 at 05:09:37PM +0300, Felipe Balbi wrote:
> >
> > Hi Serge,
> >
> > Serge Semin <Sergey.Semin@...kalelectronics.ru> writes:
> > > In accordance with the DWC USB3 bindings the corresponding node name is
> > > suppose to comply with Generic USB HCD DT schema, which requires the USB
> >
>
> > DWC3 is not a simple HDC, though.
>
> Yeah, strictly speaking it is equipped with a lot of vendor-specific stuff,
> which are tuned by the DWC USB3 driver in the kernel. But after that the
> controller is registered as xhci-hcd device so it's serviced by the xHCI driver,
> which then registers the HCD device so the corresponding DT node is supposed
> to be compatible with the next bindings: usb/usb-hcd.yaml, usb/usb-xhci.yaml
> and usb/snps,dwc3,yaml. I've created the later one so to validate the denoted
> compatibility.
>
> >
> > > nodes to have the name acceptable by the regexp: "^usb(@.*)?" . But a lot
> > > of the DWC USB3-compatible nodes defined in the ARM/ARM64 DTS files have
> > > name as "^dwc3@.*" or "^usb[1-3]@.*" or even "^dwusb@.*", which will cause
> > > the dtbs_check procedure failure. Let's fix the nodes naming to be
> > > compatible with the DWC USB3 DT schema to make dtbs_check happy.
> > >
> > > Note we don't change the DWC USB3-compatible nodes names of
> > > arch/arm64/boot/dts/apm/{apm-storm.dtsi,apm-shadowcat.dtsi} since the
> > > in-source comment says that the nodes name need to be preserved as
> > > "^dwusb@.*" for some backward compatibility.
> >
>
> > interesting, compatibility with what? Some debugfs files, perhaps? :-)
>
> Don't really know.) In my experience the worst type of such compatibility is
> connected with some bootloader magic, which may add/remove/modify properties
> to nodes with pre-defined names.

I seriously doubt anyone is using the APM machines with DT (even ACPI
is somewhat doubtful). I say change them. Or remove the dts files and
see what happens. Either way it can always be reverted.

Rob