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

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Message-ID: <20201014212259.ltckcgz2yrola7za@mobilestation>
Date:   Thu, 15 Oct 2020 00:22:59 +0300
From:   Serge Semin <Sergey.Semin@...kalelectronics.ru>
To:     Rob Herring <robh+dt@...nel.org>
CC:     Serge Semin <fancer.lancer@...il.com>,
        Felipe Balbi <balbi@...nel.org>,
        Mathias Nyman <mathias.nyman@...el.com>,
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Subject: Re: [PATCH 20/20] arch: dts: Fix DWC USB3 DT nodes name

On Wed, Oct 14, 2020 at 01:35:16PM -0500, Rob Herring wrote:
> 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.

Ok. I'll change them in v3.

-Sergey

> 
> Rob