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

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Message-ID: <20201014143720.yny3jco5pkb7dr4b@mobilestation>
Date:   Wed, 14 Oct 2020 17:37:20 +0300
From:   Serge Semin <Sergey.Semin@...kalelectronics.ru>
To:     Felipe Balbi <balbi@...nel.org>
CC:     Serge Semin <fancer.lancer@...il.com>,
        Mathias Nyman <mathias.nyman@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rob Herring <robh+dt@...nel.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>,
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Subject: Re: [PATCH 20/20] arch: dts: Fix DWC USB3 DT nodes name

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.

-Sergey

> 
> In any case, I don't have any problems with this, so I'll let other
> folks comment.
> 
> -- 
> balbi