Re: [PATCH] dt-bindings: usb: ehci: Increase the number of PHYs

From: Geert Uytterhoeven <geert@linux-m68k.org>
To: Rob Herring <robh+dt@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
	Biju Das <biju.das.jz@bp.renesas.com>,
	Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>,
	Linux USB List <linux-usb@vger.kernel.org>,
	"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
	<devicetree@vger.kernel.org>,
	"open list:MEDIA DRIVERS FOR RENESAS - FCP" 
	<linux-renesas-soc@vger.kernel.org>
Subject: Re: [PATCH] dt-bindings: usb: ehci: Increase the number of PHYs
Date: Thu, 16 Jun 2022 09:52:53 +0200	[thread overview]
Message-ID: <CAMuHMdU3PnY6yZf70kB9wme7_WTjcPJwmzo--Ua3vJ45w7mD8w@mail.gmail.com> (raw)
In-Reply-To: <CAL_JsqJbmdJd6+D9zog6NwF_LPO5QC_HsODg4FHLJOnMmPP-mg@mail.gmail.com>

Hi Rob,

On Wed, Jun 15, 2022 at 7:24 PM Rob Herring <robh+dt@kernel.org> wrote:
> On Wed, Jun 15, 2022 at 7:53 AM Geert Uytterhoeven
> <geert+renesas@glider.be> wrote:
> >
> > "make dtbs_check":
> >
> >     arch/arm/boot/dts/r8a77470-iwg23s-sbc.dtb: usb@ee080100: phys: [[17, 0], [31]] is too long
> >             From schema: Documentation/devicetree/bindings/usb/generic-ehci.yaml
> >     arch/arm/boot/dts/r8a77470-iwg23s-sbc.dtb: usb@ee0c0100: phys: [[17, 1], [33], [21, 0]] is too long
> >             From schema: Documentation/devicetree/bindings/usb/generic-ehci.yaml
> >
> > Some USB EHCI controllers (e.g. on the Renesas RZ/G1C SoC) have multiple
> > PHYs.  Increase the maximum number of PHYs to 3, which is sufficient for
> > now.
>
> Maybe not so 'generic'. Why are there 3? I understand USB3 HCI having
> 2 for SS and HS. Is it for multiple ports? There's a thread about that
> currently (Mediatek IIRC) and how to handle multiple phys.

TBH, I don't know for sure. I've never been much into USB, and the
RZ/G1C USB architecture differs from other Renesas SoCs in the
same family.

This is USB2, not USB3.  There are two channels of OHCI/EHCI, and
two channels of USB OTG, all with corresponding PHYs (4 in total).
The first OHCI/EHCI combo is linked to one of the host PHYs, and one
of the OTG PHYs, so that makes 2 PHYs.
The second OHCI/EHCI combo is linked to the other host PHY, and to
both OTG PHYs, so that makes 3 PHYs. IIRC the third link was due to
some dependency between the 2 OTG PHYs.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds