linux-kernel - Re: [PATCH v2 3/4] MIPS: BCM63xx: enable EHCI for DWV-S0 board

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Date:   Tue, 11 Aug 2020 11:09:20 +0200
From:   Philippe Mathieu-Daudé <f4bug@...at.org>
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     Álvaro Fernández Rojas <noltari@...il.com>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Jonas Gorski <jonas.gorski@...il.com>,
        bcm-kernel-feedback-list <bcm-kernel-feedback-list@...adcom.com>,
        "open list:BROADCOM NVRAM DRIVER" <linux-mips@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 3/4] MIPS: BCM63xx: enable EHCI for DWV-S0 board

Hi Florian,

On Tue, Aug 11, 2020 at 4:33 AM Florian Fainelli <f.fainelli@...il.com> wrote:
> On 8/9/2020 11:49 AM, Philippe Mathieu-Daudé wrote:
> > Hi Álvaro,
> >
> > On Fri, Aug 7, 2020 at 12:05 PM Álvaro Fernández Rojas
> > <noltari@...il.com> wrote:
> >>
> >> EHCI and OHCI share the same USB ports. Therefore, if the board has OHCI
> >> it should also have EHCI.
> >
> > This statement isn't correct. OHCI doesn't imply EHCI...
> > (although the opposite is almost always true).
> >
> > Now per 6358-PB01-R the bcm6358 indeed has a EHCI controller.
> >
> > Do you mind rewording the commit description?
>
> Is not it that a single USB port is used and we need the EHCI controller
> active in order for the correct speed negotiation to occur?

Yes. What sounds odd is "if the board has OHCI it should also have EHCI."

This is true for this particular board because its chipset is a bcm6358,
but I'm worried it might later confuse other developers. For example the
bcm6348 has a OHCI controller, but that doesn't imply its port can be
used as EHCI.

Regards,

Phil.

> --
> Florian