From: Heikki Krogerus <heikki.krogerus@linux.intel.com>
To: Hans de Goede <hdegoede@redhat.com>
Cc: John Stultz <john.stultz@linaro.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
lkml <linux-kernel@vger.kernel.org>,
Yu Chen <chenyu56@huawei.com>, Rob Herring <robh+dt@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Chunfeng Yun <chunfeng.yun@mediatek.com>,
Felipe Balbi <balbi@kernel.org>,
Andy Shevchenko <andy.shevchenko@gmail.com>,
Jun Li <lijun.kernel@gmail.com>,
Valentin Schneider <valentin.schneider@arm.com>,
Linux USB List <linux-usb@vger.kernel.org>,
"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS"
<devicetree@vger.kernel.org>
Subject: Re: [RFC][PATCH 2/3] usb: roles: Add usb role switch notifier.
Date: Fri, 4 Oct 2019 11:00:58 +0300 [thread overview]
Message-ID: <20191004080058.GD1048@kuha.fi.intel.com> (raw)
In-Reply-To: <9cfccb6a-fba1-61a3-3eb6-3009c2f5e747@redhat.com>
On Thu, Oct 03, 2019 at 10:56:24PM +0200, Hans de Goede wrote:
> Hi,
>
> On 03-10-2019 22:45, John Stultz wrote:
> > On Thu, Oct 3, 2019 at 4:26 AM Greg Kroah-Hartman
> > <gregkh@linuxfoundation.org> wrote:
> > >
> > > On Wed, Oct 02, 2019 at 11:16:16PM +0000, John Stultz wrote:
> > > > From: Yu Chen <chenyu56@huawei.com>
> > > >
> > > > This patch adds notifier for drivers want to be informed of the usb role
> > > > switch.
> > >
> > > Ick, I hate notifiers, they always come back to cause problems.
> > >
> > > What's just wrong with a "real" call to who ever needs to know this?
> > > And who does need to know this anyway? Like Hans said, if we don't have
> > > a user for it, we should not add it.
> >
> > So in this case, its used for interactions between the dwc3 driver and
> > the hikey960 integrated USB hub, which is controlled via gpio (which I
> > didn't submit here as I was trying to keep things short and
> > reviewable, but likely misjudged).
> >
> > The HiKey960 has only one USB controller, but in order to support both
> > USB-C gadget/OTG and USB-A (host only) ports. When the USB-C
> > connection is attached, it powers down and disconnects the hub. When
> > the USB-C connection is detached, it powers the hub on and connects
> > the controller to the hub.
>
> When you say one controller, do you mean 1 host and 1 gadget controller,
> or is this one of these lovely devices where a gadget controller gets
> abused as / confused with a proper host controller?
>
> And since you are doing a usb-role-switch driver, I guess that the
> role-switch is integrated inside the SoC, so you only get one pair
> of USB datalines to the outside ?
Unless I'm mistaken, the dwc3 driver in this case is the
usb-role-switch. The DWC3 IP includes both USB dost and device blocks,
i.e. it's a dual role controller. Drivers like tcpm.c that negotiate
the actual role need to tell the outcome of the negotiation to the
dwc3 driver. So I think this part is OK.
The platform has also some kind of discrete switch for routing the
signals to either Standard-A (the hub) or Type-C connector, so it does
not represent the usb-role-switch. It should however affect the USB role,
as if that switch routes the data signals to the Standard-A port (to
the hub) instead of USB Type-C, the USB role needs to be fixed to host
mode.
I guess this series does not include the driver for that discrete
switch/mux. I don't remember/know how that switch was planned to be
handled.
> This does seem rather special, it might help if you can provide a diagram
> with both the relevant bits inside the SoC as well as what lives outside
> the Soc. even if it is in ASCII art...
thanks,
--
heikki
next prev parent reply other threads:[~2019-10-04 8:01 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-02 23:16 [RFC][PATCH 0/3] dwc3 role-switch handling for HiKey960 John Stultz
2019-10-02 23:16 ` [RFC][PATCH 1/3] dt-bindings: usb: generic: Add role-switch-default-host binding John Stultz
2019-10-02 23:16 ` [RFC][PATCH 2/3] usb: roles: Add usb role switch notifier John Stultz
2019-10-03 9:25 ` Hans de Goede
2019-10-03 20:37 ` John Stultz
2019-10-03 20:51 ` Hans de Goede
2019-10-04 8:12 ` Heikki Krogerus
2019-10-15 5:39 ` John Stultz
2019-10-16 7:27 ` Hans de Goede
2019-10-18 5:55 ` John Stultz
2019-10-18 8:06 ` Hans de Goede
2019-10-18 18:39 ` John Stultz
2019-10-18 19:30 ` Hans de Goede
2019-10-18 19:53 ` John Stultz
2019-10-18 19:59 ` Hans de Goede
2019-10-18 20:12 ` John Stultz
2019-10-18 20:21 ` Hans de Goede
2019-10-18 20:37 ` John Stultz
2019-10-18 21:05 ` Hans de Goede
2019-10-22 5:58 ` John Stultz
2019-11-14 10:11 ` Hans de Goede
2019-11-15 0:23 ` John Stultz
2019-10-16 9:10 ` Hans de Goede
2019-10-03 11:26 ` Greg Kroah-Hartman
2019-10-03 20:45 ` John Stultz
2019-10-03 20:56 ` Hans de Goede
2019-10-03 21:33 ` John Stultz
2019-10-06 15:22 ` Hans de Goede
2019-10-15 7:03 ` John Stultz
2019-10-04 8:00 ` Heikki Krogerus [this message]
2019-10-02 23:16 ` [RFC][PATCH 3/3] usb: dwc3: Registering a role switch in the DRD code John Stultz
2019-10-15 8:25 ` Roger Quadros
2019-10-15 19:10 ` John Stultz
2019-10-16 9:24 ` Roger Quadros
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