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@xxxxxxxxxxxxxxxxxxx> wrote: > > > > > > On Wed, Oct 02, 2019 at 11:16:16PM +0000, John Stultz wrote: > > > > From: Yu Chen <chenyu56@xxxxxxxxxx> > > > > > > > > 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
