From: Peter Chen <hzpeterchen@gmail.com>
To: Lu Baolu <baolu.lu@linux.intel.com>
Cc: felipe.balbi@linux.intel.com,
Mathias Nyman <mathias.nyman@intel.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Lee Jones <lee.jones@linaro.org>,
Heikki Krogerus <heikki.krogerus@linux.intel.com>,
Liam Girdwood <lgirdwood@gmail.com>,
Mark Brown <broonie@kernel.org>,
linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org,
Roger Quadros <rogerq@ti.com>
Subject: Re: [PATCH v10 2/7] usb: mux: add generic code for dual role port mux
Date: Sat, 4 Jun 2016 10:28:38 +0800 [thread overview]
Message-ID: <20160604022838.GA26936@shlinux2> (raw)
In-Reply-To: <5751AAEE.2090001@linux.intel.com>
On Sat, Jun 04, 2016 at 12:06:06AM +0800, Lu Baolu wrote:
> Hi Peter,
>
> On 06/03/2016 03:41 PM, Peter Chen wrote:
> > On Thu, Jun 02, 2016 at 09:37:24AM +0800, Lu Baolu wrote:
> >> > Several Intel platforms implement USB dual role by having completely
> >> > separate xHCI and dwc3 IPs in PCH or SOC silicons. These two IPs share
> >> > a single USB port. There is another external port mux which controls
> >> > where the data lines should go. While the USB controllers are part of
> >> > the silicon, the port mux design are platform specific.
> >> >
> >> > This patch adds the generic code to handle such multiple roles of a
> >> > usb port. It exports the necessary interfaces for other components to
> >> > register or unregister a usb mux device, and to control its role.
> >> > It registers the mux device with sysfs as well, so that users are able
> >> > to control the port role from user space.
> >> >
> >> > Some other archs (e.g. Renesas R-Car gen2 SoCs) need an external mux to
> >> > swap usb roles as well. This code could also be leveraged for those archs.
> >> >
> > Sorry to review this so late,
>
> It doesn't matter. Thanks for review. Comments are always welcome.:-)
>
> > from my point,it is a dual-role switch
> > driver too,
>
> No, it's not a dual-role switch driver, but a driver for USB port multiplexing.
>
> One example of port multiplexing can be found in several Intel SOC and PCH
> chips, inside of which, there are two independent USB controllers: host and
> device. They might share a single port and this port could be configured to
> route the line to one of these two controllers. This patch introduced a generic
> framework for port mux drivers. It aids the drivers to handle port mux by
> providing interfaces to 1) register/unregister a mux device; 2) lookup the
> mux device; and 3) switch the port.
>
For this case, I can't see it is different with dual-role switch. Your
case is just like Renesas case, which uses two different drivers between
peripheral and host[1].
> Port multiplexing isn't equal to USB dual role. There are other cases in today's
> systems. In several Intel PCH chips, there equips two USB host controllers: ehci
> and xhci. The xhci USB2 ports are multiplexed with ehci. This guarantees all
> USB ports work even running an old version of OS which lacks of USB3 support.
> In theory, we can create a driver for the port mux and switch the ports between
> xhci and ehci, but that's silly, isn't it? Why not always USB3?:-)
>
> Another case is xHCI debug capability. The xHCI host controller might equip
> a unit for system debugging (refer to 7.6 of xHCI spec). The debugging unit is
> independent of xhci host controller. But it shares its port with xhci. Software
> could switch the port between xhci and the debugging unit through the registers
> defined in xHCI spec.
>
Yes, above two are different with dual role switch. But in your code and
Kconfig, it seems this framework is dedicated for dual-role. Eg:
+menuconfig USB_PORTMUX
+ bool "USB dual role port MUX support"
+ help
+ Generic USB dual role port mux support.
I think a general dual role port mux is necessary, it can be used to
manage different dual-role switch method, eg
- ID pin
- External connector through GPIO
- SoC register
- sysfs
- type-C events
But this code is better co-work with OTG/Dual-role framework, we'd
better have only interface that the user can know which role for the
current port.
[1] https://lkml.org/lkml/2016/4/7/115
--
Best Regards,
Peter Chen
next prev parent reply other threads:[~2016-06-04 2:34 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-02 1:37 [PATCH v10 0/7] usb: add support for Intel dual role port mux Lu Baolu
2016-06-02 1:37 ` [PATCH v10 1/7] regulator: fixed: add support for ACPI interface Lu Baolu
2016-06-08 4:42 ` Greg Kroah-Hartman
2016-06-08 13:43 ` Mark Brown
2016-06-08 15:46 ` Greg Kroah-Hartman
2016-06-09 2:43 ` Lu Baolu
2016-06-02 1:37 ` [PATCH v10 2/7] usb: mux: add generic code for dual role port mux Lu Baolu
2016-06-03 7:41 ` Peter Chen
2016-06-03 8:16 ` Heikki Krogerus
2016-06-03 9:20 ` Peter Chen
2016-06-03 16:06 ` Lu Baolu
2016-06-04 2:28 ` Peter Chen [this message]
2016-06-05 6:55 ` Lu Baolu
2016-06-05 8:33 ` Jun Li
2016-06-05 8:46 ` Lu Baolu
2016-06-06 1:08 ` Jun Li
2016-06-06 2:30 ` Lu Baolu
2016-06-06 2:05 ` Peter Chen
2016-06-06 2:45 ` Lu Baolu
2016-06-06 6:48 ` Peter Chen
2016-06-06 1:25 ` Peter Chen
2016-06-06 3:04 ` Lu Baolu
2016-06-06 7:02 ` Roger Quadros
2016-06-07 3:03 ` Jun Li
2016-06-07 6:27 ` Lu Baolu
2016-06-07 6:34 ` Jun Li
2016-06-07 9:27 ` Lu Baolu
2016-06-07 12:49 ` Roger Quadros
2016-06-07 9:53 ` Lu Baolu
2016-06-07 12:58 ` Roger Quadros
2016-06-07 13:04 ` Felipe Balbi
2016-06-07 14:02 ` Roger Quadros
2016-06-07 15:05 ` Felipe Balbi
2016-06-08 3:04 ` Jun Li
[not found] ` <5757A8CB.90402@linux.intel.com>
2016-06-08 6:20 ` Jun Li
2016-06-08 6:25 ` Peter Chen
2016-06-08 7:58 ` Roger Quadros
2016-06-06 7:02 ` Peter Chen
2016-06-06 7:35 ` Lu Baolu
2016-06-02 1:37 ` [PATCH v10 3/7] usb: mux: add driver for Intel gpio controlled " Lu Baolu
2016-06-02 1:37 ` [PATCH v10 4/7] usb: mux: add driver for Intel drcfg " Lu Baolu
2016-06-02 1:37 ` [PATCH v10 5/7] mfd: intel_vuport: Add Intel virtual USB port MFD Driver Lu Baolu
2016-06-02 1:37 ` [PATCH v10 6/7] usb: pci-quirks: add Intel USB drcfg mux device Lu Baolu
2016-06-08 4:45 ` Greg Kroah-Hartman
2016-06-08 7:56 ` Lu Baolu
2016-06-08 15:45 ` Greg Kroah-Hartman
2016-06-09 2:39 ` Lu Baolu
2016-06-16 0:27 ` Lu Baolu
2016-06-18 0:58 ` Greg Kroah-Hartman
2016-06-19 9:52 ` Lu Baolu
2016-06-02 1:37 ` [PATCH v10 7/7] MAINTAINERS: add maintainer entry for Intel USB dual role mux drivers Lu Baolu
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