[RFCv2 usb-next 0/3] initialize (multiple) PHYs in xhci-plat

Mon Jul 17 00:21:07 PDT 2017

Hi,
On Sat, 2017-07-15 at 14:11 +0200, Martin Blumenstingl wrote:
> Hi,
> 
> On Sat, Jul 15, 2017 at 11:33 AM, Chunfeng Yun
> <chunfeng.yun at mediatek.com> wrote:
> > Hi Martin,
> >
> > On Thu, 2017-07-13 at 12:59 +0200, Martin Blumenstingl wrote:
> >> This series is the outcome of a discussion with Felipe Balbi,
> >> see [0] and [1].
> >> The quick-summary of this is:
> >> - dwc3 already takes one USB2 and one USB3 PHY and initializes these
> >>   correct
> >> - some other HCI platform drivers (like ehci-platform.c, xhci-mtk.c and
> >>   ohci-platform.c) do not have a limitation on the number of PHYs - they
> >>   support one PHY per actual host port
> >> - Amlogic Meson GXL and GXM SoCs come with a dwc3 IP block which has two
> >>   or three USB2 ports enabled on the internal root-hub. The SoCs also
> >>   provide separate USB2 PHYs, one per port. All USB2 PHYs (which are
> >>   internally "connected" to the dwc3 roothub) need to be powered on,
> >>   otherwise USB devices cannot be enumerated (even if just one PHY is
> >>   disabled and if the device is plugged into another, enabled port)
> >>
> >> In my first attempt to get USB supported on the GXL and GXM SoCs I tried
> >> to work-around the problem that I could not pass multiple PHYs to the
> >> dwc3 controller.
> >> This was rejected by Rob Herring (which was definitely the thing to do in
> >> my opinion), see [2]
> >>
> >> This series adds a new "platform-roothub". This can be configured through
> >> devicetree by passing a child-node with "reg = <0>" to the USB
> >> controller. Additionally there has to be a child-node for each port on
> >> the root-hub. Each of the child-nodes takes a "phys" and "phy-names"
> >> property. This allows modeling the root-hub in devicetree similar to the
> >> USB device binding (documented in devicetree/bindings/usb/usb-device.txt)
> >> This avoids and backwards-compatibility problems (which was a concern
> >> regardless of the solution, see [3]) since the binding for the root-hub
> >> was previously not specified (and we're not using the "phys" property of
> >> the controller, which might have served different purposes before,
> >> depending on the drivers).
> >>
> >> Additionally this integrates the new platform-roothub into xhci-plat.c
> >> which automatically enables it for the dwc3 driver (in host-mode).
> >>
> > How to handle the phy0(one u2phy and one u3phy) when port1 support
> > dual-role mode? leave them to peripheral side as felipe suggested
> > before? If so, no port1 node for roothub, is there any problem when
> > change the port1 to host-only mode?
> on Amlogic Meson GXL we have the following IP blocks:
> - 2x USB2 PHYs, some external component has to tell them which mode
> (host/device) they should operate in
> - there is an additional (1x) USB3 PHY with built-in OTG detection logic
> 
> on Amlogic Meson GXL it could work like this:
> USB2 and USB3 phy0 can be passed to the root-hub. Additionally the
> USB2 phy0 could be passed to the USB3 PHY. The USB3 PHY would then
> tell the USB2 PHY in which mode it should operate.
> 
> please note that device mode and OTG support on Amlogic Meson GXL is
> more complicated, as it uses dwc2 and dwc3 controllers in combination:
> - dwc3 is reponsible for host-only mode
> - dwc2 is responsible for device-only mode
> - OTG detection is done by the USB3 PHY
> 
> would you mind sharing a short overview of host/device/OTG support
> works on Mediatek SoCs? I assume that the Amlogic Meson GXL
> implementation is quite special, so comparing this with another
> implementation (for example the Mediatek one) may help spotting
> potential issues.
> 
MTK's mtu3 IP supports at most 5x USB2 phys and 4x USB3 phys. They work
as following:

1. device mode works as HS only:

u2phy0 --- dual-role/OTG

u2phy1 ---|
          +  U3 host-only
u3phy0 ---|

...
u2phy4 ---|
          +  U3 host-only
u3phy3 ---|
(e.g. MT8173 supports 2x u2phys and 1x u3phy, u2phy0 can work as
dual-role mode, u2phy1 & u3phy0 are host-only)

2. device mode works as HS & SS, or host only:

u2phy0 ---|
          + dual-role or host-only
u3phy0 ---|

...
u2phy3 ---|
          + U3 host-only
u3phy3 ---|

u2phy4 --- U2 host-only
(e.g. on MT2701, u2phy0 and u3phy0 work as host-only mode)

mtu3 driver supports host-only, device-only and dual-role mode(use IDDIG
pin), and will take all phys it needed, include host-only phys; 
But if just host-only mode is supported, we can skip mtu3 driver and
make use of xhci-mtk driver directly, then xhci-mtk will take all phys.

> >>
> >> Changes since RFCv1 at [4]:
> >> - split the usb-xhci dt-binding documentation into a separate patch
> >> - fixed a typo ("usb-phy" -> "phys" in the dt-binding example)
> >> - rebased to apply against latest usb-next
> >>
> >>
> >> [0] http://lists.infradead.org/pipermail/linux-amlogic/2017-January/001945.html
> >> [1] http://lists.infradead.org/pipermail/linux-amlogic/2017-January/001947.html
> >> [2] http://lists.infradead.org/pipermail/linux-amlogic/2016-November/001818.html
> >> [3] http://lists.infradead.org/pipermail/linux-amlogic/2017-January/001948.html
> >> [4] http://marc.info/?l=linux-usb&m=148414866303604&w=2
> >>
> >>
> >> Martin Blumenstingl (3):
> >>   dt-bindings: usb: add the documentation for USB root-hub
> >>   usb: host: add a generic platform USB roothub driver
> >>   usb: host: xhci: plat: integrate the platform-roothub
> >>
> >>  .../devicetree/bindings/usb/usb-roothub.txt        |  46 +++++++
> >>  Documentation/devicetree/bindings/usb/usb-xhci.txt |   7 +
> >>  drivers/usb/host/Kconfig                           |   4 +
> >>  drivers/usb/host/Makefile                          |   2 +
> >>  drivers/usb/host/platform-roothub.c                | 146 +++++++++++++++++++++
> >>  drivers/usb/host/platform-roothub.h                |  14 ++
> >>  drivers/usb/host/xhci-plat.c                       |  27 +++-
> >>  drivers/usb/host/xhci.h                            |   2 +
> >>  8 files changed, 247 insertions(+), 1 deletion(-)
> >>  create mode 100644 Documentation/devicetree/bindings/usb/usb-roothub.txt
> >>  create mode 100644 drivers/usb/host/platform-roothub.c
> >>  create mode 100644 drivers/usb/host/platform-roothub.h
> >>
> >
> >
> 
> 
> Regards,
> Martin