[PATCH v4 0/3] initialize (multiple) PHYs in xhci-plat

Martin Blumenstingl martin.blumenstingl at googlemail.com
Sun Sep 17 13:51:31 PDT 2017

Hello Mathias, Hello Greg,

On Sun, Sep 3, 2017 at 11:38 PM, Martin Blumenstingl
<martin.blumenstingl at googlemail.com> 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).
> Changes since RFCv3 at [6]:
> - moved the DT binding change from patch #3 to patch #1 as suggested
>   by Rob Herring (and slightly adjusted the commit message to account
>   for that)
> - added Tested-by from Chunfeng Yun (who confirmed that the whole
>   concept and implementation works fine on Mediatek SoCs - many thanks
>   again!) to patch #2
> - added Rob Herring's ACK to patches 1 and 3
> - dropped RFC status (RFCv3 -> PATCH v4)
I just wanted to rebase this to v4.14-rc1 (now that this is out) -
however I noticed that v4 still applies to v4.14-rc1 cleanly (the
patches are still identical to v4 after rebasing).

we have an ACK from the devicetree maintainers and a "Tested-by" for a
Mediatek (= non-Amlogic) SoC.
I already have patches for the Amlogic GXL/GXM platforms queued, those
are just waiting on this series.

what is still missing to get this series into v4.15?

> Changes since RFCv2 at [5]:
> - split phy_{init,exit} and phy_power_{on,off} handling. up until RFCv2
>   I called phy_init plus phy_power_on in platform_roothub_power_on and
>   phy_power_off plus phy_exit in platform_roothub_power_off. However,
>   Chunfeng Yun (a Mediatek SoC developer - many thanks for testing my
>   series and providing great feedback) reported that only using
>   phy_power_off (and omitting phy_exit) during system suspend fixes an
>   issue where USB devices would be re-enumerated when resuming. His
>   original problem description: "In order to keep link state on mt8173,
>   we just power off all phys(not exit) when system enter suspend, then
>   power on them again (needn't init, otherwise device will be
>   disconnected) when system resume, this can avoid re-enumerating
>   device.". This fix affects patch #2 and #3 as we now have
>   platform_roothub_init (which calls phy_init internally),
>   platform_roothub_power_on (which calls phy_power_on internally),
>   platform_roothub_power_off (which calls phy_power_off internally) and
>   platform_roothub_exit (which calls phy_exit internally). suspend and
>   resume only call platform_roothub_power_{on,off} to prevent the issue
>   described by Chunfeng Yun (unfortunately I cannot test this because
>   the Amlogic platform currently does not support system suspend).
> - dropped two struct forward declarations from platform-roothub.h which
>   are not used in the header file (thanks to Chunfeng Yun for spotting
>   this)
> 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
> [5] https://www.spinics.net/lists/linux-usb/msg158967.html
> [6] https://www.spinics.net/lists/devicetree/msg190426.html
> 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                | 180 +++++++++++++++++++++
>  drivers/usb/host/platform-roothub.h                |  12 ++
>  drivers/usb/host/xhci-plat.c                       |  35 +++-
>  drivers/usb/host/xhci.h                            |   2 +
>  8 files changed, 286 insertions(+), 2 deletions(-)
>  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
> --
> 2.14.1

Have a great week!

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