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Message-ID: <20150826061950.GB6435@shlinux2> Date: Wed, 26 Aug 2015 14:19:51 +0800 From: Peter Chen <peter.chen@...escale.com> To: Roger Quadros <rogerq@...com> CC: <stern@...land.harvard.edu>, <balbi@...com>, <gregkh@...uxfoundation.org>, <dan.j.williams@...el.com>, <jun.li@...escale.com>, <mathias.nyman@...ux.intel.com>, <tony@...mide.com>, <Joao.Pinto@...opsys.com>, <abrestic@...omium.org>, <linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>, <linux-omap@...r.kernel.org> Subject: Re: [PATCH v4 00/13] USB: OTG/DRD Core functionality On Mon, Aug 24, 2015 at 04:21:11PM +0300, Roger Quadros wrote: > Hi, > > This series centralizes OTG/Dual-role functionality in the kernel. > As of now I've got Dual-role functionality working pretty reliably on > dra7-evm and am437x-gp-evm. > > DWC3 controller and platform related patches will be sent separately. > I will review this patch set after you send the above, it will be more clear if there are users for code. Peter > Series is based on Greg's usb-next tree. > > Changelog: > --------- > v4: > - Added DT support for tying otg-controller to host and gadget > controllers. For DT we no longer have the constraint that > OTG controller needs to be parent of host and gadget. They can be > tied together using the "otg-controller" property. > - Relax the requirement for DT case that otg controller must register before > host/gadget. We maintain a wait list of host/gadget devices > waiting on the otg controller. > - Use a single struct usb_otg for otg data. > - Don't override host/gadget start/stop APIs. Let the controller > drivers do what they want as they know best. Helper API is provided > for controller start/stop that controller driver can use. > - Introduce struct usb_otg_config to pass the otg capabilities, > otg ops and otg timer timeouts during otg controller registration. > - rebased on Greg's usb.git/usb-next > > v3: > - all otg related definations now in otg.h > - single kernel config USB_OTG to enable OTG core and FSM. > - resolved symbol dependency issues. > - use dev_vdbg instead of VDBG() in usb-otg-fsm.c > - rebased on v4.2-rc1 > > v2: > - Use add/remove_hcd() instead of start/stop_hcd() to enable/disable > the host controller > - added dual-role-device (DRD) state machine which is a much simpler > mode of operation when compared to OTG. Here we don't support fancy > OTG features like HNP, SRP, on the fly role-swap. The mode of operation > is determined based on ID pin (cable type) and the role doesn't change > till the cable type changes. > > Why?: > ---- > > Most of the OTG drivers have been dealing with the OTG state machine > themselves and there is a scope for code re-use. This has been > partly addressed by the usb/common/usb-otg-fsm.c but it still > leaves the instantiation of the state machine and OTG timers > to the controller drivers. We re-use usb-otg-fsm.c but > go one step further by instantiating the state machine and timers > thus making it easier for drivers to implement OTG functionality. > > Newer OTG cores support standard host interface (e.g. xHCI) so > host and gadget functionality are no longer closely knit like older > cores. There needs to be a way to co-ordinate the operation of the > host and gadget in OTG mode. i.e. to stop and start them from a > central location. This central location should be the USB OTG core. > > Host and gadget controllers might be sharing resources and can't > be always running. One has to be stopped for the other to run. > This can't be done as of now and can be done from the OTG core. > > What?: > ----- > > The OTG core instantiates the OTG/DRD Finite State Machine > per OTG controller and manages starting/stopping the > host and gadget controllers based on the bus state. > > It provides APIs for the following > > - Registering an OTG capable controller > struct otg_fsm *usb_otg_register(struct device *dev, > struct usb_otg_config *config); > > int usb_otg_unregister(struct device *dev); > > - Registering Host controllers to OTG core (used by hcd-core) > int usb_otg_register_hcd(struct usb_hcd *hcd, unsigned int irqnum, > unsigned long irqflags, struct otg_hcd_ops *ops); > int usb_otg_unregister_hcd(struct usb_hcd *hcd); > > > - Registering Gadget controllers to OTG core (used by udc-core) > int usb_otg_register_gadget(struct usb_gadget *gadget, > struct otg_gadget_ops *ops); > int usb_otg_unregister_gadget(struct usb_gadget *gadget); > > > - Providing inputs to and kicking the OTG state machine > void usb_otg_sync_inputs(struct otg_fsm *fsm); > int usb_otg_kick_fsm(struct device *hcd_gcd_device); > > - Getting controller device structure from OTG state machine instance > struct device *usb_otg_fsm_to_dev(struct otg_fsm *fsm); > > 'struct otg_fsm' is the interface to the OTG state machine. > It contains inputs to the fsm, status of the fsm and operations > for the OTG controller driver. > > - Helper APIs for starting/stopping host/gadget controllers > int usb_otg_start_host(struct otg_fsm *fsm, int on); > int usb_otg_start_gadget(struct otg_fsm *fsm, int on); > > Usage model: > ----------- > > - The OTG core needs to know what host and gadget controllers are > linked to the OTG controller. For DT boots we can provide that > information by adding "otg-controller" property to the host and > gadget controller nodes that points to the right otg controller. > For legacy boot we assume that OTG controller is the parent > of the host and gadget controllers. For DT if "otg-controller" > property is not present then parent child relationship constraint > applies. > > - The OTG controller driver must call usb_otg_register() to register > itself with the OTG core. It must also provide the required > OTG configuration, fsm operations and timer timeouts (optional) > via struct usb_otg_config. The fsm operations will be called > depending on the OTG bus state. > > - The host/gadget core stacks are modified to inform the OTG core > whenever a new host/gadget device is added. The OTG core then > checks if the host/gadget is part of the OTG controller and if yes > then prevents the host/gadget from starting till both host and > gadget are registered, OTG state machine is running and the > USB bus state is appropriate to start host/gadget. > For this, APIs have been added to host/gadget stacks to start/stop > the controllers from the OTG core. > For DT boots, If the OTG controller hasn't yet been registered > while the host/gadget are added, the OTG core will hold it in a wait list > and register them when the OTG controller registers. > > - No modification is needed for the host/gadget controller drivers. > They must ensure that their start/stop methods can be called repeatedly > and any shared resources between host & gadget are properly managed. > The OTG core ensures that both are not started simultaneously. > > - The OTG core instantiates one OTG state machine per OTG controller > and the necessary OTG timers to manage OTG state timeouts. > If none of the otg features are set during usb_otg_register() then it > instanciates a DRD (dual-role device) state machine instead. > The state machine is started when both host & gadget register and > stopped when either of them unregisters. The controllers are started > and stopped depending on bus state. > > - During the lifetime of the OTG state machine, inputs can be > provided to it by modifying the appropriate members of 'struct otg_fsm' > and calling usb_otg_sync_inputs(). This is typically done by the > OTG controller driver that called usb_otg_register(). > > -- > cheers, > -roger > > Roger Quadros (13): > usb: otg-fsm: Add documentation for struct otg_fsm > usb: otg-fsm: support multiple instances > usb: otg-fsm: Prevent build warning "VDBG" redefined > otg-fsm: move usb_bus_start_enum into otg-fsm->ops > usb: hcd.h: Add OTG to HCD interface > usb: gadget.h: Add OTG to gadget interface > usb: otg: add OTG core > usb: doc: dt-binding: Add otg-controller property > usb: chipidea: move from CONFIG_USB_OTG_FSM to CONFIG_USB_OTG > usb: hcd: Adapt to OTG core > usb: core: hub: Notify OTG fsm when A device sets b_hnp_enable > usb: gadget: udc: adapt to OTG core > usb: otg: Add dual-role device (DRD) support > > Documentation/devicetree/bindings/usb/generic.txt | 5 + > Documentation/usb/chipidea.txt | 2 +- > MAINTAINERS | 4 +- > drivers/usb/Kconfig | 2 +- > drivers/usb/Makefile | 1 + > drivers/usb/chipidea/Makefile | 2 +- > drivers/usb/chipidea/ci.h | 2 +- > drivers/usb/chipidea/otg_fsm.c | 1 + > drivers/usb/chipidea/otg_fsm.h | 2 +- > drivers/usb/common/Makefile | 3 +- > drivers/usb/common/usb-otg-fsm.c | 26 +- > drivers/usb/common/usb-otg.c | 1223 +++++++++++++++++++++ > drivers/usb/common/usb-otg.h | 71 ++ > drivers/usb/core/Kconfig | 11 +- > drivers/usb/core/hcd.c | 55 +- > drivers/usb/core/hub.c | 10 +- > drivers/usb/gadget/udc/udc-core.c | 124 ++- > drivers/usb/phy/Kconfig | 2 +- > drivers/usb/phy/phy-fsl-usb.c | 3 + > include/linux/usb/gadget.h | 14 + > include/linux/usb/hcd.h | 14 + > include/linux/usb/otg-fsm.h | 116 +- > include/linux/usb/otg.h | 191 +++- > 23 files changed, 1808 insertions(+), 76 deletions(-) > create mode 100644 drivers/usb/common/usb-otg.c > create mode 100644 drivers/usb/common/usb-otg.h > > -- > 2.1.4 > -- Best Regards, Peter Chen -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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