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Date: Wed, 18 Mar 2015 10:37:26 -0700 From: Tony Lindgren <tony@...mide.com> To: Roger Quadros <rogerq@...com> Cc: gregkh@...uxfoundation.org, balbi@...com, stern@...land.harvard.edu, dan.j.williams@...el.com, peter.chen@...escale.com, jun.li@...escale.com, mathias.nyman@...ux.intel.com, linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org, linux-omap@...r.kernel.org Subject: Re: [RFC][PATCH 0/9] USB: OTG Core functionality * Roger Quadros <rogerq@...com> [150318 07:00]: > Hi, > > [NOTE: RFC only. Not for merge yet.] > > This is an attempt to centralize OTG functionality in the kernel. > Still work in progress but I wanted to get an early feedback > to avoid major rework. :) > > 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 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 *parent_dev, > struct otg_fsm_ops *fsm_ops); > int usb_otg_unregister(struct device *parent_dev); > > - Registering Host controllers to OTG core (used by hcd-core) > int usb_otg_register_hcd(struct usb_hcd *hcd); > 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); > 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); > > '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. Sounds good to me. I take you're also planning to provide some common /sys/kernel/debug/otg type interfaces for OTG validation tests? For things like SRP etc. Regards, Tony > Usage model: > ----------- > > - The OTG controller device is assumed to be the parent of > the host and gadget controller. It must call usb_otg_register() > before populating the host and gadget devices so that the OTG > core is aware that it is an OTG device before the host & gadget > register. The OTG controller must provide struct otg_fsm_ops * > which will be called by the OTG core depending on 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. > > - 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. > 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() since it is > the only external component that has the 'struct otg_fsm' handle. > > Pending items: > - We probably need a otg class. > - sysfs interface for application OTG inputs and OTG status information > - resolve symbol dependency for module use. > - otg driver for dwc3 core to get dual-role working on dra7-evm. > > cheers, > -roger > > Roger Quadros (9): > usb: hcd: Introduce usb_start/stop_hcd() > usb: gadget: add usb_gadget_start/stop() > usb: otg: add OTG core > usb: otg: hub: Notify OTG fsm when A device sets b_hnp_enable > usb: hcd: adapt to OTG > usb: gadget: udc: adapt to OTG > usb: dwc3: adapt to OTG core > usb: otg-fsm: Remove unused members in struct otg_fsm > usb: otg-fsm: Add documentation for struct otg_fsm > > drivers/usb/Makefile | 1 + > drivers/usb/common/Makefile | 1 + > drivers/usb/common/usb-otg.c | 732 ++++++++++++++++++++++++++++++++++++++ > drivers/usb/common/usb-otg.h | 71 ++++ > drivers/usb/core/Kconfig | 8 + > drivers/usb/core/hcd.c | 153 +++++--- > drivers/usb/core/hub.c | 11 +- > drivers/usb/dwc3/core.c | 101 ++++++ > drivers/usb/dwc3/core.h | 6 + > drivers/usb/dwc3/platform_data.h | 1 + > drivers/usb/gadget/udc/udc-core.c | 172 ++++++++- > include/linux/usb/gadget.h | 3 + > include/linux/usb/hcd.h | 2 + > include/linux/usb/otg-fsm.h | 81 ++++- > include/linux/usb/usb-otg.h | 86 +++++ > 15 files changed, 1357 insertions(+), 72 deletions(-) > create mode 100644 drivers/usb/common/usb-otg.c > create mode 100644 drivers/usb/common/usb-otg.h > create mode 100644 include/linux/usb/usb-otg.h > > -- > 2.1.0 > > -- > 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/ -- 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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