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This patch supports the retention and offmode support in the idle path for musb driver using runtime pm APIs. This is restricted to support offmode and retention only when device not connected.When device/cable connected with gadget driver loaded,configured to no idle/standby which will not allow the core transition to retention or off. There is no context save/restore done by hardware for musb in OMAP3 and OMAP4,driver has to take care of saving and restoring the context during offmode. Musb has a requirement of configuring sysconfig register to force idle/standby mode and set the ENFORCE bit in module STANDBY register for retention and offmode support. Runtime pm and hwmod frameworks will take care of configuring to force idle/standby when pm_runtime_put_sync is called and back to no idle/standby when pm_runeime_get_sync is called. Compile, boot tested and also tested the retention in the idle path on OMAP3630Zoom3. And tested the global suspend/resume with offmode enabled. Usb basic functionality tested on OMAP4430SDP. There is some problem with idle path offmode in mainline, I could not test with offmode. But I have tested this patch with resetting the controller in the idle path when wakeup from retention just to make sure that the context is lost, and restore path is working fine. Removed .suspend/.resume fnction pointers and functions because there is no need of having these functions as all required work is done at runtime in the driver. There is no need to call the runtime pm api with glue driver device as glue layer device is the parent of musb core device, when runtime apis are called for the child, parent device runtime functionality will be invoked. Design overview: pm_runtime_get_sync: When called with musb core device takes care of enabling the clock, calling runtime callback function of omap2430 glue layer, runtime call back of musb driver and configure the musb sysconfig to no idle/standby pm_runtime_put: Takes care of calling runtime callback function of omap2430 glue layer, runtime call back of musb driver, Configure the musb sysconfig to force idle/standby and disable the clock. During musb driver load: Call pm_runtime_get_sync. End of musb driver load: Call pm_runtime_put During gadget driver load: Call pm_runtime_get_sync, End of gadget driver load: Call pm_runtime_put if there is no device or cable is connected. During unload of the gadget driver:Call pm_runtime_get_sync if cable/device is not connected. End of the gadget driver unload : pm_runtime_put During unload of musb driver : Call pm_runtime_get_sync End of unload: Call pm_runtime_put On connect of usb cable/device -> transceiver notification(VBUS and ID-GND): pm_runtime_get_sync only if the gadget driver loaded. On disconnect of the cable/device -> Disconnect Notification: pm_runtime_put if the gadget driver is loaded. Signed-off-by: Hema HK <hemahk@ti.com> Signed-off-by: Felipe Balbi <balbi@ti.com>
To understand all the Linux-USB framework, you'll use these resources:
* This source code. This is necessarily an evolving work, and
includes kerneldoc that should help you get a current overview.
("make pdfdocs", and then look at "usb.pdf" for host side and
"gadget.pdf" for peripheral side.) Also, Documentation/usb has
more information.
* The USB 2.0 specification (from www.usb.org), with supplements
such as those for USB OTG and the various device classes.
The USB specification has a good overview chapter, and USB
peripherals conform to the widely known "Chapter 9".
* Chip specifications for USB controllers. Examples include
host controllers (on PCs, servers, and more); peripheral
controllers (in devices with Linux firmware, like printers or
cell phones); and hard-wired peripherals like Ethernet adapters.
* Specifications for other protocols implemented by USB peripheral
functions. Some are vendor-specific; others are vendor-neutral
but just standardized outside of the www.usb.org team.
Here is a list of what each subdirectory here is, and what is contained in
them.
core/ - This is for the core USB host code, including the
usbfs files and the hub class driver ("khubd").
host/ - This is for USB host controller drivers. This
includes UHCI, OHCI, EHCI, and others that might
be used with more specialized "embedded" systems.
gadget/ - This is for USB peripheral controller drivers and
the various gadget drivers which talk to them.
Individual USB driver directories. A new driver should be added to the
first subdirectory in the list below that it fits into.
image/ - This is for still image drivers, like scanners or
digital cameras.
../input/ - This is for any driver that uses the input subsystem,
like keyboard, mice, touchscreens, tablets, etc.
../media/ - This is for multimedia drivers, like video cameras,
radios, and any other drivers that talk to the v4l
subsystem.
../net/ - This is for network drivers.
serial/ - This is for USB to serial drivers.
storage/ - This is for USB mass-storage drivers.
class/ - This is for all USB device drivers that do not fit
into any of the above categories, and work for a range
of USB Class specified devices.
misc/ - This is for all USB device drivers that do not fit
into any of the above categories.