0f901c9801
According to the comments, we rely on the OTG timer because the core does not expose some important OTG details. So far this is all I know. After playing with OTG I stumbled over a problem: musb is recognized as a B-device without a problem. Whenever a cable is plugged, the VBUS rises, musb recognizes this as a starting session, sets the MUSB_DEVCTL_SESSION bit by itself and a RESET interrupt occurs, the session starts. Good. After a disconnect, the timer is started and re-starts itself because it remains in B_IDLE with the BDEVICE set. I didn't figure the the reason or the need for it. Nothing changes here except for OTG state from B to A device if the BDEVICE bit disappears. This doesn't make much sense to me because nothing happens after this. _IF_ we receive an interrupt before the state change then we may act on wrong condition. Plugging a B-device (and letting MUSB act as host) doesn't work here. The reason seems to be that the MUSB tries to start a session, it fails and then it removes the bit. So we never start as a host. This patch sets the MUSB_DEVCTL_SESSION bit in the IDLE state so musb can try to establish a session as host. After the bit is set, musb tries to start a session and if it fails it clears the bit. Therefore it will try over and over again until a session either as host or as device is established. The readout of the MUSB_DEVCTL register after the removal the MUSB_DEVCTL_SESSION (in A_WAIT_BCON) has been removed because it did not contain the BDEVICE bit set (in the second read) leading to A_IDLE. After plugging a host musb assumed that it is also a host and complained about a missing reset. However a third read of the register has has the BDEVICE bit set so it seems that it is not stable. This mostly what da8xx.c is doing except that we set the timer also after A_WAIT_BCON so the session bit can be triggered. Whit this change I was able to keep am335x-evm in OTG mode and plug in either a HOST or a DEVICE and in a random order and the device was recognized. Cc: stable@vger.kernel.org # v3.11 Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Felipe Balbi <balbi@ti.com> |
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| c67x00 | ||
| chipidea | ||
| class | ||
| core | ||
| dwc3 | ||
| early | ||
| gadget | ||
| host | ||
| image | ||
| misc | ||
| mon | ||
| musb | ||
| phy | ||
| renesas_usbhs | ||
| serial | ||
| storage | ||
| wusbcore | ||
| Kconfig | ||
| Makefile | ||
| README | ||
| usb-common.c | ||
| usb-skeleton.c | ||
README
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.