39287076e4
musb INDEX register is getting modified/corrupted during temporary
un-locking in a SMP system. Set this register with proper value
after re-acquiring the lock
Scenario:
---------
CPU1 is handling a data transfer completion interrupt received for
the CLASS1 EP
CPU2 is handling a CLASS2 thread which is queuing data to musb for
transfer
Below is the error sequence:
CPU1 | CPU2
--------------------------------------------------------------------
Data transfer completion inter- |
rupt recieved. |
|
musb INDEX reg set to CLASS1 EP |
|
musb LOCK is acquired. |
|
| CLASS2 thread queues data.
|
| CLASS2 thread tries to acquire musb
| LOCK but lock is already taken by
| CLASS1, so CLASS2 thread is
| spinning.
|
From Interrupt Context musb |
giveback function is called |
|
The giveback function releases | CLASS2 thread now acquires LOCK
LOCK |
|
ClASS1 Request's completion cal-| ClASS2 schedules the data transfer and
lback is called | sets the MUSB INDEX to Class2 EP number
|
Interrupt handler for CLASS1 EP |
tries to acquire LOCK and is |
spinning |
|
Interrupt for Class1 EP acquires| Class2 completes the scheduling etc and
the MUSB LOCK | releases the musb LOCK
|
Interrupt for Class1 EP schedul-|
es the next data transfer |
but musb INDEX register is still|
set to CLASS2 EP |
Since the MUSB INDEX register is set to a different endpoint, we
read and modify the wrong registers. Hence data transfer will not
happen properly. This results in unpredictable behavior
So, the MUSB INDEX register is set to proper value again when
interrupt re-acquires the lock
Cc: stable@vger.kernel.org
Signed-off-by: Supriya Karanth <supriya.karanth@stericsson.com>
Signed-off-by: Praveena Nadahally <praveen.nadahally@stericsson.com>
Reviewed-by: srinidhi kasagar <srinidhi.kasagar@stericsson.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.