On Fri, Feb 17, 2012 at 02:54:52PM +0530, Praveena Nadahally wrote: > From: Supriya Karanth <supriya.karanth@xxxxxxxxxxxxxx> > > 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 > > Signed-off-by: Supriya Karanth <supriya.karanth@xxxxxxxxxxxxxx> > Signed-off-by: Praveena Nadahally <praveen.nadahally@xxxxxxxxxxxxxx> > Reviewed-by: srinidhi kasagar <srinidhi.kasagar@xxxxxxxxxxxxxx> > --- applied, thanks -- balbi
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