Hi Frieder, > Subject: Race condition between Linux and M4 app with rpmsg link init > > Hi, > > I have a problem with a kind of race condition between Linux > remoteproc/rpmsg on the A53 core and the app on the M4 core when > starting the remote core and initializing the rpmsg link. This is what > happens: > > | A53 | M4 | > | ---------------------------- | --------------------------- | > | * load the ELF file | | > | * start the M4 core | | > | rproc_start() | | > | imx_rproc_start() | | > | | * M4 app starts | > | rproc_start_subdevices() | | > | | * M4 receives mailbox IRQ | > | | * M4 app doesn't handle | > | | IRQ as they are not | > | | registered yet | > | | * M4 registers IRQ handlers | > > > When I add a delay in rproc_start() between the calls to > imx_rproc_start() and rproc_start_subdevices() this give the M4 app enough > time to fully start and register the IRQ handlers. In this case the rpmsg link is > initialized correctly. > > What is the proper way to fix this? Is there already a mechanism to handle > such cases? I had patches [1], but those were rejected. I not find proper way to address the issue in upstream kernel. [1] https://lore.kernel.org/lkml/20221104153303.GB1873068@p14s/t/#md0c56e96f61f6a423852ae697147d0394c7f0367 Regards, Peng. > > Thanks for any help! > > Best regards > Frieder
