On Thu, May 22, 2014 at 04:27:05PM +0100, Srinivas Kandagatla wrote: <snip> > > > >The EOT is not used for every transaction. It is part of a handshaking > >protocol with the attached peripheral, much like the NWD (notify when done). As > >near as I can tell today, no peripheral depends on the EOB, so we could drop it > >for now until it is needed and cross this bridge when we need to. > > As EOT behaviour is totally dependent on the attached peripheral(or > channel), Can't we make this specific to channel by passing > additional flags in the DT dma channel descriptors? This will be > better abstraction for drivers as well. Even for channels where you want to use EOT, you don't use it for every transaction. So a global channel flag isn't going to work. This is the same for NWD. It is a per descriptor choice. > > I know that EOT flag is part of descriptor but still some channels > *must* have EOT to run there state-machine correctly. So making it > optional for those channels might be wrong. > > Are there any use cases for particular *channel* where EOT > requirement changes dynamically? I2C is one example. You place EOT on the last transaction that makes up a write/read transaction. You may have multiple descriptors to send data, but the last one has EOT. And for read transactions, you place NWD on the last read transaction. <snip> -- sent by an employee of the Qualcomm Innovation Center, Inc. The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, hosted by The Linux Foundation -- To unsubscribe from this list: send the line "unsubscribe dmaengine" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
