On Mon, Dec 07, 2020 at 06:42:07PM +0000, Daniele Alessandrelli wrote: > Hi Rob, > > Thanks for the feedback. > > On Mon, 2020-12-07 at 10:01 -0600, Rob Herring wrote: > > On Tue, Dec 01, 2020 at 02:34:51PM -0800, mgross@xxxxxxxxxxxxxxx wrote: > > > From: Daniele Alessandrelli <daniele.alessandrelli@xxxxxxxxx> > > > > > > Add DT binding documentation for the Intel Keem Bay IPC driver, which > > > enables communication between the Computing Sub-System (CSS) and the > > > Multimedia Sub-System (MSS) of the Intel Movidius SoC code named Keem > > > Bay. > > > > > [cut] > > > > + > > > +description: > > > + The Keem Bay IPC driver enables Inter-Processor Communication (IPC) with the > > > + Visual Processor Unit (VPU) embedded in the Intel Movidius SoC code named > > > + Keem Bay. > > > > Sounds like a mailbox. > > We did consider using the mailbox framework, but eventually decided > against it; mainly because of the following two reasons: > > 1. The channel concept in the Mailbox framework is different than the > channel concept in Keem Bay IPC: > > a. My understanding is that Mailbox channels are meant to be SW > representation of physical HW channels, while in Keem Bay IPC > channels are software abstractions to achieve communication > multiplexing over a single HW link > > b. Additionally, Keem Bay IPC has two different classes of channels > (high-speed channels and general-purpose channels) that need to > access the same HW link with different priorities. > > 2. The blocking / non-blocking TX behavior of mailbox channels is > defined at channel creation time (by the tx_block value of the > mailbox client passed to mbox_request_channel(); my understanding > is that the tx_block value cannot be modified after the channel is > created), while in Keem Bay IPC the same channel can be used for > both blocking and non-blocking TX (behavior is controlled by the > timeout argument passed to keembay_ipc_send()). > > Having said that, I guess that it could be possible to create a Mailbox > driver implementing the core communication mechanism used by the Keem > Bay IPC and then build our API around it (basically having two > drivers). But I'm not sure that would make the code simpler or easier > to maintain. Any thoughts on this? The use of the mailbox binding and the kernel's mailbox framework are independent questions. I'm only concerned with the former (for purposes of this review). Rob
