On Sat, Dec 21, 2013 at 11:03 PM, Arnd Bergmann <arnd@xxxxxxxx> wrote: > On Saturday 21 December 2013 17:00:51 Loc Ho wrote: >> On Sat, Dec 21, 2013 at 12:11 PM, Arnd Bergmann <arnd@xxxxxxxx> wrote: >> > On Saturday 21 December 2013, Ravi Patel wrote: >> >> This patch adds support for APM X-Gene SoC Queue Manager/Traffic Manager. >> >> QMTM is required by APM X-Gene SoC Ethernet, PktDMA (XOR Engine) and >> >> Security Engine subsystems. All subsystems communicate with QMTM using >> >> messages which include information about the work to be performed and >> >> the location of associated data buffers. >> > >> > Please describe here what the purpose of the qmtm is, as this is not >> > entirely clear from the code. >> > >> > In particular, please describe how this differs from a dmaengine driver >> > and why it is not possible to extend the dma slave API to describe qmtm >> > as a dma engine. >> > >> [Loc Ho] >> If the QM driver implements the DMA API, what about the actual DMA >> engine driver which interfaces with this QM driver. We would have DMA >> client interfaces with the X-Gene DMA driver (not available yet) via >> DMA API which in turn interfaces with this QM driver via DMA API. >> Won't this be kind of awkward? Also, the QM only manage messages (or >> descriptors) which are 32-bytes or 64-bytes. It doesn't actually do >> any data transfer of various sizes. > > Please describe here what the purpose of the qmtm is, as this is not > entirely clear from the code or from your reply. > > Greg was guessing that it's a bus controller, my best guess is a DMA > engine. If it's something completely different, you have to let > us know what it is so we can do a proper review rather than guessing. > > Please provide a link to the data sheet if you are unable to explain. Here is URL to a text document explaining role of QMTM device with CPU, Ethernet subsystem. https://drive.google.com/file/d/0B28TgQZ3JLoRRGNnbjJoUGNHWW8/edit?usp=sharing For simplicity, I have shown only Ethernet. PktDMA and Security subsystem interfaces with QMTM in the same way as Ethernet. -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
