Subject: Re: [PATCH V2 0/4] misc: xgene: Add support for APM X-Gene SoC Queue Manager/Traffic Manager

From: Greg KH <[email-masked]>
Date: Sun, 5 Jan 2014 10:01:22 -0800

On Sat, Jan 04, 2014 at 09:39:08PM -0800, Loc Ho wrote:
> Hi,
> 
> >> >> >> 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
> >
> > There is nothing at this link :(
> 
> I tried click on the txt file link from web site
> http://www.spinics.net/lists/netdev/msg264628.html and don't see any
> problem with accessing the txt file.

Now it's working :)

Anyway, as this is a .txt file, why wasn't it just sent in email, and
added to the patch series as a documentation file?

thanks,

greg k-h
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