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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [MirageOS-devel] Writing to Multiple Serial Ports
Anil, On 10/7/2015 12:36 PM, Anil Madhavapeddy wrote: > On 7 Oct 2015, at 15:53, Paul Skentzos <paul.skentzos@xxxxxxxxxxxxxxx> wrote: >> >> Hi Luke, >> >> On 10/7/2015 10:15 AM, Luke Dunstan wrote: >>> Hi Paul, >>> >>> Did you get serial ports working even in dom0 on Cubietruck yet? It took me >>> quite a while to discover that Xen normally disables the A20 UARTs by >>> deleting >>> them from the device tree: >>> >>> http://xenbits.xen.org/gitweb/?p=xen.git;a=blob;f=xen/arch/arm/platforms/sunxi.c;h=0ba7b3d9b476a95edb653e120b7b3900a47f7c06;hb=HEAD#l64 >>> >>> Luke >>> >> >> Yes, we do have this working. It was a bit of an annoyance that we discovered >> just as you did when starting to work on the Cubietruck. >> >> We found that all serial ports with the "snps,dw-apb-uart" driver are >> blacklisted on the "sunxi" platform to prevent dom0 from having driver >> access to >> the Xen console. So we hacked up the attached patch. Which is not an ideal >> fix, but it was good enough for now. >> >> The better fix would be to have Xen compare the memory address for every >> item in >> the device tree against the addresses that Xen has already reserved for >> itself. > > We could apply this patch to the https://github.com/mirage/xen-arm-builder > distribution, which is only really used to boot on Cubieboards at the moment. > It's nice to have the out-of-the-box experience just work for that > distribution. > > -anil > > I agree! Would you apply the patch as is or would you like us to formally submit the patch through the mailing list? - Paul > >> >> - Paul >> >>> >>> On Wed, 7 Oct 2015 at 21:00 Paul Skentzos <paul.skentzos@xxxxxxxxxxxxxxx >>> <mailto:paul.skentzos@xxxxxxxxxxxxxxx>> wrote: >>> >>> Dave, >>> >>> >>> On 10/6/2015 5:04 PM, David Scott wrote: >>>> Hi Paul, Aaron, >>>> >>>> On Tue, Oct 6, 2015 at 8:27 PM, Paul Skentzos >>> <paul.skentzos@xxxxxxxxxxxxxxx <mailto:paul.skentzos@xxxxxxxxxxxxxxx> >>>> <mailto:paul.skentzos@xxxxxxxxxxxxxxx >>> <mailto:paul.skentzos@xxxxxxxxxxxxxxx>>> wrote: >>>> >>>> We are trying to access a serial port passed to a domu. We're very new >>> to Mirage >>>> and ocaml, but plan on converting our existing system to use MirageOS >>>> for >>>> various domU's. >>>> >>>> So, at the moment, the question we have is whether anyone has had any >>> success >>>> writing to multiple serial ports with one of those serial ports being >>> accessed >>>> from a domu? >>>> >>>> As a first attempt, we took the Mirage console example and added a >>>> second >>>> console. We connected it to '1' and then to /dev/null and tried to >>> print to it. >>>> Neither of the ideas were valid. We're not sure what the console >>> should be named >>>> or what the hashtbl is looking for. The application compiles, but the >>> VM halts >>>> with a message stating. "... waiting for hotplug". The application >>> built for >>>> unix didn't work either. >>>> >>>> >>>> We are trying to read data from a GPS receiver from a domu. >>>> >>>> >>>> Interesting! Is the GPS receiver connected to a physical serial port on >>> the host? >>>> >>> >>> Thanks for the quick response. Yes, the GPS is connected to the host, to >>> a >>> hardware serial port. >>> >>>> The virtual serial ports that Mirage can see need to be served by >>>> something on >>>> the host (a "backend", typically in dom0). If you're creating your VM with >>>> "xl >>>> create" then you can declare "channels"[1] which will spawn a qemu process >>>> in >>>> dom0 which will act as the server/backend. At the moment the backend can >>> only be >>>> connected to a fresh tty or a Unix domain socket -- there is no built-in >>> support >>>> for proxying to a real /dev/ttyS* device. >>>> >>>> I think the first thing to do is to verify that adding a 'channel' to your >>>> xl >>>> config file causes the Xen domU to get further than "waiting for hotplug". >>> After >>>> that I think you could declare the backend to be a Unix domain socket, and >>> then >>>> run a proxy in dom0 which would write the data to the appropriate ttyS >>>> device. >>>> >>>> Sorry that's a bit clunky -- when I added the channel support to "xl" I >>>> didn't >>>> think about the possibility of a real serial port. I'm sure that could be >>> added >>>> in future though. >>>> >>>> What do you think? >>>> >>> >>> This is really good information and you were speaking the language my >>> colleague >>> and I were as we iterated through the design. >>> >>> Here are our results. Running the system on an x86 VM worked just as you >>> described above, so that was great news. However, and we should have >>> been clear >>> about this at the beginning, our hardware platform is ARM based; >>> Cubietruck, >>> specifically. We tried the same process on the Cubietruck and it did not >>> work. >>> I'm assuming that this is the case since ARM does not make use of qemu >>> like x86 >>> does. >>> >>> It seems that this could be overcome on ARM, however not without some >>> difficulty. Any thoughts on this? >>> >>> Best regards, >>> Paul >>> >>> >>>> Cheers, >>>> Dave Scott >>>> >>>> [1] http://xenbits.xen.org/docs/unstable/misc/channel.txt >>>> >>>> >>>> Any ideas where we should look for getting this capability? >>>> >>>> I appreciate the help! >>>> >>>> Paul Skentzos >>>> Aaron Cornelius >>>> >>>> >>>> >>>> >>>> >>>> _______________________________________________ >>>> MirageOS-devel mailing list >>>> MirageOS-devel@xxxxxxxxxxxxxxxxxxxx >>> <mailto:MirageOS-devel@xxxxxxxxxxxxxxxxxxxx> >>> <mailto:MirageOS-devel@xxxxxxxxxxxxxxxxxxxx >>> <mailto:MirageOS-devel@xxxxxxxxxxxxxxxxxxxx>> >>>> http://lists.xenproject.org/cgi-bin/mailman/listinfo/mirageos-devel >>>> >>>> >>>> >>>> >>>> -- >>>> Dave Scott >>> >>> _______________________________________________ >>> MirageOS-devel mailing list >>> MirageOS-devel@xxxxxxxxxxxxxxxxxxxx >>> <mailto:MirageOS-devel@xxxxxxxxxxxxxxxxxxxx> >>> http://lists.xenproject.org/cgi-bin/mailman/listinfo/mirageos-devel >>> >> <0001-Fix-blacklist-for-Cubie-UARTs.patch>_______________________________________________ >> MirageOS-devel mailing list >> MirageOS-devel@xxxxxxxxxxxxxxxxxxxx >> http://lists.xenproject.org/cgi-bin/mailman/listinfo/mirageos-devel > _______________________________________________ MirageOS-devel mailing list MirageOS-devel@xxxxxxxxxxxxxxxxxxxx http://lists.xenproject.org/cgi-bin/mailman/listinfo/mirageos-devel
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