Re: [MirageOS-devel] Writing to Multiple Serial Ports

[Anil Madhavapeddy <anil@xxxxxxxxxx>]

> On 23 Oct 2015, at 20:24, Paul Skentzos <Paul.Skentzos@xxxxxxxxxxxxxxx> wrote:
> 
> On 10/20/2015 1:52 PM, Anil Madhavapeddy wrote:
>> 
>>> On 7 Oct 2015, at 18:25, Paul Skentzos <Paul.Skentzos@xxxxxxxxxxxxxxx> 
>>> wrote:
>>> 
>>> 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?
>> 
>> Hi Paul,
>> 
>> The best way to get the patch into the repository is by submitting a GitHub 
>> Pull Request.  This ensures that the provenance of the patch is tracked 
>> correctly as coming from you in the history (we can do this via the mailing 
>> list as well, but the web interface is easier).
>> 
>> The relevant scripts in there that clone and build xen are in 
>> https://github.com/mirage/xen-arm-builder in the clone-repos.sh script and 
>> then build-xen.sh.  You can either apply the patch above in this repo 
>> directly if you wish.
>> 
>> Let me know if you have any questions about the GitHub PR process.
>> 
>> regards,
>> Anil
>> 
> 
> Anil,
> 
> We've sent a pull request to the https://github.com/mirage/xen-arm-builder 
> repo
> from https://github.com/dornerworks/xen-arm-builder. Let us know if things 
> look
> OK and if there is anything else we need to do to close it out from our end.

Thanks Paul -- the PR is fine.  We don't entirely have an "owner" for this 
particular distribution yet, so I've got it on my queue to look at the next 
time I reinstall my Cubieboard.

The three major components in there are the dom0 kernel, the base installation 
filesystem and the Xen/ARM hypervisor.  Your patch touches the "difficult" part 
with a kernel modification, so we just need to decide if it's a 
Cubieboard-specific fork or not.

Anil
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