Re: Design doc of adding ACPI support for arm64 on Xen - version 2

[Ian Campbell <ian.campbell@citrix.com>]

On Wed, 2015-08-12 at 13:20 +0100, Julien Grall wrote:
> On 12/08/15 11:36, Andrew Turner wrote:
> > Would it be possible to add a stdout property and node for the hvc0
> > device? It would help FreeBSD as we use this to find the kernel
> > console. We check for the stdout-path, linux,stdout-path, stdout,
> > stdin-path, and stdin properties, in that order, with the first
> > property selected as the console. If none are found we fall back to
> > searching for a serial0 device. You can see how we find the device at
> > [1].
> 
> the stdout-path property is used by Xen in order to get the UART. The
> property will be removed from the device tree passed to DOM0.
> 
> The Xen console is not UART a driver so having a property with "hvc"
> wouldn't help here.

If it were helpful we could of course create some sort of dummy node or do
something else to make it work. But it really shouldn't be necessary
because...

> Although, when running on Xen, FreeBSD is creating a Xen console by
> default with the higher priority. It will be grabbed by FreeBSD as the
> default one.

... Linux should be doing the same. The problem is that the existing code
to call add_preferred_console doesn't happen early enough on ARM

Someone (you? Ard? Stefano?) has a patch to move Xen detection in Linux
earlier ages ago, but I think it failed to actually get in.

Ian.