Re: [Qemu-arm] [Qemu-devel] [PATCH 3/3] hw/arm/virt-acpi-build: Add second UART to ACPI tables

[Laszlo Ersek]

On 12/12/17 12:11, Peter Maydell wrote:
> On 12 December 2017 at 11:06, Laszlo Ersek <address@hidden> wrote:
>> BTW, has anyone tested this with the ArmVirtQemu firmware? As far as I
>> can see from the firmware code, the firmware will use the PL011 whose
>> description comes first in the DTB (and ignore the other PL011), in an
>> fdt_next_node() traversal. Is that OK for the intended use case?
>> (Perhaps I should have asked this under the second patch, which updates
>> the DTB generator.)
> 
> I haven't tested, since I don't have a working setup for that to hand.
> (Do you have instructions somewhere for getting it working?)

The Wiki page I most frequently refer to (for a libvirt-less description
anyway) is Ard's:

  https://wiki.linaro.org/LEG/UEFIforQEMU

There's also:

  https://www.kraxel.org/repos/
  https://fedoraproject.org/wiki/Architectures/AArch64/Install_with_QEMU

> The behaviour we would want would be for the firmware to keep using
> the PL011 at 0x09000000.

With these QEMU patches, I reckon that's going to happen, yes.

> (In an ideal world the firmware would
> prefer the UART marked in the 'stdout-path' in the DTB /chosen node,
> as the kernel does, I guess.)

Hmmm, I recall that we used to have some code related to the /chosen
node... We have a helper function for locating that
(GetOrInsertChosenNode), but we no longer use it, it seems? The last
(only?) use was apparently removed in:

https://github.com/tianocore/edk2/commit/29589acf1010

I'll let Ard comment too.

Thanks
Laszlo