Re: [Qemu-devel] [PATCH v12 4/4] arm: SoC model for Calxeda Highbank

From:

John Williams

Subject:

Date:

Fri, 20 Jan 2012 09:41:10 +1000

On Fri, Jan 20, 2012 at 9:17 AM, Rob Herring <address@hidden> wrote:

On 01/19/2012 03:44 PM, Peter Maydell wrote:
> On 19 January 2012 21:31, Mark Langsdorf <address@hidden> wrote:
>> + highbank_binfo.board_id = 0xEC10100f; /* provided by deviceTree */
>
> Where does this number come from? It's not in
> http://www.arm.linux.org.uk/developer/machines/
>
> Is 3027 (==0xbd3) you?
> http://www.arm.linux.org.uk/developer/machines/list.php?id=3027
>

Much of the data there is wrong as none of it is used. 0 or -1 is the
right value as those are obviously meaningless. A highbank kernel will
never be booted without devicetree and in that case this number is
irrelevant. This is the legacy boot interface and qemu really needs to
learn to boot with a separate dtb.

We partially addressed this issue in our rejected device tree machine model patch series from last year. We added two new DTB-related arguments to the qemu cmdline:

--kernel-dtb which is the DTB that gets passed through to the kernel, and

--hw-dtb which is the DTB describing the actual hardware (we were making QDEV system models by scanning and parsing the device tree)

If only a HW DTB is provided, then that same DTB is used for the kernel. There are situations when you might want them to be different.

Rgds,

John