Re: [PATCH 02/16] arm: qemu: Explain how to extract the generate devicetree

[Simon Glass]

Hi François,

On Tue, 12 Oct 2021 at 19:20, François Ozog <francois.ozog@linaro.org> wrote:
>
>
>
> Le mer. 13 oct. 2021 à 03:02, Simon Glass <sjg@chromium.org> a écrit :
>>
>> QEMU currently generates a devicetree for use with U-Boot. Explain how to
>> obtain it.
>>
>> Signed-off-by: Simon Glass <sjg@chromium.org>
>> ---
>>
>>  doc/board/emulation/qemu-arm.rst | 12 ++++++++++++
>>  1 file changed, 12 insertions(+)
>>
>> diff --git a/doc/board/emulation/qemu-arm.rst 
>> b/doc/board/emulation/qemu-arm.rst
>> index 97b6ec64905..b458a398c69 100644
>> --- a/doc/board/emulation/qemu-arm.rst
>> +++ b/doc/board/emulation/qemu-arm.rst
>> @@ -91,3 +91,15 @@ The debug UART on the ARM virt board uses these settings::
>>      CONFIG_DEBUG_UART_PL010=y
>>      CONFIG_DEBUG_UART_BASE=0x9000000
>>      CONFIG_DEBUG_UART_CLOCK=0
>> +
>> +Obtaining the QEMU devicetree
>> +-----------------------------
>> +
>> +QEMU generates its own devicetree to pass to U-Boot and does this by 
>> default.
>> +You can use `-dtb u-boot.dtb` to force QEMU to use U-Boot's in-tree version.
>
> this is for either Qemu experts or u-boot for Qemu maintainers. Not for the 
> kernel développer as it is recipe for problems: could you add this warning ?

Yes I can do that...or would it be better to hide this in doc/develop
somewhere with a link here?

>>
>>
>> +
>> +To obtain the devicetree that qemu generates, add `-machine 
>> dumpdtb=dtb.dtb`,
>> +e.g.::
>> +
>> +    qemu-system-aarch64 -machine virt -nographic -cpu cortex-a57 \
>> +           -bios u-boot.bin -machine dumpdtb=dtb.dtb
>> --
>> 2.33.0.882.g93a45727a2-goog
>>

Regards,
Simon