[U-Boot] Passing bootargs to arm64 kernel

[U-Boot] Passing bootargs to arm64 kernel

[Youngmin Nam]

Hello.
I'm trying to find a way how to pass bootargs to arm64 kernel.

In arm32 kernel, we can pass bootargs with atag from u-boot to kernel. So,
we can overwrite kernel's bootargs with u-boot's bootargs.

But from arm64 kernel, the dtb is the only argument that should be passed
from bootloader which is mandatory.
you can find this contents in kernel
documentation.(Documentation/arm64/Booting.txt)

So,  is there any way how to set bootargs by u-boot?

Thanks.

[U-Boot] Passing bootargs to arm64 kernel

[Tom Rini]

On Wed, Aug 13, 2014 at 11:21:32AM +0900, Youngmin Nam wrote:

> Hello.
> I'm trying to find a way how to pass bootargs to arm64 kernel.
> 
> In arm32 kernel, we can pass bootargs with atag from u-boot to kernel. So,
> we can overwrite kernel's bootargs with u-boot's bootargs.
> 
> But from arm64 kernel, the dtb is the only argument that should be passed
> from bootloader which is mandatory.
> you can find this contents in kernel
> documentation.(Documentation/arm64/Booting.txt)
> 
> So,  is there any way how to set bootargs by u-boot?

Yes, within the device tree, like we do today.  There's a few issues we
have today, but I need to re-post the booti command support patches,
given what's coming in 3.17 in the kernel.

-- 
Tom
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[U-Boot] Passing bootargs to arm64 kernel

[Youngmin Nam]

Thank you for reply Tom,
Let me ask you some questions.

Can we set kernel's bootargs without re-compiling device tree on arm64
kernel by u-boot?

I mean, I want to set kernel's bootargs by u-boot without re-compiling
device tree.

Is it possible?
2014. 8. 13. ?? 7:39? "Tom Rini" <trini@ti.com>?? ??:

> On Wed, Aug 13, 2014 at 11:21:32AM +0900, Youngmin Nam wrote:
>
> > Hello.
> > I'm trying to find a way how to pass bootargs to arm64 kernel.
> >
> > In arm32 kernel, we can pass bootargs with atag from u-boot to kernel.
> So,
> > we can overwrite kernel's bootargs with u-boot's bootargs.
> >
> > But from arm64 kernel, the dtb is the only argument that should be passed
> > from bootloader which is mandatory.
> > you can find this contents in kernel
> > documentation.(Documentation/arm64/Booting.txt)
> >
> > So,  is there any way how to set bootargs by u-boot?
>
> Yes, within the device tree, like we do today.  There's a few issues we
> have today, but I need to re-post the booti command support patches,
> given what's coming in 3.17 in the kernel.
>
> --
> Tom
>

[U-Boot] Passing bootargs to arm64 kernel

[Arnab Basu]

On 08/14/2014 08:04 AM, Youngmin Nam wrote:
> Thank you for reply Tom,
> Let me ask you some questions.
> 
> Can we set kernel's bootargs without re-compiling device tree on arm64
> kernel by u-boot?
> 
> I mean, I want to set kernel's bootargs by u-boot without re-compiling
> device tree.
> 
> Is it possible?

This is done anyway, whatever is defined in CONFIG_BOOTARGS will be
stored in the U-Boot environment variable bootargs and passed as
bootargs to the kernel via the "chosen" node.

See fdt_chosen in common/fdt-support.c.

So if you want the change the bootargs passed to the kernel, just do

> set bootargs '<whatever you want in bootargs>'

at the u-boot prompt and the boot the kernel.

Thanks
Arnab

> 2014. 8. 13. ?? 7:39? "Tom Rini" <trini@ti.com>?? ??:
> 
>> On Wed, Aug 13, 2014 at 11:21:32AM +0900, Youngmin Nam wrote:
>>
>>> Hello.
>>> I'm trying to find a way how to pass bootargs to arm64 kernel.
>>>
>>> In arm32 kernel, we can pass bootargs with atag from u-boot to kernel.
>> So,
>>> we can overwrite kernel's bootargs with u-boot's bootargs.
>>>
>>> But from arm64 kernel, the dtb is the only argument that should be passed
>>> from bootloader which is mandatory.
>>> you can find this contents in kernel
>>> documentation.(Documentation/arm64/Booting.txt)
>>>
>>> So,  is there any way how to set bootargs by u-boot?
>>
>> Yes, within the device tree, like we do today.  There's a few issues we
>> have today, but I need to re-post the booti command support patches,
>> given what's coming in 3.17 in the kernel.
>>
>> --
>> Tom
>>