[U-Boot] CONFIG_MIPS_BOOT_CMDLINE_LEGACY usage ?

[Stefan Roese]

Hi Daniel,

On 15.08.2018 15:01, Daniel Schwierzeck wrote:
> On 15.08.2018 10:23, Stefan Roese wrote:
>> Hi Daniel,
>>
>> I'm wondering about the CONFIG_MIPS_BOOT_CMDLINE_LEGACY Kconfig
>> option in MIPS. Why is this one called "legacy" and what should
>> be used instead to pass the U-Boot bootargs to the Linux kernel?
>>
>> Thanks,
>> Stefan
> 
> This interface was initially added to U-Boot with MIPS support and is
> copied from the MIPS Yamon bootloader. Dependent on the platform and the
> used bootloader there are more different boot interfaces.
> 
> The modern way to boot a kernel on MIPS would be to add a DTB to the
> kernel FIT image and let U-Boot pass it over to the kernel
> (CONFIG_MIPS_BOOT_FDT). All bootargs would then be added automatically
> to the /chosen/bootargs node. This interface is conformant with the MIPS
> UHI boot protocol. The kernel supports this in a generic way. The PROM
> code of a platform only needs to evaluate the fw_passed_dtb variable for
> a DTB address. In your case the Ralink platform supports this.
> 
> But you still have the flexibility to use a DTB built-in or appended to
> the kernel and pass the bootargs in the traditional way. The kernel has
> various config options to select the source of bootargs.

I see. Thanks for the detailed answer. We'll move over to passing via
DT once this is ready in Linux. Until then, we will use this legacy
interface.

Thanks,
Stefan