[U-Boot] CONFIG_MIPS_BOOT_CMDLINE_LEGACY usage ?

[Daniel Schwierzeck]

On 15.08.2018 15:13, Stefan Roese wrote:
> 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.
> 

DT handover is already supported for Ralink/mMediatek platform, see [1]

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/mips/ralink/of.c#n78


-- 
- Daniel

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