[U-Boot] [PATCH 3/8] boottime: Add core boottime measurement support

[Lee Jones]

> > Boottime is a tool which can be used for full system booting time
> > measurement. Bootloader boot time is passed to the kernel component
> > though ATAGS. The kernel-side driver then uses this information to
> > provide full system boot time diagnostics though debugfs.
> 
> Aren't we converting more and more systems to use the device treee to
> pass information to the kenrel, with the result that ATAGS are kind
> of becoming extinct?

Yes, I intend to extend this functionality into Device Tree.
That way it will be architecture and OS independent.

> And forcing something upon a mechanism that was designed for a
> completely different purpose, where you see right from the first
> glance that it does  not math easily?

Not entirely sure what you mean here. This mechanism works
perfectly with ATAGs.

> This makes no sense to me.  Why don't you use standard mechanisms, like
> a shared log buffer, and simply create time-stamped entries into the
> kernel boot log?
>
> The advantages should be obvious: we will need no extra kernel
> modification, we do not depend on ATAGS, and we are automatically
> architecture-independent.

Wouldn't this clog up the kernel's log buffer? I'm sure no
user wants to see reams of otherwise useless logging scrawled
throughout their bootlog. We'd also have a write a text parser
to obtain the information for processing. It would be easier
to either pass in a struct, as we do with the ATAG mechanism,
or though Device Tree as previously discussed.

-- 
Lee Jones
Linaro ST-Ericsson Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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