[RFC 0/1] use lmb to calculate ram left for the kernel

[Tomas Alvarez Vanoli]

>I am confused here. You mention above that the address of the rootfs is determined based on its size. So you do know the memory that would be needed for the rootfs? Also, how does calculating the amount of RAM left over for the kernel help. I mean, what if the kernel is bigger than the amount of >left over memory? Can that not happen if you don't know the amount of memory that would be needed for the kernel as you mention above.

Sorry, maybe I misused the term "kernel memory". I am referring to the amount of physical ram available for the kernel to use:

From the kernel parameter docs:

```
        mem=nn[KMG]     [KNL,BOOT] Force usage of a specific amount of memory
                        Amount of memory to be used when the kernel is not able
                        to see the whole system memory or for test.
                        [X86] Work as limiting max address. Use together
                        with memmap= to avoid physical address space collisions.
                        Without memmap= PCI devices could be placed at addresses
                        belonging to unused RAM.
```

We know the memory that is needed based for the rootfs "in runtime", it's not something we can compile into u-boot (if you add a new binary to the rootfs then it's bigger).
We don't want the kernel to be touching this piece of memory that emulates the mtd partition.

I hope this clears up the usecase.

Tomas