[U-Boot] [PATCH v2 04/11] fdt: Add device tree memory bindings

[Simon Glass]

Hi Tom,

On 20 November 2014 at 10:42, Simon Glass <sjg at chromium.org> wrote:
> Hi Tom,
>
> On 20 November 2014 14:37, Tom Rini <trini at ti.com> wrote:
>> On Wed, Nov 12, 2014 at 03:14:35PM -0700, Simon Glass wrote:
>>
>> [snip, and sorry for the late reply]
>>> What I am talking about here is the memory for U-Boot - i.e. how does
>>> U-Boot know how much memory is available. The scheme here is that you
>>> can have a board ID which controls this, with the U-Boot device tree
>>> allowing the options to be specified (i.e. the mapping from board ID
>>> to SDRAM banks)
>>
>> OK.  So what I'm getting at is how is this different from other boards
>> where we say "Oh, this is $FOO, it has $X LPDRR2 RAM" and "Oh, this is
>> $BAR, it has $Y DDR3 RAM" ?  The only thing I'm able to think of is that
>> we cannot call get_ram_size() to see the _size_ of the RAM after doing
>> $whatever to see what board we're on and doing the right configuration
>> for the DDR controller or whatever.
>
> Yes the memory type can go in the FDT too (and does for snow and pit).
>
> That's right, we can call get_ram_size() but only within the known
> boundaries. If we try to probe a 2GB machine as if it has 4GB of RAM
> it will hang. So we have to *know*.

I have left this one out so far, but would like to apply it. With this
I can support Pit and Pi (and with a bit more work Snow and Spring)
with the same U-Boot board, dealing with the memory differences
between the boards.

Regards,
Simon