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

[Simon Glass]

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*.

Regards,
Simon