[U-Boot] [PATCH 6/6] board: bcm28155_ap: Add board files

[Tom Rini]

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On 01/31/2014 12:05 PM, Tim Kryger wrote:
> On Fri, Jan 31, 2014 at 6:17 AM, Tom Rini <trini at ti.com> wrote:
>> On 01/30/2014 06:05 PM, Darwin Rambo wrote:
>>> We tried using this on our reference board and it hangs accessing
>>> memory regions that are not populated. Our memory controller
>>> doesn't appear to properly support accessing regions that are not
>>> backed by physical sdram. So I think it's best to keep this code as
>>> is and consider this approach for future designs.
>>
>> Wait, what did you do?  get_ram_size(base, max) must work and return
>> CONFIG_SYS_SDRAM_SIZE, or you haven't properly configured your
>> controller (as get_ram_size just pokes parts of the specified range).
> 
> Tom,
> 
> In my experience, there are three general ways memory controllers
> behave when an access is made to an address that could be backed by
> RAM but isn't on a particular board.
> 
> 1. All reads return a fixed pattern and writes are ignored
> 2. A bus error is triggered that the CPU sees as a data abort
> 3. No response to the transaction so the bus and CPU lock up
> 
> I believe the Broadcom memory controller can only behave in the third,
> least desirable way.

That's fine.  You should still use get_ram_size(base,
CONFIG_SYS_SDRAM_SIZE) like other platforms use as this go above the max
size it's given.  If this hangs, you have a problem with your
configuration of the memory controller.  Make sense?

- -- 
Tom
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