Configure RAM size on iMX53 board

[Jose Luis Zabalza]

There is no form of detection. UBoot (a very old version) don't use
any CS1 address, except with the memtest command.
If memtest command is executed with 512MB version, UBoot hangs, as expected.
I set the mem kernel parameter using a environment variable and kernel
can reach CS1 memory.


2016-11-08 22:24 GMT+01:00 Sascha Hauer <s.hauer at pengutronix.de>:
> On Tue, Nov 08, 2016 at 09:51:36PM +0100, Jose Luis Zabalza wrote:
>> > So you have 512MiB on each chip select, so I assume that on the 512MiB
>> > board variants CS1 is not equipped.
>>
>> Yes, it is.
>>
>> >In that case you can in lowlevel.c
>> > test if you find SDRAM on CS1 and if not, disable the chip select
>> > completely in the SDRAM controller.
>>
>> OK. But how ? I enable CS0 and CS1 on DCD table. Is there any way to
>> tell barebox not to use CS1 ?
>>
>> > I am not sure how you can detect if there's SDRAM on CS1. I've seen
>> > situations in which the board just hangs if you access non existent RAM
>> > areas.
>>
>> I have tried it, but I have not be able to implement a code for
>> autodetect. If the code write or read a value on a position without
>> physical  chip, the microcontroller hangs. ????
>>
>> But it's not a problem. A solution is configure both CS and MMU. If
>> bootloader don't access to high positions, there is not problem. After
>> I set a environment variable with memory size and the mem kernel
>> parameter (or ATAG) does the rest.
>
> You said that both board variants work with the same U-Boot binary, how
> does it work there? Is there some detection mechanism or is it only some
> environment variable that you have to set manually?
>
> Sascha
>
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