[U-Boot] Memory size detection on P1011

[Felix Radensky <felix@embedded-sol.com>]

Hi York,

On 05/05/2011 04:29 PM, York Sun wrote:
> Felix,
>
> On Thu, 2011-05-05 at 16:17 +0300, Felix Radensky wrote:
>> Hi,
>>
>> I'm working on a custom board based on P1011.
>> There are 2 board flavours, with either 128MB or 256MB of soldered
>> DDR2 SDRAM. Having u-boot image per board works fine, but I'd like
>> to have a single image and use get_ram_size() to detect memory size
>> at runtime. So far I had no luck.
>>
>> The only significant difference between memory devices on these boards
>> is the number of banks: 4 banks on 128MB board and 8 banks on 256MB
>> board.
>>
>> The memory size detection logic is loosely based on the code in
>> boards/tqc/tqm85xx/sdram.c, but I use fsl_ddr_set_memctl_regs()
>> to configure DDR controller registers and enable the controller.
>> The sequence is:
>>
>> 1. Configure TLBs for 2GB DDR
>> 2. Configure LAWs for 2GB DDR
>> 3. Configure DDR controller registers and enable DDR controller,
>>       CS0_BNDS is set to 256MB.
>> 4. Iterate over possible memory sizes starting from the largest.
>>       Each iteration configures CS0_CONFIG (sets number of banks, rows
>> and columns)
>>       and runs get_ram_size()
>>
>> What I observe on 128MB board, is that only 32KB of RAM is detected in
>> both
>> first and second iteration. So it seems that setting number of banks
>> to 8 on
>> 4-bank devices is fatal, and cannot be changed even if CS0_CONFIG is
>> modified.
>>
>> I've tried to rerun DDR controller initialization sequence with new
>> CS0_CONFIG
>> value, but that just hangs the board. I've also tried to disable DDR
>> controller via
>> RORDEVDISR register and then enable it and reconfigure DDR. That also
>> leads
>> to hang.
>>
>> I hope Freescale gurus on the list can help me to find a solution.
>>
>> Thanks in advance.
>>
> I don't think get_ram_size works for your case. If you want to test the
> DDR to find the correct size, you have to initialize the DDR first. But
> you cannot do this correctly without knowing the number of banks. You
> may be able to blindly set the bank number and test the DDR to catch the
> error if there is any, but you have to run this code somewhere else, for
> example, in the flash (before relocation).
>
> There might be another way. Do you have any board ID to distinguish
> these two kinds?
>
> York
>
>

Thanks a lot for a prompt reply, I appreciate it very much.

I suspected this might be the case. The tqm boards I've
used as a reference all have 4-bank memory devices, so
that's why it get_ram_size() works for them.

We'll have to keep board ID on EEPROM to distinguish
between boards with different RAM sizes.

Thanks a lot for your help.

Felix.