[U-Boot] i.MX6 Solo and Dual Lite

[Eric Nelson]

Thanks for the feedback Stefano.

On 01/18/2013 06:55 AM, Stefano Babic wrote:
> On 16/01/2013 23:33, Eric Nelson wrote:
>> Hi all,
>>
>> <snip>
>>
>> Troy and I also had some discussion surrounding **how** the preprocessor
>> was used to define the differences between processors:
>>      http://lists.denx.de/pipermail/u-boot/2012-October/136751.html
>>
>> In a nutshell, the current patch set uses a set of preprocessor macros
>> to configure things for each. For example, this macro call in the file
>> mx6q_4x_mt41j128.cfg will write either 0x48254A36 (Quad or Dual)
>> or 0x3F3F3035 (Dual-Lite/Solo) to register MMDC_P1_MPWRDLCTL:
>>
>>      WRITE_ENTRY2(MMDC_P1_MPWRDLCTL, 0x48254A36, 0x3F3F3035)
>
> I read the patch and your comment on ML and agree with your comment. It
> seems to me that it is very tricky to add this macro to make possible to
> have a single imximage.cfg file. And, as you remark, this will work now
> with these set on boards, but things can be different with new SOC version.
>
Or even a different memory configuration. For example, this line in the
updated mx6q_4x_mt41j128.cfg file sets a value of 0x831A0000 to the
MMDC_MDCTL register for Quad/Dual or Dual-Lite devices, but a value
of 0x83190000 on Solo-Lite.

In English, this sets up a 64-bit memory bus except on Solo-Lite.
Since designs like ours do allow the use of a 32-bit bus on a
Quad Core machine, trying to represent all of the choices in
a single file doesn't scale.

WRITE_ENTRY3(MMDC_P0 + MMDC_MDCTL, 0x831A0000, 0x831A0000, 0x83190000)

> The concept here is that the processors use a different internal base
> address, and depending on this address, the macro does its work, writing
> on the selected address. But again, IMHO it is tricky, and it is
> strictly bound to i.MX6 when imximage is thought for all i.MX processors.
>
> Let's say, instead of it, I prefer the solution using the preprocessor
> or as you suggest, using different .cfg files for the memory configurations.
>

Yep. We'll proceed with the separate file approach.

>>
>> Nobody else seemed to comment on this, and it seems pretty critical.
>>
>> Can we get some feedback before we prepare V2/V3 patches?
>>
>> Our expectation is that we'll submit patches for each of the
>> following configurations of Nitrogen6X:
>>
>>      nitrogen6q        - Dual/Quad 1GB
>>      nitrogen6q2g    - Dual/Quad 2GB
>>      nitrogen6solo    - Solo 512MB
>>      nitrogen6duallite    - Dual Lite 512MB
>>      nitrogen6solo1G    - Solo 1GB
>>      nitrogen6duallite1G    - Dual Lite 1GB
>>
>> Our hope is that we can do this with essentially one code
>> base but a separate .cfg file or #ifdefs for each.
>
> I agree on this, but then do we still need WRITE_ENTRY2() ? I miss why
> we need if you use separate .cfg files.
>

No. We don't.

>>
>> A single include/config/nitrogen6x.h with #ifdefs should
>> allow us to exclude those features (e.g. SATA) on the
>> Solo and Dual-Lite.
>
> Right, I think it is a good solution.
>

Thanks again. I think we have a plan.

Regards,


Eric