[U-Boot] DDR training code for Armada 38x

[Chris Packham]

On Wed, Sep 20, 2017 at 5:31 PM, Stefan Roese <sr at denx.de> wrote:
> Hi Chris,
>
> On 19.09.2017 20:58, Chris Packham wrote:
>>
>> When you did the port from Marvell's source did you script any of the
>> tidy-up that you did along the way?
>
>
> Not really. At least not in a reproducible way. I spent long
> hours running Lindent, recursive-replace tools and especially
> manual code inspection and re-formatting on this huge code.
> Still the outcome is far from perfect, but hopefully better
> that the original version.
>
>> I'm running up a new board and with the upstream u-boot DDR training
>> occasionally fails. But with the Marvell bootloader it doesn't fail.
>> The initial port was done from TIP-1.29 but Marvell are now up to
>> TIP-1.55 so there is probably some difference that results in my board
>> working.
>>
>> One difference I've spotted so far is that Marvell enable 2T timing
>> mode for all Armada 38x boards (the comment says "resolve low freq
>> instability"). But doing that doesn't magically make my board work.
>
>
> Did you compare all DDR register values (the "good" ones and the "bad"
> ones) and only the the 2T timing is different?
>

There are more differences. 2T was the one that stuckout. As you know
working backwards from register values to where the code sets them can
be tricky with this code.

>> I'm thinking I need to compare TIP-1.29 with TIP-1.55 to look for
>> other differences but obviously that's going to be hard given the
>> style changes.
>
>
> Has the style changed in between the Marvell versions as well? I
> have not looked into this code for quite some time.
>

What I meant was u-boot has 1.29 and I have 1.55 from Marvell. The
oldest Marvell version I have is 1.34 which helped me find the 2T
thing. I'm wondering what differences exist between 1.29 and 1.34.
1.55 also has support for some newer integrated switch+CPU chips so it
is a little hard to separate those bits from the A38X code.

>> If you have any scripts (or even just a record of the
>> regexes) that you used would you be able to share them?
>
>
> Please find some scripts attached, I've located that I have used while
> doing this porting.

Thanks. That's a start at least.