[U-Boot] [PATCH v3 8/9] tegra: i2c: Enable new CONFIG_SYS_I2C framework

[Heiko Schocher <hs@denx.de>]

Hello Albert,

Am 01.08.2013 08:53, schrieb Albert ARIBAUD:
> Hi Heiko,
>
> On Thu, 01 Aug 2013 08:02:42 +0200, Heiko Schocher<hs@denx.de>  wrote:
>
>>> I suppose you could. It seems conceptually /far/ simpler to just scan
>>> the DT once up-front rather than having to defer all this stuff until
>>
>> on the other hand we ring for every ms boot time ... and here we want
>> to scan a complete dt with maybe a lot of nodes, we do not want to
>> use?
>
> Scanning all of DT seems to imply it has no strict or standard
> ordering. Could we mandate, suggest, of make it so that all entries in
> the DT needed at _f time are put first, and even maybe place an "end of
> _f" custom marker in DT to delimit them? (I assume that, for the sake of

I do not know, if this is possible, as I think the DT used in U-Boot
should be the same as used in linux ... or?

> Postel-ism, anything in DT which is not understandable is skipped, so
> other users of the DT than us would not even be annoyed by such a
> marker)
>
> This way, we'd avoid wasting time scanning most of the DT in this case.

Hmm.. why should we introduce such things, instead of scanning the
node only if we need it?

We have "only" the problem, that we could not write to data at this
moment ... but this problem should be solved in a seperate topic.
I2C is usable before relocation, the problem is in conjunction with
dt, that we can not save for example the base address of the controller,
which we get from the DT ... If I understand it correct!

So we need an option when using dt, that we have (small ram) in which
we can write some parameters parsed from dt ...

I think this problem have all subsystems used before relocation.
(for example: environment on a spi flash?)

As Wolfgang said:
"Agreed - actually we're entering an area hear that smells pretty
strong like device model reorganization :-)"

BTW: How is this problem solved with the device model approach?

> Note: I confess I don't even know at the moment how DT is structured, so
> I may have talked complete nonsense above. If so, please forgive me and
> point me to some DT 101 course for me to avoid shame (at least on this
> topic) in the future.

bye,
Heiko
-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany