[PATCH] powerpc: Create "rom" (MTD) device prpmc2800
Sergei Shtylyov
sshtylyov at ru.mvista.com
Mon Jun 4 09:34:08 EDT 2007
Hello.
Segher Boessenkool wrote:
>>>>> This has nothing to do with a "chip level", it is plain and
>>>>> simply the most basic device tree stuff.
>>>> If it was as "plain and simple" as you say, there would be
>>>> nothing to argue about.
>>> There isn't as far as I am concerned; the purpose and
>>> meaning of the "compatible" property, as well as of any
>>> other standard OF properties, is clear.
>> Erm, concerning matching those with drivers it wasn't as clear that
>> those props aren't the same as driver names b/c of the follwing
>> passage in Generic Names:
> [huge snip]
> Please point out the exact passage you don't understand, and
> what you don't understand about it, if you want any help.
Ah, nevermind... It was too late in the Sunday evening. :-)
>>> Yes, the more complex (and sometimes insane) ways that
>>> flash chips are connected to systems can be really hard
>>> to describe properly. Which is why I don't even want
>>> to make a "binding" for it (yet). It seems easy enough
>> Neither do we. :-)
>>> to do this for single flash chips (possibly direct-mapped)
>>> though.
>> Erm, FSL boards seem to generally have dual 16-bit NOR flash chips
>> interleaved -- and that's seems quite a common case, not only in PPC
>> world.
> It's not all that common; I can see why it would be used on
> flash controllers that handle a 32-bit bus only.
OK, maybe it's just we, embedded guys, that comes to see only such cheapo
boards. :-)
>> Perhaps... those interleaved chips could really be merged
>> (abstracted) into a single one, with the bus width being a sum of two?
> Perhaps. It is a nasty situation, it'll take long hard
> thinking to come up with a reasonably good solution.
I hoped to get some hints from the linux-mtd list as well...
>>> Get the simple cases
>>> (that actually are used in real life) right, first.
>> We pursued this task exactly. Get it working, quick. :-)
> That is something *TOTALLY DIFFERENT* and quite a bad plan
> IMNSHO.
I haven't considered 2 inteleaved 16-bit CFI NOR flashes a complex case so
far, sorry. :-) And that's what I had on my board. Prior to my acquaintance
with the device trees, this was indeed a no-brainer. :-)
> Segher
WBR, Sergei
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