Boards only supporting 16bit ram writes
Martin Fuzzey
mfuzzey at parkeon.com
Thu Sep 12 10:24:25 EDT 2013
Hello,
I have a board with a FRAM device which I am trying to get to work with
mtd-ram, on a DT based system (i.MX53) using physmap-of.
The chip is connected to a 16 bit data bus, however the signals that are
supposed to indicate which of the upper and lower bytes
are not connected to the processor but forced so as to use both bytes.
This means that all write operations must be done 16bits at a time (read
operations are fine since the processor handles that).
Looking at the mtd code it seems possible to support this using specific
mapping functions.
However it's likely to be a little complicated / ugly, especially for
partial unaligned writes which will have to do a read, mask, write.
So my questions:
* Is there currently any way of doing this?
* Would a patch implementing it be acceptable for mainline or would it
be a case of "go fix your hardware"?
Also while looking at this I noticed that
Documentation/devicetree/bindings/mtd/mtd-physmap.txt refers to a property
"device-width" which is used in a number of files in
arch/powerpc/boot/dts but I can't find any code that actually implements it.
Regards,
Martin
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