[RFC] smsc911x device tree binding questions

[Steve.Glendinning at smsc.com]

> A question though(16-bit/32-bit controllers, e.g. 9118):
> 
> If the device is strapped to 16-bit host bus mode, a single read 32-bit 
would 
> reveal us if the bus converts the load 32-bit to two load 16-bit or
> not because the D[31:16] data bus lines are left in a high impedance 
state. 
> Right ?

Right.

> Maybe a pair of reads - same address -  is safer, the controller 
invalidate 
> the read (what does it mean in terms of bytes read ?) if it samples the 
same 
> address (load 32 not split in 16-bit loads) on consecutive reads.
> If the conversion is correct the smsc returns the BYTE_TEST value 
otherwise 
> we would notice the problem. 

If the device is strapped for 16-bit we must ALWAYS read or write in 
pairs.
Actually, one of the two reads is *supposed* to have A[1] set and one is 
supposed
to have it cleared to read the two halves.  The data sheet says that 
reading
the same 16-bit word twice gives invalid results but is not fatal.

> I can write the code in the DT port context, but I do not have any
> 16-bit strapped smsc lan controller at hand, so I cannot test it, but I 
can post
> the patch for review and testing on the list.

Quite a few device variants are 16-bit only (e.g. 9221), so there are 
plenty out
there.