On Thu, Mar 26, 2009 at 11:02:06AM -0600, Grant Likely wrote:
[]

quoted

quoted

Here is another thought.  The binding is describing that address lines
are used to activate CS lines.  Offset for chip access purposes is
derived from the address line, but it doesn't directly describe the
hardware.  The following may be a better description of the hardware.

fsl,upm-addr-line-cs = <9 10>;

The TQM8548 hardware has some logic connected to the two address lines
allowing to select up to 4 chips with two address lines:

 fsl,upm-addr-line-cs-offsets = <0x0 0x200 0x400 0x600>

Ah.  I see.  This is board specific then.  I think it is premature to
try and define a generic solution here because it depends on custom
board hardware and different boards could use very different logic.
The next board could end up doing something completely different.  I'd
rather start to see trends in multiple boards implementing the same
scheme before trying to craft a generic scheme.

In other words, this device is not register-level compatible with the
fsl,upm-nand device.  Give the node a new compatible value
(tqc,tqm8548-upm-nand) and add another entry to the of_fun_match table
for the new device.  Use the .data element in the match table to
supply an alternate fun_cmd_ctrl() function for this board (instead of
using a property value do decide which fun_cmd_ctrl() behaviour to
use).  New boards that *do* use the same addressing scheme can claim
compatibility with tqc,tqm8548-upm-nand.

I don't like this. :-/

UPM is an universal thing, so there are thousands of ways we can
connect NAND to the UPM. Of which only ~10 would be sane (others are
insane, and nobody would do this. If they do, _then_ we'll fall back
to <board>-upm-nand scheme for a particular board).

I don't see any problem with fsl,upm-addr-line-cs-offsets. It can
describe any scheme in "addr lines are cs" connection, it's a common
setup for multi-chip memory, we shouldn't treat it is as something
extraordinary.

-- 
Anton Vorontsov
email: cbouatmailru@gmail.com
irc://irc.freenode.net/bd2