Anton Vorontsov wrote: > On Thu, Mar 26, 2009 at 11:02:06AM -0600, Grant Likely wrote: > [] >>>> 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).
Yep. > 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. I fully agree. I'm going to provide a patch on monday. Wolfgang. _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev
