Grant Likely wrote:
> On Wed, Mar 25, 2009 at 2:48 PM, Wolfgang Grandegger <w...@grandegger.com>
> wrote:
>> Grant Likely wrote:
>>> For the chip offset, it's not clear what the meaning is. First, does
>>> the UPM controller support access of multiple chips simultaneously?
>> The offset drives the corresponding address lines, which are used to
>> select the chip. That's how it's done on the TQM8548 board. In
>> principle, the chips could also be selected through dedicated GPIO pins.
>> Well, I'm not a hardware guy.
>
> Heh. I mean elaborate in the binding documentation. :-)
>
>>> If so, then can you elaborate in the description on how board design
>>> translates to a chip-offset value. If it cannot, then it might be
>>> better to have multiple tuples in the 'reg' property for each discrete
>>> chip. Multiple reg tuples would also remove the need for the
>>> num-chips property.
>> The node still describes one device mapping all relevant control
>> registers. How about using fsl,upm-chip-offsets = <0x200 0x400>. It
>> would be more generic and makes num-chips obsolete as well. And the
>> property would be reserved for that way of implementing the chip select
>> in hardware.
>
> It really sounds like this binding is describing multiple NAND chips
> mapped to different base addresses (and looking at the fsm_upm.c
> driver appears to confirm it). So, does this work? reg = <3 0x200 4
> 3 0x400 4>;
The chip-offset, and not the address, needs to be added to the MAR
register as well before running the pattern:
mar = cmd << (32 - fun->upm.width);
if (fun->chip_offset && fun->chip_number > 0)
mar |= fun->chip_number * fun->chip_offset;
fsl_upm_run_pattern(&fun->upm, chip->IO_ADDR_R, mar);
> It is true that other methods could be used for implementing the chip
> select, but that is *not* what the proposed binding describes. This
> proposed binding describes NAND chips selected by address lines
> (particular addresses), and in this case I think using reg is the
> natural description.
OK, the chips are selected by accessing a defined address range. Will
prepare a patch using the reg property.
Wolfgang.
> g.
>
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