Some of the GPMC timings parameters are currently missing from the GPMC
device-tree binding. Add these parameters to the binding documentation
as well as code to read them. Also add either "-ps" or "-ns" suffix to
the GPMC timing properties to indicate whether the timing is in
picoseconds or nanoseconds.

The existing code in gpmc_read_timings_dt() is checking the value of
of_property_read_u32() and only is successful storing the value read
in the gpmc_timings structure. Checking the return value in this case
is not necessary and we can simply read the value, if present, and
store directly in the gpmc_timings structure. Therefore, simplify the
code by removing these checks.

The comment in the gpmc_read_timings_dt() function, "only for OMAP3430"
is also incorrect as it is applicable to all OMAP3+ devices. So correct
this too.
Signed-off-by: NJon Hunter <jon-hunter@ti.com>
Tested-by: NEzequiel Garcia <ezequiel.garcia@free-electrons.com>

Adds a function to read the various GPMC chip-select settings from
device-tree and store them in the gpmc_settings structure.

Update the GPMC device-tree binding documentation to describe these
options.
Signed-off-by: NJon Hunter <jon-hunter@ti.com>
Tested-by: NEzequiel Garcia <ezequiel.garcia@free-electrons.com>

This patch adds basic DT bindings for OMAP GPMC.

The actual peripherals are instantiated from child nodes within the GPMC
node, and the only type of device that is currently supported is NAND.

Code was added to parse the generic GPMC timing parameters and some
documentation with examples on how to use them.

Successfully tested on an AM33xx board.
Signed-off-by: NDaniel Mack <zonque@gmail.com>
Acked-by: NGrant Likely <grant.likely@secretlab.ca>
[tony@atomide.com: updated to apply]
Signed-off-by: NTony Lindgren <tony@atomide.com>