When changing from one data interface setting to another, one has to
ensure a specific sequence which is described in the ONFI spec.

One of these constraints is that the CE line has go high after a reset
before a command can be sent with the new data interface setting, which
is not guaranteed by the current implementation.

Rework the nand_reset() function and all the call sites to make sure the
CE line is asserted and released when required.

Also make sure to actually apply the new data interface setting on the
first die.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Fixes: d8e725dd8311 ("mtd: nand: automate NAND timings selection")
Reviewed-by: Sascha Hauer <s.hauer@pengutronix.de>
Tested-by: Marc Gonzalez <marc_gonzalez@sigmadesigns.com>

Introduction of the MTD pairing scheme concept.

Provide a nand_cleanup() function to free all nand related resources
without unregistering the mtd device.
This should allow drivers to call mtd_device_unregister() and handle
its return value and still being able to cleanup all nand related
resources.

Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Daniel Walter <dwalter@sigma-star.at>
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>

The generic NAND DT bindings allows one to tweak the ECC strength and
step size to their need. It can be used to lower the ECC strength to
match a bootloader/firmware config, but might also be used to get a better
reliability.

In the latter case, the user might want to use the maximum ECC strength
without having to explicitly calculate the exact value (this value not
only depends on the OOB size, but also on the NAND controller, and can
be tricky to extract).

Add a generic 'nand-ecc-maximize' DT property and the associated
NAND_ECC_MAXIMIZE flag, to let ECC controller drivers select the best
ECC strength and step-size on their own.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Acked-by: Rob Herring <robh@kernel.org>

The NAND framework provides several helpers to query timing modes supported
by a NAND chip, but this implies that all NAND controller drivers have
to implement the same timings selection dance. Also currently NAND
devices can be resetted at arbitrary places which also resets the timing
for ONFI chips to timing mode 0.

Provide a common logic to select the best timings based on ONFI or
->onfi_timing_mode_default information. Hook this into nand_reset()
to make sure the new timing is applied each time during a reset.

NAND controller willing to support timings adjustment should just
implement the ->setup_data_interface() method.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

The nand layer will need ONFI mode 0 to use it as timing mode
before and right after reset.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>

onfi_init_data_interface() initializes a data interface with
values from a given ONFI mode.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>

Currently we have no data structure to fully describe a NAND timing.
We only have struct nand_sdr_timings for NAND timings in SDR mode,
but nothing for DDR mode and also no container to store both types
of timing.
This patch adds struct nand_data_interface which stores the timing
type and a union of different timings. This can be used to pass to
drivers in order to configure the timing.
Add kerneldoc for struct nand_sdr_timings while touching it anyway.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>

When NAND devices are resetted some initialization may have to be done,
like for example they have to be configured for the timing mode that
shall be used. To get a common place where this initialization can be
implemented create a nand_reset() function. This currently only issues
a NAND_CMD_RESET to the NAND device. The places issuing this command
manually are replaced with a call to nand_reset().

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>

'extern' is not necessary for function declarations. To prevent
people from adding the keyword to new declarations remove the
existing ones.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>