spi: Unify error codes by replacing -ENOTSUPP with -EOPNOTSUPP

This commit updates the SPI subsystem, particularly affecting "SPI MEM"
drivers and core parts, by replacing the -ENOTSUPP error code with
-EOPNOTSUPP.

The key motivations for this change are as follows:
1. The spi-nor driver currently uses EOPNOTSUPP, whereas calls to spi-mem
might return ENOTSUPP. This update aims to unify the error reporting
within the SPI subsystem for clarity and consistency.

2. The use of ENOTSUPP has been flagged by checkpatch as inappropriate,
mainly being reserved for NFS-related errors. To align with kernel coding
standards and recommendations, this change is being made.

3. By using EOPNOTSUPP, we provide more specific context to the error,
indicating that a particular operation is not supported. This helps
differentiate from the more generic ENOTSUPP error, allowing drivers to
better handle and respond to different error scenarios.

Risks and Considerations:
While this change is primarily intended as a code cleanup and error code
unification, there is a minor risk of breaking user-space applications
that rely on specific return codes for unsupported operations. However,
this risk is considered low, as such use-cases are unlikely to be common
or critical. Nevertheless, developers and users should be aware of this
change, especially if they have scripts or tools that specifically handle
SPI error codes.

This commit does not introduce any functional changes to the SPI subsystem
or the affected drivers.

Signed-off-by: "Chia-Lin Kao (AceLan)" <acelan.kao@canonical.com>
Acked-by: Tudor Ambarus <tudor.ambarus@linaro.org>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Acked-by: Miquel Raynal <miquel.raynal@bootlin.com>
Acked-by: Michael Walle <michael@walle.cc>
Link: https://lore.kernel.org/r/20231129064311.272422-1-acelan.kao@canonical.com
Signed-off-by: Mark Brown <broonie@kernel.org>

spi: atmel-quadspi: Convert to platform remove callback returning void

The .remove() callback for a platform driver returns an int which makes
many driver authors wrongly assume it's possible to do error handling by
returning an error code. However the value returned is (mostly) ignored
and this typically results in resource leaks. To improve here there is a
quest to make the remove callback return void. In the first step of this
quest all drivers are converted to .remove_new() which already returns
void.

Trivially convert this driver from always returning zero in the remove
callback to the void returning variant.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reviewed-by: Tudor Ambarus <tudor.ambarus@linaro.org>
Link: https://lore.kernel.org/r/20230317084232.142257-4-u.kleine-koenig@pengutronix.de
Signed-off-by: Mark Brown <broonie@kernel.org>

spi: atmel-quadspi: Free resources even if runtime resume failed in .remove()

An early error exit in atmel_qspi_remove() doesn't prevent the device
unbind. So this results in an spi controller with an unbound parent
and unmapped register space (because devm_ioremap_resource() is undone).
So using the remaining spi controller probably results in an oops.

Instead unregister the controller unconditionally and only skip hardware
access and clk disable.

Also add a warning about resume failing and return zero unconditionally.
The latter has the only effect to suppress a less helpful error message by
the spi core.

Fixes: 4a2f83b7f780 ("spi: atmel-quadspi: add runtime pm support")
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reviewed-by: Tudor Ambarus <tudor.ambarus@linaro.org>
Link: https://lore.kernel.org/r/20230317084232.142257-3-u.kleine-koenig@pengutronix.de
Signed-off-by: Mark Brown <broonie@kernel.org>

spi: atmel-quadspi: Don't leak clk enable count in pm resume

The pm resume call is supposed to enable two clocks. If the second enable
fails the callback reports failure but doesn't undo the first enable.

So call clk_disable() for the first clock when clk_enable() for the second
one fails.

Fixes: 4a2f83b7f780 ("spi: atmel-quadspi: add runtime pm support")
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reviewed-by: Tudor Ambarus <tudor.ambarus@linaro.org>
Link: https://lore.kernel.org/r/20230317084232.142257-2-u.kleine-koenig@pengutronix.de
Signed-off-by: Mark Brown <broonie@kernel.org>

spi: atmel-quadspi: switch to use modern name

Change legacy name master to modern name host or controller.

No functional changed.

Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Link: https://lore.kernel.org/r/20230110131805.2827248-4-yangyingliang@huawei.com
Signed-off-by: Mark Brown <broonie@kernel.org>

spi: atmel-quadspi: Add support for configuring CS timing

The at91 QSPI IP uses a default value of half of the period of the QSPI
clock period for the cs-setup time, which is not always enough, an example
being the sst26vf064b SPI NOR flash which requires a minimum cs-setup time
of 5 ns. It was observed that none of the at91 SoCs can fulfill the
minimum CS setup time for the aforementioned flash, as they operate at
high frequencies and half a period does not suffice for the required CS
setup time. Add support for configuring the CS timing in the controller.

Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Link: https://lore.kernel.org/r/20221117105249.115649-5-tudor.ambarus@microchip.com
Signed-off-by: Mark Brown <broonie@kernel.org>

spi: atmel-quadspi: align condition to parenthesis

Align condition to parenthesis.

Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Link: https://lore.kernel.org/r/20220609084246.1795419-4-claudiu.beznea@microchip.com
Signed-off-by: Mark Brown <broonie@kernel.org>

spi: atmel-quadspi: use pm_ptr()

Use pm_ptr() for atmel_quadspi_pm_ops.

Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Link: https://lore.kernel.org/r/20220609084246.1795419-3-claudiu.beznea@microchip.com
Signed-off-by: Mark Brown <broonie@kernel.org>

spi: atmel-quadspi: add runtime pm support

Add runtime PM support for atmel-quadspi which will disable/enable
QSPI clocks on proper runtime_suspend/runtime_resume ops.

Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Link: https://lore.kernel.org/r/20220609084246.1795419-2-claudiu.beznea@microchip.com
Signed-off-by: Mark Brown <broonie@kernel.org>

spi: atmel-quadspi: Remove duplicated DTR checks

Remove the DTR checks as they are already handled in
spi_mem_default_supports_op(). This code removal was intentionally not done
in the previous patch that introduced the use of the
spi_mem_default_supports_op() core helper and fixed the buswidth adjustment
between SPIMEM and the SPI controller, so that the fix can be easily
backported to stable kernels.

Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Link: https://lore.kernel.org/r/20220406133604.455356-2-tudor.ambarus@microchip.com
Signed-off-by: Mark Brown <broonie@kernel.org>

spi: atmel-quadspi: Fix the buswidth adjustment between spi-mem and controller

Use the spi_mem_default_supports_op() core helper in order to take into
account the buswidth specified by the user in device tree.

Cc: <stable@vger.kernel.org>
Fixes: 0e6aae08e9ae ("spi: Add QuadSPI driver for Atmel SAMA5D2")
Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Link: https://lore.kernel.org/r/20220406133604.455356-1-tudor.ambarus@microchip.com
Signed-off-by: Mark Brown <broonie@kernel.org>

spi: Fixed division by zero warning

The reason for dividing by zero is because the dummy bus width is zero,
but if the dummy n bytes is zero, it indicates that there is no data transfer,
so there is no need for calculation.

Fixes: 7512eaf54190 ("spi: cadence-quadspi: Fix dummy cycle calculation when buswidth > 1")
Signed-off-by: Yoshitaka Ikeda <ikeda@nskint.co.jp>
Acked-by: Pratyush Yadav <p.yadav@ti.com>
Link: https://lore.kernel.org/r/OSZPR01MB70049C8F56ED8902852DF97B8BD49@OSZPR01MB7004.jpnprd01.prod.outlook.com
Signed-off-by: Mark Brown <broonie@kernel.org>

spi: atmel-quadspi: Disable the QSPI IP at suspend()

It is safer to disable the QSPI IP at suspend, in order to avoid
possible impact of glitches on the internal FSMs. This is a theoretical
fix, there were no problems seen as of now. Tested on sama5d2 and
sam9x60 versions of the IP.

Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Link: https://lore.kernel.org/r/20210210135428.204134-1-tudor.ambarus@microchip.com
Signed-off-by: Mark Brown <broonie@kernel.org>

spi: atmel-quadspi: Fix use-after-free on unbind

atmel_qspi_remove() accesses the driver's private data after calling
spi_unregister_controller() even though that function releases the last
reference on the spi_controller and thereby frees the private data.

Fix by switching over to the new devm_spi_alloc_master() helper which
keeps the private data accessible until the driver has unbound.

Fixes: 2d30ac5ed633 ("mtd: spi-nor: atmel-quadspi: Use spi-mem interface for atmel-quadspi driver")
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Cc: <stable@vger.kernel.org> # v5.0+: 5e844cc37a5c: spi: Introduce device-managed SPI controller allocation
Cc: <stable@vger.kernel.org> # v5.0+
Cc: Piotr Bugalski <bugalski.piotr@gmail.com>
Link: https://lore.kernel.org/r/4b05c65cf6f1ea3251484fe9a00b4c65478a1ae3.1607286887.git.lukas@wunner.de
Signed-off-by: Mark Brown <broonie@kernel.org>

spi: atmel-quadspi: Move common code outside of if else

QSPI_IFR is set as the last QSPI Instruction Frame register
regardless of the sama5d2 or sam9x60 version of the IP. Move
the writing of QSPI_IFR outside of the IP specific code.

Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Link: https://lore.kernel.org/r/20201207135959.154124-5-tudor.ambarus@microchip.com
Signed-off-by: Mark Brown <broonie@kernel.org>

spi: atmel-quadspi: Write QSPI_IAR only when needed

The address must be written in QSPI_IAR only when we have
a instruction frame with address but no data.

Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Link: https://lore.kernel.org/r/20201207135959.154124-4-tudor.ambarus@microchip.com
Signed-off-by: Mark Brown <broonie@kernel.org>

spi: atmel-quadspi: Drop superfluous set of QSPI_IFR_APBTFRTYP_READ

That bit describes the APB transfer type. We are writing
serial memory registers via AHB acesses, that bit does not
make sense in the current context.

Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Link: https://lore.kernel.org/r/20201207135959.154124-3-tudor.ambarus@microchip.com
Signed-off-by: Mark Brown <broonie@kernel.org>

spi: atmel-quadspi: Fix AHB memory accesses

Following error was seen when mounting a 16MByte ubifs:
UBIFS error (ubi0:0 pid 1893): check_lpt_type.constprop.6: invalid type (15) in LPT node type

QSPI_IFR.TFRTYP was not set correctly. When data transfer is enabled
and one wants to access the serial memory through AHB in order to:
- read in the serial memory, but not a memory data, for example
a JEDEC-ID, QSPI_IFR.TFRTYP must be written to '0' (both sama5d2
and sam9x60).
- read in the serial memory, and particularly a memory data,
TFRTYP must be written to '1' (both sama5d2 and sam9x60).
- write in the serial memory, but not a memory data, for example
writing the configuration or the QSPI_SR, TFRTYP must be written
to '2' for sama5d2 and to '0' for sam9x60.
- write in the serial memory in particular to program a memory data,
TFRTYP must be written to '3' for sama5d2 and to '1' for sam9x60.

Fix the setting of the QSPI_IFR.TFRTYP field.

Fixes: 2d30ac5ed633 ("mtd: spi-nor: atmel-quadspi: Use spi-mem interface for atmel-quadspi driver")
Cc: <stable@vger.kernel.org> # v5.0+
Reported-by: Tom Burkart <tom@aussec.com>
Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Link: https://lore.kernel.org/r/20201207135959.154124-2-tudor.ambarus@microchip.com
Signed-off-by: Mark Brown <broonie@kernel.org>

spi: atmel-quadspi: Disable clock in probe error path

If the call to of_device_get_match_data() fails on probe of the Atmel
QuadSPI driver, the clock "aq->pclk" is erroneously not unprepared and
disabled. Fix it.

Fixes: 2e5c88887358 ("spi: atmel-quadspi: add support for sam9x60 qspi controller")
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Cc: <stable@vger.kernel.org> # v5.1+
Cc: Tudor Ambarus <tudor.ambarus@microchip.com>
Cc: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Link: https://lore.kernel.org/r/8f8dc2815aa97b2378528f08f923bf81e19611f0.1604874488.git.lukas@wunner.de
Signed-off-by: Mark Brown <broonie@kernel.org>

spi: atmel-quadspi: Use optimezed memcpy_fromio()/memcpy_toio()

Optimezed mem*io operations are defined for LE platforms, use them.

The ARM and !ARCH_EBSA110 dependencies for COMPILE_TEST were added
only for the _memcpy_fromio()/_memcpy_toio() functions. Drop these
dependencies.

Tested unaligned accesses on both sama5d2 and sam9x60 QSPI controllers
using SPI NOR flashes, everything works ok. The following performance
improvement can be seen when running mtd_speedtest:

sama5d2_xplained (mx25l25635e)
- before:
mtd_speedtest: eraseblock write speed is 983 KiB/s
mtd_speedtest: eraseblock read speed is 6150 KiB/s
- after:
mtd_speedtest: eraseblock write speed is 1055 KiB/s
mtd_speedtest: eraseblock read speed is 20144 KiB/s

sam9x60ek (sst26vf064b)
- before:
mtd_speedtest: eraseblock write speed is 4770 KiB/s
mtd_speedtest: eraseblock read speed is 8062 KiB/s
- after:
mtd_speedtest: eraseblock write speed is 4524 KiB/s
mtd_speedtest: eraseblock read speed is 21186 KiB/s

Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Link: https://lore.kernel.org/r/20200716043139.565734-1-tudor.ambarus@microchip.com
Signed-off-by: Mark Brown <broonie@kernel.org>

spi: atmel-quadspi: reject DTR ops

Double Transfer Rate (DTR) ops are added in spi-mem. But this controller
doesn't support DTR transactions. Since we don't use the default
supports_op(), which rejects all DTR ops, do that explicitly in our
supports_op().

Signed-off-by: Pratyush Yadav <p.yadav@ti.com>
Reviewed-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Link: https://lore.kernel.org/r/20200623183030.26591-4-p.yadav@ti.com
Signed-off-by: Mark Brown <broonie@kernel.org>

spi: atmel-quadspi: Add verbose debug facilities to monitor register accesses

This feature should not be enabled in release but can be useful for
developers who need to monitor register accesses at some specific places.

Helped me identify a bug in u-boot, by comparing the register accesses
from the linux driver with the ones from its u-boot variant.

Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Link: https://lore.kernel.org/r/20200320065058.891221-1-tudor.ambarus@microchip.com
Signed-off-by: Mark Brown <broonie@kernel.org>

spi: atmel-quadspi: fix possible MMIO window size overrun

The QSPI controller memory space is limited to 128MB:
0x9000_00000-0x9800_00000/0XD000_0000--0XD800_0000.

There are nor flashes that are bigger in size than the memory size
supported by the controller: Micron MT25QL02G (256 MB).

Check if the address exceeds the MMIO window size. An improvement
would be to add support for regular SPI mode and fall back to it
when the flash memories overrun the controller's memory space.

Fixes: 0e6aae08e9ae ("spi: Add QuadSPI driver for Atmel SAMA5D2")
Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Link: https://lore.kernel.org/r/20200228155437.1558219-1-tudor.ambarus@microchip.com
Signed-off-by: Mark Brown <broonie@kernel.org>

spi: Remove dev_err() usage after platform_get_irq()

We don't need dev_err() messages when platform_get_irq() fails now that
platform_get_irq() prints an error message itself when something goes
wrong. Let's remove these prints with a simple semantic patch.

// <smpl>
@@
expression ret;
struct platform_device *E;
@@

ret =
(
platform_get_irq(E, ...)
|
platform_get_irq_byname(E, ...)
);

if ( \( ret < 0 \| ret <= 0 \) )
{
(
-if (ret != -EPROBE_DEFER)
-{ ...
-dev_err(...);
-... }
|
...
-dev_err(...);
)
...
}
// </smpl>

While we're here, remove braces on if statements that only have one
statement (manually).

Cc: Mark Brown <broonie@kernel.org>
Cc: linux-spi@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Link: https://lore.kernel.org/r/20190730181557.90391-42-swboyd@chromium.org
Signed-off-by: Mark Brown <broonie@kernel.org>

spi: atmel-quadspi: fix resume call

When waking up from the Suspend-to-RAM state, the following error
was seen:

m25p80 spi2.0: flash operation timed out

The flash remained in an undefined state, returning 0xFFs.
Fix it by setting the Serial Clock Baud Rate, as it was set
before the conversion to SPIMEM.

Tested with sama5d2_xplained and mx25l25673g spi-nor in
Backup + Self-Refresh and Suspend modes.

Fixes: 0e6aae08e9ae ("spi: Add QuadSPI driver for Atmel SAMA5D2")
Reported-by: Mark Deneen <mdeneen@gmail.com>
Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

spi: atmel-quadspi: void return type for atmel_qspi_init()

commit 2d30ac5ed633 ("mtd: spi-nor: atmel-quadspi: Use spi-mem interface for atmel-quadspi driver")
removed the error path from atmel_qspi_init(), but not changed the
function's return type. Set void return type for atmel_qspi_init().

Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

spi: atmel-quadspi: fix crash while suspending

atmel_qspi objects are kept in spi_controller objects, so, first get
pointer to spi_controller object and then get atmel_qspi object from
spi_controller object.

Fixes: 2d30ac5ed633 ("mtd: spi-nor: atmel-quadspi: Use spi-mem interface for atmel-quadspi driver")
Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Reviewed-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

spi: atmel-quadspi: Make atmel_qspi_get_name static

Fix sparse warning:

drivers/spi/atmel-quadspi.c:369:12: warning:
symbol 'atmel_qspi_get_name' was not declared. Should it be static?

Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

spi: atmel-quadspi: add support for sam9x60 qspi controller

The sam9x60 qspi controller uses 2 clocks, one for the peripheral register
access, the other for the qspi core and phy. Both are mandatory. It uses
different transfer type bits in IFR register. It has dedicated registers
to specify a read or a write instruction: Read Instruction Code Register
(RICR) and Write Instruction Code Register (WICR). ICR/RICR/WICR have
identical fields.

Tested with sst26vf064b jedec,spi-nor flash. Backward compatibility test
done on sama5d2 qspi controller and mx25l25635e jedec,spi-nor flash.

Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

spi: atmel-quadspi: add support for named peripheral clock

Naming clocks is a good practice. Keep supporting unnamed
peripheral clock, to be backward compatible with old DTs.
While here, rename clk to pclk, to indicate that it is a
peripheral clock.

Suggested-by: Boris Brezillon <bbrezillon@kernel.org>
Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Reviewed-by: Boris Brezillon <bbrezillon@kernel.org>
Signed-off-by: Mark Brown <broonie@kernel.org>

spi: atmel-quadspi: rework transfer macros

Split the TFRTYP_TRSFR_ bitfields in 2: one bit encoding the
mem/reg transfer type and one bit encoding the direction of
the transfer (read/write).

Remove NOP when setting read transfer type. Remove useless
setting of write transfer type when
op->data.dir == SPI_MEM_DATA_IN && !op->data.nbytes.

QSPI_IFR_TFRTYP_TRSFR_WRITE is specific just to sama5d2 qspi,
rename it to QSPI_IFR_SAMA5D2_WRITE_TRSFR.

Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

spi: atmel-quadspi: switch to SPDX license identifiers

Adopt the SPDX license identifiers to ease license compliance
management.

Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Reviewed-by: Boris Brezillon <bbrezillon@kernel.org>
Signed-off-by: Mark Brown <broonie@kernel.org>

spi: atmel-quadspi: return appropriate error code

Return -ENOTSUPP when atmel_qspi_find_mode() fails. Propagate
the error in atmel_qspi_exec_op().

Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Reviewed-by: Boris Brezillon <bbrezillon@kernel.org>
Signed-off-by: Mark Brown <broonie@kernel.org>

spi: atmel-quadspi: remove unnecessary cast

The cast is done implicitly.

Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Reviewed-by: Boris Brezillon <bbrezillon@kernel.org>
Signed-off-by: Mark Brown <broonie@kernel.org>

spi: atmel-quadspi: fix naming scheme

Let general names to core drivers.

Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Reviewed-by: Boris Brezillon <bbrezillon@kernel.org>
Signed-off-by: Mark Brown <broonie@kernel.org>

spi: atmel-quadspi: drop wrappers for iomem accesses

The wrappers hid that the accesses are relaxed. Drop them.

Suggested-by: Boris Brezillon <bbrezillon@kernel.org>
Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Reviewed-by: Boris Brezillon <bbrezillon@kernel.org>
Signed-off-by: Mark Brown <broonie@kernel.org>

spi: atmel-quadspi: order header files inclusion alphabetically

Cosmetic change, no functional change.

Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Reviewed-by: Boris Brezillon <bbrezillon@kernel.org>
Signed-off-by: Mark Brown <broonie@kernel.org>

spi: atmel-quadspi: cache MR value to avoid a write access

Set the controller by default in Serial Memory Mode (SMM) at probe.
Cache Mode Register (MR) value to avoid write access when setting
the controller in serial memory mode at exec_op().

Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

spi: Add QuadSPI driver for Atmel SAMA5D2

Kernel contains QSPI driver strongly tied to MTD and nor-flash memory.
New spi-mem interface allows usage also other memory types, especially
much larger NAND with SPI interface. This driver works as SPI controller
and is not related to MTD, however can work with NAND-flash or other
peripherals using spi-mem interface.

Suggested-by: Boris Brezillon <boris.brezillon@bootlin.com>
Signed-off-by: Piotr Bugalski <bugalski.piotr@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>