spi: atmel: Prevent spi transfers from being killed

spi: atmel: Prevent spi transfers from being killed

Upstream commit e0205d6203c2 ("spi: atmel: Prevent false timeouts on
long transfers") has tried to mitigate the problem of getting spi
transfers canceled because they were lasting too long. On slow buses,
transfers in the MiB range can take more than one second and thus a
calculation was added to progressively increment the timeout value. In
order to not be too problematic from a user point of view (waiting dozen
of seconds or even minutes), the wait call was turned interruptible.

Turning the wait interruptible was a mistake as what we really wanted to
do was to be able to kill a transfer. Any signal interrupting our
transfer would not be suitable at all so a second attempt was made at
turning the wait killable instead.

Link: https://lore.kernel.org/linux-spi/20231127095842.389631-1-miquel.raynal@bootlin.com/
All being well, it was reported that JFFS2 was showing a splat when
interrupting a transfer. After some more debate about whether JFFS2
should be fixed and how, it was also pointed out that the whole
consistency of the filesystem in case of parallel I/O would be
compromised. Changing JFFS2 behavior would in theory be possible but
nobody has the energy and time and knowledge to do this now, so better
prevent spi transfers to be interrupted by the user.

Partially revert the blamed commit to no longer use the interruptible
nor the killable variant of wait_for_completion().

Fixes: e0205d6203c2 ("spi: atmel: Prevent false timeouts on long transfers")
Cc:  <stable@vger.kernel.org>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Tested-by: Ronald Wahl <ronald.wahl@raritan.com>
Link: https://lore.kernel.org/r/20231205083102.16946-1-miquel.raynal@bootlin.com
Signed-off-by: Mark Brown <broonie@kernel.org>