There are controllers not able to just read data cycles on the
bus. There are controllers not able to do a change column.
If we want to support both, we need to check which operation is
supported first. This is the exact same mechanism that is in use for
parameter page reads (ONFI/JEDEC) as the same problem occurs.
Speed testing does not show any throughput penalty so we do not
optimize more than that. However it is likely that, in the future, a
more robust and exhaustive test will run at boot time to avoid
re-checking what is supported and what is not at every call.
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Link: https://lore.kernel.org/linux-mtd/20200519130834.2918-1-miquel.raynal@bootlin.com
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