[PATCH 18/22] mtd: rawnand: Choose the best timings, NV-DDR included

[Miquel Raynal]

On Wed, 2021-05-05 at 21:37:46 UTC, Miquel Raynal wrote:
> Now that the necessary peaces to support the NV-DDR interface type have
> been contributed, let's add the relevant logic to make use of it. In
> particular, the core does not choose the best SDR timings anymore but
> calls a more generic helper instead.
> 
> This helper checks if NV-DDR is supported by trying to find the best
> NV-DDR supported mode through a logic very close to what is being done
> for SDR timings. If no NV-DDR mode in common between the NAND controller
> and the NAND chip is found, the core will fallback to SDR.
> 
> Side note: theoretically, the data clock speed in NV-DDR mode 0 is
> slower than in SDR mode 5. In the situation where we would get a working
> NV-DDR mode 0, we could also try if SDR mode 5 is supported and
> eventually fallback to it in order to get the fastest possible
> throughput. However, in the field, it looks like most of the devices
> supporting NV-DDR avoid implementing the fastest SDR modes (like 4 and 5
> EDO modes, which are a bit more complicated to handle than the other SDR
> modes). So, we will stick to the simplest logic: try NV-DDR otherwise
> fallback to SDR. If someone else experiences strong differences because
> of that we may still implement the logic defined above.
> 
> Signed-off-by: Miquel Raynal <miquel.raynal at bootlin.com>

Applied to https://git.kernel.org/pub/scm/linux/kernel/git/mtd/linux.git nand/next.

Miquel