[RFC PATCH 01/10] spi: spi-mem: Introduce support for tuning controller

[Mark Brown]

On Tue, Aug 12, 2025 at 01:02:10AM +0530, Santhosh Kumar K wrote:
> From: Pratyush Yadav <pratyush at kernel.org>
> 
> Some controllers like the Cadence OSPI controller need to perform a
> tuning sequence to operate at high data rates. Tuning is needs to happen
> once the device is switched to appropriate mode (say 8S-8S-8S or
> 8D-8D-8D). Add a hook that spi-mem client devices can call in order to tune
> the controller to operate in a given mode and data rate.
> 
> This is somewhat similar to eMMC/SD tuning for higher speed modes like
> HS200, but there isn't a standard specification around the same though.

Should we have something that blocks these tuning required modes without
the appropriate tuning, and/or allows discovery of which modes require
this tuning?  This all feels very landmineish - client drivers just have
to know when tuning is required.
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