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

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Message-ID: <6c35baad-a332-4b0a-96ca-1cdb3840ad94@sirena.org.uk>
Date: Wed, 13 Aug 2025 21:26:06 +0100
From: Mark Brown <broonie@...nel.org>
To: Santhosh Kumar K <s-k6@...com>
Cc: miquel.raynal@...tlin.com, richard@....at, vigneshr@...com,
	tudor.ambarus@...aro.org, pratyush@...nel.org, mwalle@...nel.org,
	p-mantena@...com, linux-spi@...r.kernel.org,
	linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org,
	a-dutta@...com, u-kumar1@...com, praneeth@...com
Subject: Re: [RFC PATCH 01/10] spi: spi-mem: Introduce support for tuning
 controller

On Tue, Aug 12, 2025 at 01:02:10AM +0530, Santhosh Kumar K wrote:
> From: Pratyush Yadav <pratyush@...nel.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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