linux-kernel - Re: [PATCH v3 3/6] spi: spi-fsl-dspi: Stub out DMA functions

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Message-ID: <aF0wRFKOkejfvuYT@finisterre.sirena.org.uk>
Date: Thu, 26 Jun 2025 12:34:28 +0100
From: Mark Brown <broonie@...nel.org>
To: James Clark <james.clark@...aro.org>
Cc: Arnd Bergmann <arnd@...db.de>, Frank Li <Frank.li@....com>,
	Vladimir Oltean <olteanv@...il.com>,
	Vladimir Oltean <vladimir.oltean@....com>,
	Larisa Grigore <larisa.grigore@....com>,
	Christoph Hellwig <hch@....de>, linux-spi@...r.kernel.org,
	imx@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 3/6] spi: spi-fsl-dspi: Stub out DMA functions

On Thu, Jun 26, 2025 at 11:04:50AM +0100, James Clark wrote:
> On 25/06/2025 11:54 am, Arnd Bergmann wrote:

> > In theory you may also want to turn off DMA mode for testing,
> > which is supported by at least the DW_DMA driver.

> > I see that SPI_TEGRA114 has a dependency on TEGRA20_APB_DMA,
> > which is yet another variation. This is clearly done for
> > usability purposes since that SPI driver only ever works with
> > the specific DMA driver in practice, but it seems worse
> > conceptually.

> I can add it, I'm just questioning the usefulness of adding a new config
> option that's unlikely to be used in reality. It only achieves the same
> thing as doing #if CONFIG_DMA_ENGINE in one place in the code.

> Ultimately we're just trying to fix some randconfig error, if we start
> adding new knobs for people to turn just do that, there's a risk they won't
> get used and we'll make configuring more complicated for people.

Please just keep things simple, as you say nobody is likely to be
actually trying to run such a configuration practically.

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