linux-kernel - Re: [PATCH] spi: dt-bindings: samsung: make dma properties not required

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Date: Fri, 1 Mar 2024 20:42:39 +0000
From: Mark Brown <broonie@...nel.org>
To: Sam Protsenko <semen.protsenko@...aro.org>
Cc: Tudor Ambarus <tudor.ambarus@...aro.org>, andi.shyti@...nel.org,
	robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
	conor+dt@...nel.org, linux-spi@...r.kernel.org,
	linux-samsung-soc@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, andre.draszik@...aro.org,
	peter.griffin@...aro.org, willmcvicker@...gle.com,
	kernel-team@...roid.com
Subject: Re: [PATCH] spi: dt-bindings: samsung: make dma properties not
 required

On Fri, Mar 01, 2024 at 01:28:35PM -0600, Sam Protsenko wrote:
> On Fri, Mar 1, 2024 at 5:55 AM Tudor Ambarus <tudor.ambarus@...aro.org> wrote:

> > Since the addition of the driver in 2009, the driver selects between DMA
> > and polling mode depending on the transfer length - DMA mode for
> > transfers bigger than the FIFO depth, polling mode otherwise. All
> > versions of the IP support polling mode, make the dma properties not
> > required.

> AFAIU, the device tree has nothing to do with drivers, it's about
> hardware description. Does making DMA properties not required here
> mean that there are some HW out there which doesn't integrate DMA in
> SPI blocks? Even if this change is ok (I'm not sure), the
> argumentation doesn't look sound to me.

I do remember there being some SoC which shipped a SPI controller in
that configuration for some reason.  Possibly one of the OEM ones rather
than one in a Samsung SoC?

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