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	Wed, 08 May 2024 15:44:53 +0200
Date: Wed, 8 May 2024 15:44:53 +0200
From: Martin Kaiser <martin@kaiser.cx>
To: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= <u.kleine-koenig@pengutronix.de>
Cc: Mark Brown <broonie@kernel.org>, Shawn Guo <shawnguo@kernel.org>,
	Sascha Hauer <s.hauer@pengutronix.de>,
	Pengutronix Kernel Team <kernel@pengutronix.de>,
	Fabio Estevam <festevam@gmail.com>,
	Alexander Stein <alexander.stein@ew.tq-group.com>,
	Francesco Dolcini <francesco.dolcini@toradex.com>,
	linux-spi@vger.kernel.org, imx@lists.linux.dev,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] spi: imx: Don't expect DMA for i.MX{25,35,50,51,53} cspi
 devices
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References: <20240508095610.2146640-2-u.kleine-koenig@pengutronix.de>
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Sender: "Martin Kaiser,,," <martin@akranes.kaiser.cx>

Hi Uwe,

Thus wrote Uwe Kleine-König (u.kleine-koenig@pengutronix.de):

> While in commit 2dd33f9cec90 ("spi: imx: support DMA for imx35") it was
> claimed that DMA works on i.MX25, i.MX31 and i.MX35 the respective
> device trees don't add DMA channels. The Reference manuals of i.MX31 and
> i.MX25 also don't mention the CSPI core being DMA capable. (I didn't
> check the others.)

If I'm not mistaken, the imx25 reference manual

https://www.nxp.com/docs/en/reference-manual/IMX25RM.pdf

does say that CSPI has DMA support. Section 18.1.1 (Features) lists DMA as one
of the features. There's also DMA events (section 3) for CSPI-1/2/3 RX, TX.

I'd have to dig up the hardware to test again if this is actually working...

   Martin