linux-kernel - Re: [PATCH 01/13] spi: add core support for controllers with offload capabilities

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Message-ID: <aae36622-4e05-4f16-9460-d7614fd599aa@sirena.org.uk>
Date: Thu, 11 Jan 2024 13:33:03 +0000
From: Mark Brown <broonie@...nel.org>
To: Nuno Sá <noname.nuno@...il.com>
Cc: David Lechner <dlechner@...libre.com>,
	Jonathan Cameron <jic23@...nel.org>,
	Rob Herring <robh+dt@...nel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Michael Hennerich <michael.hennerich@...log.com>,
	Nuno Sá <nuno.sa@...log.com>,
	Frank Rowand <frowand.list@...il.com>,
	Thierry Reding <thierry.reding@...il.com>,
	Uwe Kleine-König <u.kleine-koenig@...gutronix.de>,
	Jonathan Corbet <corbet@....net>, linux-spi@...r.kernel.org,
	linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
	linux-doc@...r.kernel.org, linux-pwm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 01/13] spi: add core support for controllers with offload
 capabilities

On Thu, Jan 11, 2024 at 09:49:08AM +0100, Nuno Sá wrote:
> On Wed, 2024-01-10 at 13:49 -0600, David Lechner wrote:

> >     /* in probe() */
> >     offload = spi_offload_get(spi, 0);

> On top of what Mark already stated, and as we already discussed offline, I
> personally don't like this provider - consumer interface for the offload. The
> first thing is that this is taking into account the possibility of having
> multiple offload cores. While the FGPA core was designed with that in mind, we
> don't really have any design using multiple offloads in one spi engine (always
> one). Hence this is all pretty much untested.

I tend to agree that we shouldn't be exposing this to SPI device drivers
however we will want to keep track of if the unit is busy, and designing
it to cope with multiple offloads does seem like sensible future
proofing.  There's also the possibility that one engine might be able to
cope with multiple scripts being active at once (eg, triggering a
different action depending on the trigger).

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