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Message-ID: <5b62d742fa789e9860781b6f5f1fda4f583b0e5b.camel@gmail.com>
Subject: Re: [PATCH 01/13] spi: add core support for controllers with
 offload capabilities
From: Nuno =?ISO-8859-1?Q?S=E1?= <noname.nuno@gmail.com>
To: Mark Brown <broonie@kernel.org>
Cc: David Lechner <dlechner@baylibre.com>, Jonathan Cameron
 <jic23@kernel.org>,  Rob Herring <robh+dt@kernel.org>, Krzysztof Kozlowski
 <krzysztof.kozlowski+dt@linaro.org>, Conor Dooley <conor+dt@kernel.org>,
 Michael Hennerich <michael.hennerich@analog.com>,  Nuno
 =?ISO-8859-1?Q?S=E1?= <nuno.sa@analog.com>, Frank Rowand
 <frowand.list@gmail.com>, Thierry Reding <thierry.reding@gmail.com>, Uwe
 =?ISO-8859-1?Q?Kleine-K=F6nig?= <u.kleine-koenig@pengutronix.de>, Jonathan
 Corbet <corbet@lwn.net>,  linux-spi@vger.kernel.org,
 linux-iio@vger.kernel.org, devicetree@vger.kernel.org, 
 linux-doc@vger.kernel.org, linux-pwm@vger.kernel.org, 
 linux-kernel@vger.kernel.org
Date: Thu, 11 Jan 2024 15:11:32 +0100
In-Reply-To: <aae36622-4e05-4f16-9460-d7614fd599aa@sirena.org.uk>
References: 
	<20240109-axi-spi-engine-series-3-v1-0-e42c6a986580@baylibre.com>
	 <20240109-axi-spi-engine-series-3-v1-1-e42c6a986580@baylibre.com>
	 <0c0b1954825dc174cab48060e96ddadadc18aefd.camel@gmail.com>
	 <aae36622-4e05-4f16-9460-d7614fd599aa@sirena.org.uk>
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On Thu, 2024-01-11 at 13:33 +0000, Mark Brown wrote:
> On Thu, Jan 11, 2024 at 09:49:08AM +0100, Nuno S=C3=A1 wrote:
> > On Wed, 2024-01-10 at 13:49 -0600, David Lechner wrote:
>=20
> > > =C2=A0=C2=A0=C2=A0 /* in probe() */
> > > =C2=A0=C2=A0=C2=A0 offload =3D spi_offload_get(spi, 0);
>=20
> > On top of what Mark already stated, and as we already discussed offline=
, I
> > personally don't like this provider - consumer interface for the offloa=
d.
> > The
> > first thing is that this is taking into account the possibility of havi=
ng
> > multiple offload cores. While the FGPA core was designed with that in m=
ind,
> > we
> > don't really have any design using multiple offloads in one spi engine
> > (always
> > one). Hence this is all pretty much untested.
>=20
> 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.=C2=A0 There's also the possibility that one engine might be abl=
e to

Fair enough. But wouldn't a simple DT integer property (handled by the spi =
core)
to identify the offload index be easier for SPI device drivers? We could st=
ill
have dedicated interfaces for checking if the unit is busy or not... The po=
int
is that we would not need an explicit get() from SPI drivers.

I'm of course assuming that one spi device can only be connected to one eng=
ine
which seems reasonable to me.

- Nuno S=C3=A1