linux-kernel - Re: [PATCH RFC v2 1/8] spi: dt-bindings: spi-peripheral-props: add spi-offloads property

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Message-ID: <20240529-quicksand-pulp-9926fc45a294@wendy>
Date: Wed, 29 May 2024 09:33:10 +0100
From: Conor Dooley <conor.dooley@...rochip.com>
To: Nuno Sá <noname.nuno@...il.com>
CC: Conor Dooley <conor@...nel.org>, David Lechner <dlechner@...libre.com>,
	Mark Brown <broonie@...nel.org>, Jonathan Cameron <jic23@...nel.org>, Rob
 Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor
 Dooley <conor+dt@...nel.org>, Nuno Sá
	<nuno.sa@...log.com>, Michael Hennerich <Michael.Hennerich@...log.com>,
	Lars-Peter Clausen <lars@...afoo.de>, David Jander <david@...tonic.nl>,
	Martin Sperl <kernel@...tin.sperl.org>, <linux-spi@...r.kernel.org>,
	<devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-iio@...r.kernel.org>
Subject: Re: [PATCH RFC v2 1/8] spi: dt-bindings: spi-peripheral-props: add
 spi-offloads property

On Wed, May 29, 2024 at 10:07:37AM +0200, Nuno Sá wrote:
> On Sun, 2024-05-26 at 18:35 +0100, Conor Dooley wrote:
> > On Thu, May 23, 2024 at 02:15:35PM +0200, Nuno Sá wrote:
> > > On Wed, 2024-05-22 at 19:24 +0100, Conor Dooley wrote:
> > 
> > > > 
> > > > To remind myself, "Application 2" featured an offload engine designed
> > > > specifically to work with a particular data format that would strip a
> > > > CRC byte and check the validity of the data stream.
> > > > 
> > > 
> > > I think the data manipulation is not really a property of the engine. Typically
> > > data
> > > going out of the offload engine goes into another "data reorder" block that is
> > > pure
> > > HW.
> > > 
> > > > I think you're right something like that is a stretch to say that that
> > > > is a feature of the SPI controller - but I still don't believe that
> > > > modelling it as part of the ADC is correct. I don't fully understand the
> > > > io-backends and how they work yet, but the features you describe there
> > > > seem like something that should/could be modelled as one, with its own
> > > > node and compatible etc. Describing custom RTL stuff ain't always
> > > > strightforward, but the stuff from Analog is versioned and documented
> > > > etc so it shouldn't be quite that hard.
> > > > 
> > > 
> > > Putting this in io-backends is likely a stretch but one thing to add is that the
> > > peripheral is always (I think) kind of the consumer of the resources.
> > 
> > Could you explain you think why making some additional processing done to
> > the data an io-backend is a stretch? Where else can this RTL be
> > represented? hint: it's not part of the ADC, just like how if you have
> > some custom RTL that does video processing that is not part of the
> > camera!
> 
> Maybe we are speaking about two different things... I do agree with the video
> processing example you gave but for this case I'm not sure there#s any data
> manipulation involved. i mean, there is but nothing controlled by SW at this point.
> Or maybe there's already a future usecase that I'm not aware about (maybe the CRC
> stuff David mentioned).

Yes, this was about the CRC or other additional processing - the quoted
text should really make this clear.

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