linux-kernel - Re: [PATCH 12/13] iio: offload: add new PWM triggered DMA buffer driver

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Message-ID: <00c5f84a4bc5a4e3423f401af7b4f374c930407d.camel@gmail.com>
Date: Thu, 11 Jan 2024 10:31:15 +0100
From: Nuno Sá <noname.nuno@...il.com>
To: David Lechner <dlechner@...libre.com>, Mark Brown <broonie@...nel.org>, 
 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>
Cc: 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 12/13] iio: offload: add new PWM triggered DMA buffer
 driver

On Wed, 2024-01-10 at 13:49 -0600, David Lechner wrote:
> This adds a new driver for handling SPI offloading using a PWM as the
> trigger and DMA for the received data. This will be used by ADCs in
> conjunction with SPI controllers with offloading support to be able
> to sample at high rates without CPU intervention.
> 
> Signed-off-by: David Lechner <dlechner@...libre.com>
> ---
>  drivers/iio/Kconfig                                |   1 +
>  drivers/iio/Makefile                               |   1 +
>  .../iio/buffer/industrialio-hw-triggered-buffer.c  |   1 +
>  drivers/iio/offload/Kconfig                        |  21 ++
>  drivers/iio/offload/Makefile                       |   2 +
>  drivers/iio/offload/iio-pwm-triggered-dma-buffer.c | 212
> +++++++++++++++++++++
>  6 files changed, 238 insertions(+)
> 
> diff --git a/drivers/iio/Kconfig b/drivers/iio/Kconfig
> index 52eb46ef84c1..56738282d82f 100644
> --- a/drivers/iio/Kconfig
> +++ b/drivers/iio/Kconfig
> @@ -90,6 +90,7 @@ source "drivers/iio/imu/Kconfig"
>  source "drivers/iio/light/Kconfig"
>  source "drivers/iio/magnetometer/Kconfig"
>  source "drivers/iio/multiplexer/Kconfig"
> +source "drivers/iio/offload/Kconfig"

The offload stuff is something very particular to a spi controller feature. Not
sure if having this as a generic thing makes sense at this point.

IMO, the IIO way of looking at the offload engine is as an HW triggered core for
capturing data. Hence, I would support the whole thing as an HW triggered
buffer. And, if we are really going the path of having the offload core as a
platform device, we could have different compatibles for each pair of trigger +
data_capture (or explicit dt properties).

Just my 2 cents...

- Nuno Sá