linux-kernel - Re: [PATCH 3/3] iio: adc: ad7606: add SPI offload support

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Message-ID: <20250405164041.7d2e586b@jic23-huawei>
Date: Sat, 5 Apr 2025 16:40:41 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: Angelo Dureghello <adureghello@...libre.com>
Cc: Lars-Peter Clausen <lars@...afoo.de>, Michael Hennerich
 <Michael.Hennerich@...log.com>, Rob Herring <robh@...nel.org>, Krzysztof
 Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>,
 Jonathan Corbet <corbet@....net>, David Lechner <dlechner@...libre.com>,
 linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org
Subject: Re: [PATCH 3/3] iio: adc: ad7606: add SPI offload support

On Thu, 03 Apr 2025 18:19:06 +0200
Angelo Dureghello <adureghello@...libre.com> wrote:

> From: Angelo Dureghello <adureghello@...libre.com>
> 
> Add SPI offload support for this family.
> 
> Signed-off-by: Angelo Dureghello <adureghello@...libre.com>
Hi Angelo,

Code looks fine, but there is a TODO I'd like to know more about
as it sounds 'ominous'. 

Otherwise this needs a dt review for patch 1 before I queue it up.

Jonathan
> diff --git a/drivers/iio/adc/ad7606_spi.c b/drivers/iio/adc/ad7606_spi.c
> index b2b975fb7fea4d1af6caef59e75ca495501bc140..b086122497eb22042171580878160334f56baa23 100644
> --- a/drivers/iio/adc/ad7606_spi.c
> +++ b/drivers/iio/adc/ad7606_spi.c

> +static int ad7606_spi_offload_probe(struct device *dev,
> +				    struct iio_dev *indio_dev)
> +{
> +	struct ad7606_state *st = iio_priv(indio_dev);
> +	struct spi_device *spi = to_spi_device(dev);
> +	struct spi_bus_data *bus_data;
> +	struct dma_chan *rx_dma;
> +	struct spi_offload_trigger_info trigger_info = {
> +		.fwnode = dev_fwnode(dev),
> +		.ops = &ad7606_offload_trigger_ops,
> +		.priv = st,
> +	};
> +	int ret;
> +
> +	bus_data = devm_kzalloc(dev, sizeof(*bus_data), GFP_KERNEL);
> +	if (!bus_data)
> +		return -ENOMEM;
> +	st->bus_data = bus_data;
> +
> +	bus_data->offload = devm_spi_offload_get(dev, spi,
> +						 &ad7606_spi_offload_config);
> +	ret = PTR_ERR_OR_ZERO(bus_data->offload);
> +	if (ret && ret != -ENODEV)
> +		return dev_err_probe(dev, ret, "failed to get SPI offload\n");
> +	/* Allow main ad7606_probe function to continue. */
> +	if (ret == -ENODEV)
> +		return 0;
> +
> +	ret = devm_spi_offload_trigger_register(dev, &trigger_info);
> +	if (ret)
> +		return dev_err_probe(dev, ret,
> +				     "failed to register offload trigger\n");
> +
> +	bus_data->offload_trigger = devm_spi_offload_trigger_get(dev,
> +		bus_data->offload, SPI_OFFLOAD_TRIGGER_DATA_READY);
> +	if (IS_ERR(bus_data->offload_trigger))
> +		return dev_err_probe(dev, PTR_ERR(bus_data->offload_trigger),
> +				     "failed to get offload trigger\n");
> +
> +	/* TODO: PWM setup should be ok, done for the backend. PWM mutex ? */

I don't understand this todo. Perhaps some more details?

> +	rx_dma = devm_spi_offload_rx_stream_request_dma_chan(dev,
> +							     bus_data->offload);
> +	if (IS_ERR(rx_dma))
> +		return dev_err_probe(dev, PTR_ERR(rx_dma),
> +				     "failed to get offload RX DMA\n");
> +
> +	ret = devm_iio_dmaengine_buffer_setup_with_handle(dev, indio_dev,
> +		rx_dma, IIO_BUFFER_DIRECTION_IN);
> +	if (ret)
> +		return dev_err_probe(dev, PTR_ERR(rx_dma),
> +				     "failed to setup offload RX DMA\n");
> +
> +	/* Use offload ops. */
> +	indio_dev->setup_ops = &ad7606_offload_buffer_setup_ops;
> +
> +	st->offload_en = true;
> +
> +	return 0;
> +}