linux-kernel - Re: [PATCH v7 14/17] iio: adc: ad4695: Add support for SPI offload

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Message-ID: <ls32gl5a7nsihmmpfabxhm6ilg7idyxdhyrhbkay6e2fiokoah@o5ujfxlsq3s3>
Date: Fri, 17 Jan 2025 16:47:18 +0100
From: Angelo Dureghello <adureghello@...libre.com>
To: David Lechner <dlechner@...libre.com>
Cc: 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>, 
	Uwe Kleine-König <ukleinek@...nel.org>, 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, linux-pwm@...r.kernel.org, 
	Jonathan Cameron <Jonathan.Cameron@...wei.com>
Subject: Re: [PATCH v7 14/17] iio: adc: ad4695: Add support for SPI offload

Hi,

noticed just one possible issue here, see below.

On 13.01.2025 15:00, David Lechner wrote:
> Add support for SPI offload to the ad4695 driver. SPI offload allows
> sampling data at the max sample rate (500kSPS or 1MSPS).
> 
> This is developed and tested against the ADI example FPGA design for
> this family of ADCs [1].
> 
> [1]: http://analogdevicesinc.github.io/hdl/projects/ad469x_fmc/index.html
> 
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> Reviewed-by: Nuno Sa <nuno.sa@...log.com>
> Signed-off-by: David Lechner <dlechner@...libre.com>
> ---
> 
> v7 changes: none
> 
> v6 changes:
> * Fixed use of c++ style comments
> * Moved static const struct definition out of probe function
> * Changes bits_per_word to always be 19 for future oversampling
>   compatibility (Trevor is working on implementing oversampling support
>   on top of this patch, so we have high confidence this is the correct
>   thing to do)
> * Fixed wrong xfer->len
> 
> v5 changes:
> * Register SCLK speed handling has been split out into a separate series.
> * Add sampling_frequency_available attribute.
> * Limit max allowed sampling frequency based on chip info.
> * Expand explanations of offload enable/disable ordering requirements.
> * Finish TODO to use macros for phandle arg values.
> * Don't use dev_info() when falling back to non-offload operation.
> * Update to accommodate changes in other patches in this series.
> 
> v4 changes: new patch in v4
> ---
>  drivers/iio/adc/Kconfig  |   1 +
>  drivers/iio/adc/ad4695.c | 445 +++++++++++++++++++++++++++++++++++++++++++++--
>  2 files changed, 429 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
> index 995b9cacbaa964d26424346120c139858f93cdcd..ec60b64c46e187e2be18ab1f8ca9e6f4f03299f9 100644
> --- a/drivers/iio/adc/Kconfig
> +++ b/drivers/iio/adc/Kconfig
> @@ -52,6 +52,7 @@ config AD4695
>  	tristate "Analog Device AD4695 ADC Driver"
>  	depends on SPI
>  	select IIO_BUFFER
> +	select IIO_BUFFER_DMAENGINE
>  	select IIO_TRIGGERED_BUFFER
>  	select REGMAP
>  	help
> diff --git a/drivers/iio/adc/ad4695.c b/drivers/iio/adc/ad4695.c
> index 13cf01d35301be40369571e7dd2aeac1a8148d15..c8cd73d19e869f11999608f61df5724d329b4427 100644
> --- a/drivers/iio/adc/ad4695.c
> +++ b/drivers/iio/adc/ad4695.c
> @@ -19,14 +19,19 @@
>  #include <linux/device.h>
>  #include <linux/err.h>
>  #include <linux/gpio/consumer.h>
> +#include <linux/iio/buffer-dmaengine.h>
>  #include <linux/iio/buffer.h>
>  #include <linux/iio/iio.h>
>  #include <linux/iio/triggered_buffer.h>
>  #include <linux/iio/trigger_consumer.h>
>  #include <linux/minmax.h>
> +#include <linux/mutex.h>
>  #include <linux/property.h>
> +#include <linux/pwm.h>
>  #include <linux/regmap.h>
>  #include <linux/regulator/consumer.h>
> +#include <linux/spi/offload/consumer.h>
> +#include <linux/spi/offload/provider.h>
>  #include <linux/spi/spi.h>
>  #include <linux/units.h>

...

> +static int ad4695_offload_trigger_request(struct spi_offload_trigger *trigger,
> +					  enum spi_offload_trigger_type type,
> +					  u64 *args, u32 nargs)
> +{
> +	struct ad4695_state *st = spi_offload_trigger_get_priv(trigger);
> +
> +	/* Should already be validated by match, but just in case. */
> +	if (nargs != 2)
> +		return -EINVAL;
> +
> +	/* DT tells us if BUSY event uses GP0 or GP3. */
> +	if (args[1] == AD4695_TRIGGER_PIN_GP3)
> +		return regmap_set_bits(st->regmap, AD4695_REG_GP_MODE,
> +				       AD4695_REG_GP_MODE_BUSY_GP_SEL);
> +
> +	return regmap_clear_bits(st->regmap, AD4695_REG_GPIO_CTRL,
> +				 AD4695_REG_GP_MODE_BUSY_GP_SEL);

This should probably be:
         
        return regmap_clear_bits(st->regmap, AD4695_REG_GPIO_MODE,
                                 AD4695_REG_GP_MODE_BUSY_GP_SEL);

> +}
> +

Regards,
angelo