linux-kernel - Re: [PATCH v8 08/11] iio: adc: ad7768-1: add support for Synchronization over SPI

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <aCcFXolH0FVBSP11@smile.fi.intel.com>
Date: Fri, 16 May 2025 12:29:02 +0300
From: Andy Shevchenko <andy@...nel.org>
To: Jonathan Santos <Jonathan.Santos@...log.com>
Cc: linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-gpio@...r.kernel.org,
	nuno.sa@...log.com, Michael.Hennerich@...log.com,
	marcelo.schmitt@...log.com, jic23@...nel.org, robh@...nel.org,
	krzk+dt@...nel.org, conor+dt@...nel.org, marcelo.schmitt1@...il.com,
	linus.walleij@...aro.org, brgl@...ev.pl, lgirdwood@...il.com,
	broonie@...nel.org, jonath4nns@...il.com, dlechner@...libre.com
Subject: Re: [PATCH v8 08/11] iio: adc: ad7768-1: add support for
 Synchronization over SPI

On Thu, May 15, 2025 at 06:13:56PM -0300, Jonathan Santos wrote:
> The synchronization method using GPIO requires the generated pulse to be
> truly synchronous with the base MCLK signal. When it is not possible to
> do that in hardware, the datasheet recommends using synchronization over
> SPI, where the generated pulse is already synchronous with MCLK. This
> requires the SYNC_OUT pin to be connected to the SYNC_IN pin.
> 
> Use trigger-sources property to enable device synchronization over SPI
> and multi-device synchronization while replacing sync-in-gpios property.

...

> +static int ad7768_trigger_sources_get_sync(struct device *dev,
> +					   struct ad7768_state *st)
> +{
> +	struct fwnode_reference_args args;
> +	struct fwnode_handle *fwnode = dev_fwnode(dev);
> +	int ret;
> +
> +	/*
> +	 * The AD7768-1 allows two primary methods for driving the SYNC_IN pin
> +	 * to synchronize one or more devices:
> +	 * 1. Using an external GPIO.
> +	 * 2. Using a SPI command, where the SYNC_OUT pin generates a
> +	 *    synchronization pulse that drives the SYNC_IN pin.
> +	 */
> +	if (!fwnode_property_present(fwnode, "trigger-sources")) {

I'm wondering if you can split the below to a separate function and do something like

	if (fwnode_property_present(...))
		return setup_trigger_source(...);

	...
	en_spi_sync = true;
	return 0;

> +		/*
> +		 * In the absence of trigger-sources property, enable self
> +		 * synchronization over SPI (SYNC_OUT).
> +		 */
> +		st->en_spi_sync = true;
> +		return 0;
> +	}
> +
> +	ret = fwnode_property_get_reference_args(fwnode,
> +						 "trigger-sources",
> +						 "#trigger-source-cells",
> +						 0,
> +						 AD7768_TRIGGER_SOURCE_SYNC_IDX,
> +						 &args);


__free(fwnode_handle) ?

> +	if (ret)
> +		return ret;
> +
> +	fwnode = args.fwnode;
> +	/* First, try getting the GPIO trigger source */
> +	if (fwnode_device_is_compatible(fwnode, "gpio-trigger")) {
> +		st->gpio_sync_in = devm_fwnode_gpiod_get_index(dev, fwnode,
> +							       NULL,
> +							       0,
> +							       GPIOD_OUT_LOW,
> +							       "sync-in");
> +		ret = PTR_ERR_OR_ZERO(st->gpio_sync_in);
> +		goto out_put_node;
> +	}
> +
> +	/*
> +	 * TODO: Support the other cases when we have a trigger subsystem to
> +	 * reliably handle other types of devices as trigger sources.
> +	 *
> +	 * For now, return an error message. For self triggering, omit the
> +	 * trigger-sources property.
> +	 */
> +	ret = dev_err_probe(dev, -EOPNOTSUPP, "Invalid synchronization trigger source\n");
> +
> +out_put_node:

The above will allow to get rid of this label.

> +	fwnode_handle_put(args.fwnode);
> +	return ret;
> +}

-- 
With Best Regards,
Andy Shevchenko