On Thu, May 29, 2025 at 07:50:29PM -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.
...
> struct ad7768_state {
> struct iio_trigger *trig;
> struct gpio_desc *gpio_sync_in;
> struct gpio_desc *gpio_reset;
> + bool en_spi_sync;
I'm wondering if moving this...
> const char *labels[ARRAY_SIZE(ad7768_channels)];
> struct gpio_chip gpiochip;
...to here saves a few bytes in accordance to `pahole`.
> };
...
> +static int ad7768_trigger_sources_sync_setup(struct device *dev,
> + struct fwnode_handle *dev_fwnode,
> + struct ad7768_state *st)
> +{
> + struct fwnode_reference_args args;
> +
> + struct fwnode_handle *fwnode __free(fwnode_handle) =
> + fwnode_find_reference_args(dev_fwnode, "trigger-sources",
> + "#trigger-source-cells", 0,
> + AD7768_TRIGGER_SOURCE_SYNC_IDX, &args);
I don't see how args are being used. This puts in doubt the need of the first
patch.
> + if (IS_ERR(fwnode))
> + return PTR_ERR(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");
> + return PTR_ERR_OR_ZERO(st->gpio_sync_in);
> + }
> +
> + /*
> + * 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.
> + */
> + return dev_err_probe(dev, -EOPNOTSUPP, "Invalid synchronization trigger source\n");
> +}
...
> +static int ad7768_trigger_sources_get_sync(struct device *dev,
> + struct ad7768_state *st)
> +{
> + struct fwnode_handle *dev_fwnode = dev_fwnode(dev);
Call it just fwnode.
> + /*
> + * 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(dev_fwnode, "trigger-sources"))
> + return ad7768_trigger_sources_sync_setup(dev, dev_fwnode, st);
> +
> + /*
> + * In the absence of trigger-sources property, enable self
> + * synchronization over SPI (SYNC_OUT).
> + */
> + st->en_spi_sync = true;
> + return 0;
> +}
--
With Best Regards,
Andy Shevchenko
