spi: offload trigger: add ADI Util Sigma-Delta SPI driver

Add a new driver for the ADI Util Sigma-Delta SPI FPGA IP core.

This is used to trigger a SPI offload based on a RDY signal from an ADC
while masking out other signals on the same line.

Signed-off-by: David Lechner <dlechner@baylibre.com>
Link: https://patch.msgid.link/20250627-iio-adc-ad7173-add-spi-offload-support-v2-9-f49c55599113@baylibre.com
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: dlech

MAINTAINERS

@@ -23413,7 +23413,7 @@ F:	include/linux/mtd/spi-nor.h
 
 SPI OFFLOAD
 R:	David Lechner <dlechner@baylibre.com>
-F:	drivers/spi/spi-offload-trigger-pwm.c
+F:	drivers/spi/spi-offload-trigger-*.c
 F:	drivers/spi/spi-offload.c
 F:	include/linux/spi/offload/
 K:	spi_offload

drivers/spi/Kconfig

@@ -1355,6 +1355,11 @@ if SPI_OFFLOAD
 
 comment "SPI Offload triggers"
 
+config SPI_OFFLOAD_TRIGGER_ADI_UTIL_SD
+	tristate "SPI offload trigger using ADI sigma-delta utility"
+	help
+	  SPI offload trigger from ADI sigma-delta utility FPGA IP block.
+
 config SPI_OFFLOAD_TRIGGER_PWM
 	tristate "SPI offload trigger using PWM"
 	depends on PWM

drivers/spi/Makefile

@@ -170,3 +170,4 @@ obj-$(CONFIG_SPI_SLAVE_SYSTEM_CONTROL)	+= spi-slave-system-control.o
 
 # SPI offload triggers
 obj-$(CONFIG_SPI_OFFLOAD_TRIGGER_PWM)	+= spi-offload-trigger-pwm.o
+obj-$(CONFIG_SPI_OFFLOAD_TRIGGER_ADI_UTIL_SD) += spi-offload-trigger-adi-util-sigma-delta.o

drivers/spi/spi-offload-trigger-adi-util-sigma-delta.c

@@ -0,0 +1,59 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2025 Analog Devices Inc.
+ * Copyright (C) 2025 BayLibre, SAS
+ */
+
+#include <linux/clk.h>
+#include <linux/device.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/property.h>
+#include <linux/spi/offload/provider.h>
+
+static bool adi_util_sigma_delta_match(struct spi_offload_trigger *trigger,
+				       enum spi_offload_trigger_type type,
+				       u64 *args, u32 nargs)
+{
+	return type == SPI_OFFLOAD_TRIGGER_DATA_READY && nargs == 0;
+}
+
+static const struct spi_offload_trigger_ops adi_util_sigma_delta_ops = {
+	.match = adi_util_sigma_delta_match,
+};
+
+static int adi_util_sigma_delta_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct spi_offload_trigger_info info = {
+		.fwnode = dev_fwnode(dev),
+		.ops = &adi_util_sigma_delta_ops,
+	};
+	struct clk *clk;
+
+	clk = devm_clk_get_enabled(dev, NULL);
+	if (IS_ERR(clk))
+		return dev_err_probe(dev, PTR_ERR(clk), "Failed to get clock\n");
+
+	return devm_spi_offload_trigger_register(dev, &info);
+}
+
+static const struct of_device_id adi_util_sigma_delta_of_match_table[] = {
+	{ .compatible = "adi,util-sigma-delta-spi", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, adi_util_sigma_delta_of_match_table);
+
+static struct platform_driver adi_util_sigma_delta_driver = {
+	.probe  = adi_util_sigma_delta_probe,
+	.driver = {
+		.name = "adi-util-sigma-delta-spi",
+		.of_match_table = adi_util_sigma_delta_of_match_table,
+	},
+};
+module_platform_driver(adi_util_sigma_delta_driver);
+
+MODULE_AUTHOR("David Lechner <dlechner@baylibre.com>");
+MODULE_DESCRIPTION("ADI Sigma-Delta SPI offload trigger utility driver");
+MODULE_LICENSE("GPL");