spi: axi-spi-engine: wait for completion in setup

Add a polling wait for SPI instruction execution to complete in the
spi_engine_setup() function. In practice, these instructions complete
in a few 10s of nanoseconds, so we never ran into any race conditions,
but it is good practice to wait for the completion of the SPI engine
instructions before returning from the setup function.

Signed-off-by: David Lechner <dlechner@baylibre.com>
Link: https://patch.msgid.link/20250428-adi-main-v1-1-4b8a1b88a212@baylibre.com
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: dlech

drivers/spi/spi-axi-spi-engine.c

@@ -14,6 +14,7 @@
 #include <linux/fpga/adi-axi-common.h>
 #include <linux/interrupt.h>
 #include <linux/io.h>
+#include <linux/iopoll.h>
 #include <linux/of.h>
 #include <linux/module.h>
 #include <linux/overflow.h>
@@ -739,12 +740,16 @@ static int spi_engine_setup(struct spi_device *device)
 {
 	struct spi_controller *host = device->controller;
 	struct spi_engine *spi_engine = spi_controller_get_devdata(host);
+	unsigned int reg;
 
 	if (device->mode & SPI_CS_HIGH)
 		spi_engine->cs_inv |= BIT(spi_get_chipselect(device, 0));
 	else
 		spi_engine->cs_inv &= ~BIT(spi_get_chipselect(device, 0));
 
+	writel_relaxed(SPI_ENGINE_CMD_SYNC(0),
+		       spi_engine->base + SPI_ENGINE_REG_CMD_FIFO);
+
 	writel_relaxed(SPI_ENGINE_CMD_CS_INV(spi_engine->cs_inv),
 		       spi_engine->base + SPI_ENGINE_REG_CMD_FIFO);
 
@@ -755,7 +760,11 @@ static int spi_engine_setup(struct spi_device *device)
 	writel_relaxed(SPI_ENGINE_CMD_ASSERT(0, 0xff),
 		       spi_engine->base + SPI_ENGINE_REG_CMD_FIFO);
 
-	return 0;
+	writel_relaxed(SPI_ENGINE_CMD_SYNC(1),
+		       spi_engine->base + SPI_ENGINE_REG_CMD_FIFO);
+
+	return readl_relaxed_poll_timeout(spi_engine->base + SPI_ENGINE_REG_SYNC_ID,
+					  reg, reg == 1, 1, 1000);
 }
 
 static int spi_engine_transfer_one_message(struct spi_controller *host,