spi: bcm63xx-spi: add reset support

bcm63xx arch resets the SPI controller at early boot. However, bmips arch
needs to perform a reset when probing the driver.

Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>
Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Link: https://lore.kernel.org/r/20200616173235.3473149-2-noltari@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-bcm63xx.c

@@ -18,6 +18,7 @@
 #include <linux/err.h>
 #include <linux/pm_runtime.h>
 #include <linux/of.h>
+#include <linux/reset.h>
 
 /* BCM 6338/6348 SPI core */
 #define SPI_6348_RSET_SIZE		64
@@ -493,6 +494,7 @@ static int bcm63xx_spi_probe(struct platform_device *pdev)
 	struct bcm63xx_spi *bs;
 	int ret;
 	u32 num_cs = BCM63XX_SPI_MAX_CS;
+	struct reset_control *reset;
 
 	if (dev->of_node) {
 		const struct of_device_id *match;
@@ -529,6 +531,10 @@ static int bcm63xx_spi_probe(struct platform_device *pdev)
 		return PTR_ERR(clk);
 	}
 
+	reset = devm_reset_control_get_optional_exclusive(dev, NULL);
+	if (IS_ERR(reset))
+		return PTR_ERR(reset);
+
 	master = spi_alloc_master(dev, sizeof(*bs));
 	if (!master) {
 		dev_err(dev, "out of memory\n");
@@ -579,6 +585,12 @@ static int bcm63xx_spi_probe(struct platform_device *pdev)
 	if (ret)
 		goto out_err;
 
+	ret = reset_control_reset(reset);
+	if (ret) {
+		dev_err(dev, "unable to reset device: %d\n", ret);
+		goto out_clk_disable;
+	}
+
 	bcm_spi_writeb(bs, SPI_INTR_CLEAR_ALL, SPI_INT_STATUS);
 
 	/* register and we are done */