[PATCHv2] mtd: spi-nor: cadence-quadspi: add reset control

[Dinh Nguyen]

Get the reset control for the QSPI controller and bring it out of reset.

Suggested-by: Tien-Fong Chee <tien.fong.chee@xxxxxxxxx>
Signed-off-by: Dinh Nguyen <dinguyen@xxxxxxxxxx>
---
v2: use devm_reset_control_get_optional_exclusive
    print an error message
    return -EPROBE_DEFER
---
 drivers/mtd/spi-nor/cadence-quadspi.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/mtd/spi-nor/cadence-quadspi.c b/drivers/mtd/spi-nor/cadence-quadspi.c
index 792628750eec..c548567adcf0 100644
--- a/drivers/mtd/spi-nor/cadence-quadspi.c
+++ b/drivers/mtd/spi-nor/cadence-quadspi.c
@@ -34,6 +34,7 @@
 #include <linux/of.h>
 #include <linux/platform_device.h>
 #include <linux/pm_runtime.h>
+#include <linux/reset.h>
 #include <linux/sched.h>
 #include <linux/spi/spi.h>
 #include <linux/timer.h>
@@ -1336,6 +1337,7 @@ static int cqspi_probe(struct platform_device *pdev)
 	struct cqspi_st *cqspi;
 	struct resource *res;
 	struct resource *res_ahb;
+	struct reset_control *rstc;
 	const struct cqspi_driver_platdata *ddata;
 	int ret;
 	int irq;
@@ -1362,6 +1364,18 @@ static int cqspi_probe(struct platform_device *pdev)
 		return PTR_ERR(cqspi->clk);
 	}
 
+	/* Obtain QSPI reset control */
+	rstc = devm_reset_control_get_optional_exclusive(dev, NULL);
+	if (IS_ERR(rstc)) {
+		dev_err(dev, "Cannot get QSPI reset.\n");
+		if (PTR_ERR(rstc) == -EPROBE_DEFER)
+			return -EPROBE_DEFER;
+	} else {
+		reset_control_assert(rstc);
+		udelay(1);
+		reset_control_deassert(rstc);
+	}
+
 	/* Obtain and remap controller address. */
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	cqspi->iobase = devm_ioremap_resource(dev, res);
-- 
2.20.0