[PATCH v3 1/2] spi: spi-cadence: Add optional reset control support

[Ji Sheng Teoh <jisheng.teoh@xxxxxxxxxxxxxxxx>]

Add optional reset control support for spi-cadence to properly bring
the SPI device into an operating condition.

Co-developed-by: Eng Lee Teh <englee.teh@xxxxxxxxxxxxxxxx>
Signed-off-by: Eng Lee Teh <englee.teh@xxxxxxxxxxxxxxxx>
Co-developed-by: Ley Foon Tan <leyfoon.tan@xxxxxxxxxxxxxxxx>
Signed-off-by: Ley Foon Tan <leyfoon.tan@xxxxxxxxxxxxxxxx>
Signed-off-by: Ji Sheng Teoh <jisheng.teoh@xxxxxxxxxxxxxxxx>
---
 drivers/spi/spi-cadence.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/spi/spi-cadence.c b/drivers/spi/spi-cadence.c
index e5140532071d..4eacf3f6e031 100644
--- a/drivers/spi/spi-cadence.c
+++ b/drivers/spi/spi-cadence.c
@@ -18,6 +18,7 @@
 #include <linux/of_address.h>
 #include <linux/platform_device.h>
 #include <linux/pm_runtime.h>
+#include <linux/reset.h>
 #include <linux/spi/spi.h>
 
 /* Name of this driver */
@@ -111,6 +112,7 @@
  * @dev_busy:		Device busy flag
  * @is_decoded_cs:	Flag for decoder property set or not
  * @tx_fifo_depth:	Depth of the TX FIFO
+ * @rstc:		Optional reset control for SPI controller
  */
 struct cdns_spi {
 	void __iomem *regs;
@@ -125,6 +127,7 @@ struct cdns_spi {
 	u8 dev_busy;
 	u32 is_decoded_cs;
 	unsigned int tx_fifo_depth;
+	struct reset_control *rstc;
 };
 
 /* Macros for the SPI controller read/write */
@@ -588,6 +591,16 @@ static int cdns_spi_probe(struct platform_device *pdev)
 		goto remove_ctlr;
 	}
 
+	xspi->rstc = devm_reset_control_get_optional_exclusive(&pdev->dev, "spi");
+	if (IS_ERR(xspi->rstc)) {
+		ret = dev_err_probe(&pdev->dev, PTR_ERR(xspi->rstc),
+				    "Cannot get SPI reset.\n");
+		goto remove_ctlr;
+	}
+
+	reset_control_assert(xspi->rstc);
+	reset_control_deassert(xspi->rstc);
+
 	if (!spi_controller_is_target(ctlr)) {
 		xspi->ref_clk = devm_clk_get_enabled(&pdev->dev, "ref_clk");
 		if (IS_ERR(xspi->ref_clk)) {
-- 
2.43.2