[PATCH v2 3/3] spi: dw: Add support for an optional interface clock

[Gareth Williams <gareth.williams.jx@xxxxxxxxxxx>]

From: Phil Edworthy <phil.edworthy@xxxxxxxxxxx>

The Synopsys SSI Controller has an interface clock, but most SoCs hide
this away. However, on some SoCs you need to explicitly enable the
interface clock in order to access the registers. Therefore, add support
for an optional interface clock.

Signed-off-by: Phil Edworthy <phil.edworthy@xxxxxxxxxxx>
Signed-off-by: Gareth Williams <gareth.williams.jx@xxxxxxxxxxx>
---
v2:
 - Added dependancy information to patch notes.
 - Expanded on optional clock comment for clarity

Depends on commit 60b8f0ddf1a ("clk: Add (devm_)clk_get_optional()
functions")
---
 drivers/spi/spi-dw-mmio.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/spi/spi-dw-mmio.c b/drivers/spi/spi-dw-mmio.c
index 4bd59a9..de952b1 100644
--- a/drivers/spi/spi-dw-mmio.c
+++ b/drivers/spi/spi-dw-mmio.c
@@ -30,6 +30,7 @@
 struct dw_spi_mmio {
 	struct dw_spi  dws;
 	struct clk     *clk;
+	struct clk     *pclk;
 	void           *priv;
 };
 
@@ -172,6 +173,14 @@ static int dw_spi_mmio_probe(struct platform_device *pdev)
 	if (ret)
 		return ret;
 
+	/* Optional clock needed to access the registers */
+	dwsmmio->pclk = devm_clk_get_optional(&pdev->dev, "pclk");
+	if (IS_ERR(dwsmmio->pclk))
+		return PTR_ERR(dwsmmio->pclk);
+	ret = clk_prepare_enable(dwsmmio->pclk);
+	if (ret)
+		goto out_clk;
+
 	dws->bus_num = pdev->id;
 
 	dws->max_freq = clk_get_rate(dwsmmio->clk);
@@ -199,6 +208,8 @@ static int dw_spi_mmio_probe(struct platform_device *pdev)
 	return 0;
 
 out:
+	clk_disable_unprepare(dwsmmio->pclk);
+out_clk:
 	clk_disable_unprepare(dwsmmio->clk);
 	return ret;
 }
@@ -208,6 +219,7 @@ static int dw_spi_mmio_remove(struct platform_device *pdev)
 	struct dw_spi_mmio *dwsmmio = platform_get_drvdata(pdev);
 
 	dw_spi_remove_host(&dwsmmio->dws);
+	clk_disable_unprepare(dwsmmio->pclk);
 	clk_disable_unprepare(dwsmmio->clk);
 
 	return 0;
-- 
2.7.4