The GPIO silicon is clocked with a PCLK (peripheral clock)
on all systems, however not all platforms model it and include
it in e.g. the device tree, so add clock handling but make it
optional so we bail out safely if it is e.g. always on.

Signed-off-by: Linus Walleij <redacted>
---
ChangeLog v1->v2:
- Bail out properly for -EPROBE_DEFER from the clock.
---
 drivers/gpio/gpio-ftgpio010.c | 41 +++++++++++++++++++++++++++++++----
 1 file changed, 37 insertions(+), 4 deletions(-)

diff --git a/drivers/gpio/gpio-ftgpio010.c b/drivers/gpio/gpio-ftgpio010.c
index 868bf8501560..f548bc92e1d1 100644
--- a/drivers/gpio/gpio-ftgpio010.c
+++ b/drivers/gpio/gpio-ftgpio010.c

@@ -15,6 +15,7 @@
 #include <linux/interrupt.h>
 #include <linux/platform_device.h>
 #include <linux/bitops.h>
+#include <linux/clk.h>
 
 /* GPIO registers definition */
 #define GPIO_DATA_OUT		0x00

@@ -40,11 +41,14 @@
  * struct ftgpio_gpio - Gemini GPIO state container
  * @dev: containing device for this instance
  * @gc: gpiochip for this instance
+ * @base: remapped I/O-memory base
+ * @clk: silicon clock
  */
 struct ftgpio_gpio {
 	struct device *dev;
 	struct gpio_chip gc;
 	void __iomem *base;
+	struct clk *clk;
 };
 
 static void ftgpio_gpio_ack_irq(struct irq_data *d)

@@ -180,6 +184,19 @@ static int ftgpio_gpio_probe(struct platform_device *pdev)
 	if (irq <= 0)
 		return irq ? irq : -EINVAL;
 
+	g->clk = devm_clk_get(dev, NULL);
+	if (!IS_ERR(g->clk)) {
+		ret = clk_prepare_enable(g->clk);
+		if (ret)
+			return ret;
+	} else if (PTR_ERR(g->clk) == -EPROBE_DEFER) {
+		/*
+		 * Percolate deferrals, for anything else,
+		 * just live without the clocking.
+		 */
+		return PTR_ERR(g->clk);