[PATCH v2 2/2] gpio: ixp4xx: Handle clock output on pin 14 and 15

[Linus Walleij <linus.walleij@xxxxxxxxxx>]

This makes it possible to provide basic clock output on pins
14 and 15. The clocks are typically used by random electronics,
not modeled in the device tree, so they just need to be provided
on request.

Signed-off-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
---
 drivers/gpio/gpio-ixp4xx.c | 40 ++++++++++++++++++++++++++++++++++++++--
 1 file changed, 38 insertions(+), 2 deletions(-)

diff --git a/drivers/gpio/gpio-ixp4xx.c b/drivers/gpio/gpio-ixp4xx.c
index dde6cf3a5779..d69954d19144 100644
--- a/drivers/gpio/gpio-ixp4xx.c
+++ b/drivers/gpio/gpio-ixp4xx.c
@@ -38,6 +38,18 @@
 #define IXP4XX_GPIO_STYLE_MASK		GENMASK(2, 0)
 #define IXP4XX_GPIO_STYLE_SIZE		3
 
+/*
+ * Clock output control register defines.
+ */
+#define IXP4XX_GPCLK_CLK0DC_SHIFT	0
+#define IXP4XX_GPCLK_CLK0TC_SHIFT	4
+#define IXP4XX_GPCLK_CLK0_MASK		GENMASK(7, 0)
+#define IXP4XX_GPCLK_MUX14		BIT(8)
+#define IXP4XX_GPCLK_CLK1DC_SHIFT	16
+#define IXP4XX_GPCLK_CLK1TC_SHIFT	20
+#define IXP4XX_GPCLK_CLK1_MASK		GENMASK(23, 16)
+#define IXP4XX_GPCLK_MUX15		BIT(24)
+
 /**
  * struct ixp4xx_gpio - IXP4 GPIO state container
  * @dev: containing device for this instance
@@ -202,6 +214,7 @@ static int ixp4xx_gpio_probe(struct platform_device *pdev)
 	struct ixp4xx_gpio *g;
 	struct gpio_irq_chip *girq;
 	struct device_node *irq_parent;
+	u32 val;
 	int ret;
 
 	g = devm_kzalloc(dev, sizeof(*g), GFP_KERNEL);
@@ -227,11 +240,34 @@ static int ixp4xx_gpio_probe(struct platform_device *pdev)
 
 	/*
 	 * Make sure GPIO 14 and 15 are NOT used as clocks but GPIO on
-	 * specific machines.
+	 * specific machines. For others, use the boot defaults as
+	 * starting point.
 	 */
 	if (of_machine_is_compatible("dlink,dsm-g600-a") ||
 	    of_machine_is_compatible("iom,nas-100d"))
-		__raw_writel(0x0, g->base + IXP4XX_REG_GPCLK);
+		val = 0;
+	else
+		val = __raw_readl(g->base + IXP4XX_REG_GPCLK);
+
+	/*
+	 * Enable clock outputs with default timings of requested clock.
+	 * If you need control over TC and DC, add these to the device
+	 * tree bindings and use them here.
+	 */
+	if (of_property_read_bool(np, "intel,ixp4xx-gpio14-clkout")) {
+		val &= ~IXP4XX_GPCLK_CLK0_MASK;
+		val |= (0 << IXP4XX_GPCLK_CLK0DC_SHIFT);
+		val |= (1 << IXP4XX_GPCLK_CLK0TC_SHIFT);
+		val |= IXP4XX_GPCLK_MUX14;
+	}
+
+	if (of_property_read_bool(np, "intel,ixp4xx-gpio15-clkout")) {
+		val &= ~IXP4XX_GPCLK_CLK1_MASK;
+		val |= (0 << IXP4XX_GPCLK_CLK1DC_SHIFT);
+		val |= (1 << IXP4XX_GPCLK_CLK1TC_SHIFT);
+		val |= IXP4XX_GPCLK_MUX15;
+	}
+	__raw_writel(val, g->base + IXP4XX_REG_GPCLK);
 
 	/*
 	 * This is a very special big-endian ARM issue: when the IXP4xx is

-- 
2.41.0