iio: adc: Add dt support for turning on the phy in exynos-adc

Without this change the exynos adc controller needed to have its phy
enabled in some out-of-driver C code. Add support for specifying the
phy enable register by listing it in the reg list.

Signed-off-by: Doug Anderson <[e-mail]>
Tested-by: Naveen Krishna Chatradhi <[e-mail]>
Signed-off-by: Jonathan Cameron <[e-mail]>

Documentation/devicetree/bindings/arm/samsung/exynos-adc.txt

···
 			Must be "samsung,exynos-adc-v2" for
 				future controllers.
 - reg:			Contains ADC register address range (base address and
-			length).
+			length) and the address of the phy enable register.
 - interrupts: 		Contains the interrupt information for the timer. The
 			format is being dependent on which interrupt controller
 			the Samsung device uses.
···
 
 adc: adc@12D10000 {
 	compatible = "samsung,exynos-adc-v1";
-	reg = <0x12D10000 0x100>;
+	reg = <0x12D10000 0x100>, <0x10040718 0x4>;
 	interrupts = <0 106 0>;
 	#io-channel-cells = <1>;
 	io-channel-ranges;

drivers/iio/adc/exynos_adc.c

···
 
 struct exynos_adc {
 	void __iomem		*regs;
+	void __iomem		*enable_reg;
 	struct clk		*clk;
 	unsigned int		irq;
 	struct regulator	*vdd;
···
 	info = iio_priv(indio_dev);
 
 	mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
-
 	info->regs = devm_request_and_ioremap(&pdev->dev, mem);
 	if (!info->regs) {
+		ret = -ENOMEM;
+		goto err_iio;
+	}
+
+	mem = platform_get_resource(pdev, IORESOURCE_MEM, 1);
+	info->enable_reg = devm_request_and_ioremap(&pdev->dev, mem);
+	if (!info->enable_reg) {
 		ret = -ENOMEM;
 		goto err_iio;
 	}
···
 							info->irq);
 		goto err_iio;
 	}
+
+	writel(1, info->enable_reg);
 
 	info->clk = devm_clk_get(&pdev->dev, "adc");
 	if (IS_ERR(info->clk)) {
···
 				exynos_adc_remove_devices);
 	regulator_disable(info->vdd);
 	clk_disable_unprepare(info->clk);
+	writel(0, info->enable_reg);
 	iio_device_unregister(indio_dev);
 	free_irq(info->irq, info);
 	iio_device_free(indio_dev);
···
 	}
 
 	clk_disable_unprepare(info->clk);
+	writel(0, info->enable_reg);
 	regulator_disable(info->vdd);
 
 	return 0;
···
 	if (ret)
 		return ret;
 
+	writel(1, info->enable_reg);
 	clk_prepare_enable(info->clk);
 
 	exynos_adc_hw_init(info);