The use of gpio by Qualcomm msm8909@ TOC

1. Many nodes are defined in the file msm8909-pinctrl.dtsi to set the function of pin combination, for example:

pmx_i2c_5 {	//The name can be used casually without practical effect
			i2c_5_active: i2c_5_active {	//I2C ﹣ 5 ﹣ active is the alias of this child node, which will be used when it is referenced elsewhere
				mux {
					pins = "gpio19", "gpio18";
					function = "blsp_i2c5";		//Define the reuse function of the above two pins
				};
				config {								//Set the basic characteristics of pin pin pin, such as output current, pull-up / pull-down / no pull-up
					pins = "gpio19", "gpio18";
					drive-strength = <2>; /* 2 MA */
					bias-disable; /* No PULL */
				};
			};
			i2c_5_sleep: i2c_5_sleep {
				mux {
					pins = "gpio19", "gpio18";
					function = "blsp_i2c5";
				};
				config {
					pins = "gpio19", "gpio18";
					drive-strength = <2>; /* 2 MA */
					bias-disable; /* No PULL */
				};
			};
		};

1. If we want to use gpio20, gpio21, gpio22 as general GPIO output.
   2.1 first of all, we need to set its multiplexing function in our project dtsi (msm8909-pinctrl.dtsi as a public file, try not to modify it), such as the following definition in msm8909-mtp.dtsi:
   Node framework of msm8909-pinctrl.dtsi:

&soc {
	**msm_gpio**: pinctrl@1000000 {
		compatible = "qcom,msm8909-pinctrl";
		reg = <0x1000000 0x300000>;
		interrupts = <0 208 0>;
		gpio-controller;
		#gpio-cells = <2>;
		interrupt-controller;
		#interrupt-cells = <2>;
		........
		tlmm_gpio_key {
			gpio_key_active: gpio_key_active {
				mux {
					pins = "gpio90", "gpio91", "gpio92", "gpio22";
					function = "gpio";
				};

				config {
					pins = "gpio90", "gpio91", "gpio92", "gpio22";
					drive-strength = <2>;
					bias-pull-up;
				};
			};
		};
		......
	};
};

&**msm_gpio** {	//This is a reference to the msm8909-pinctrl.dtsi node
	cup_gpios {		//Join the node you want to use
		cup_led_gpios: cup_led_gpios {	//The alias will be referenced by other nodes to
			mux {
				pins = "gpio20", "gpio21", "gpio22";
				function = "gpio";
			};

			config {
				pins = "gpio20", "gpio21", "gpio22";
				drive-strength = <2>;   /* 2 MA */
				bias-pull-down;	        /* PULL DOWN */
			};
		};
	};

};

2.2 reference to user-defined nodes in 2.1
We also define the nodes in msm8909-mtp.dtsi to match the platform driver driver, as follows:

	cup-leds {
		compatible = "cup-leds";
		pinctrl-names = "jeejio_cup_led_gpios";		//This name is used by the pinctrl? Lookup? State function in the driver
		pinctrl-0 = <&cup_led_gpios>;						//By referring to the nodes defined in 2.1, pinctrl-0 corresponds to the first pinctrl names above. Pinctrl names can be composed of multiple strings, separated by commas.
		gpios = <&msm_gpio 22 0x1>,	/* R */       //Define a gpio sequence
				<&msm_gpio 21 0x1>,	/* G */
				<&msm_gpio 20 0x1>;	/* B */
	};

2.3 use of gpio in drivers

	/* Get pinctrl if target uses pinctrl */
	cup_pinctrl = devm_pinctrl_get(&pdev->dev);		//Get the pinctrl handle
	if (IS_ERR(cup_pinctrl)) {
		if (PTR_ERR(cup_pinctrl) == -EPROBE_DEFER)
			return -EPROBE_DEFER;

		pr_debug("Jeejio cup does not use pinctrl\n");
		cup_pinctrl = NULL;
	}

	set_state = pinctrl_lookup_state(cup_pinctrl, "jeejio_cup_led_gpios");	//Get cup led gpios
	if (IS_ERR(set_state)) {
		pr_err(	"cannot get jeejio cup pinctrl active state\n");
		return PTR_ERR(set_state);
	}

	ret = pinctrl_select_state(cup_pinctrl, set_state);	//Set each gpio in cup led gpios
	if (ret) {
		pr_err(	"cannot set jeejio cup pinctrl active state\n");
		return ret;
	}

	for(i = 0; i < GPIO_NUM; i++)
	{
		cup_gpio[i] = of_get_gpio(pdev->dev.of_node, i);	//3 gpios defined by gpio sequence in 2.2, with index: 0, 1, 2
		ret = gpio_request(cup_gpio[i], "rgb_gpio");
		if(ret)
		{
			pr_err("request gpio err!\n");
		}
		else
		{
			pr_err("request gpio success!\n");
		}

		ret = gpio_direction_output(cup_gpio[i], 1);
		if(ret)
		{
			pr_err("set gpio direction err!\n");
		}
		else
		{
			pr_err("set gpio direction success!\n");
		}
	}