lradc按键驱动程序分析（for F1C100S）

柔光的暖阳◎ 2021-07-26 12:06 785阅读 0赞

**设备树dts文件**  
arch/arm/boot/dts/suniv.dtsi 添加:

lradc: lradc@1c23400 { 
            compatible = "allwinner,sun4i-a10-lradc-keys";
            reg = <0x01c23400 0x400>;
            interrupts = <22>;
            status = "disabled";
    };
    
    
    &lradc { 
            vref-supply = <&reg_vcc3v3>;
            status = "okay";
    
            button@200 { 
                    label = "Volume Up";
                    linux,code = <132>;
                    channel = <0>;
                    voltage = <200000>;
            };
    
            button@400 { 
                    label = "Volume Down";
                    linux,code = <133>;
                    channel = <0>;
                    voltage = <400000>;
            };
    
            button@600 { 
                    label = "Select";
                    linux,code = <134>;
                    channel = <0>;
                    voltage = <600000>;
            };
    
            button@800 { 
                    label = "Start";
                    linux,code = <135>;
                    channel = <0>;
                    voltage = <800000>;
            };
    };

编译生成设备树：

make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- dtbs -j4

**驱动源码**

#include <linux/err.h>
    #include <linux/init.h>
    #include <linux/input.h>
    #include <linux/interrupt.h>
    #include <linux/io.h>
    #include <linux/module.h>
    #include <linux/of_platform.h>
    #include <linux/platform_device.h>
    #include <linux/regulator/consumer.h>
    #include <linux/slab.h>
    
    #define LRADC_CTRL 0x00
    #define LRADC_INTC 0x04
    #define LRADC_INTS 0x08
    #define LRADC_DATA0 0x0c
    #define LRADC_DATA1 0x10
    
    /* LRADC_CTRL bits */
    #define FIRST_CONVERT_DLY(x) ((x) << 24) /* 8 bits */
    #define CHAN_SELECT(x) ((x) << 22) /* 2 bits */
    #define CONTINUE_TIME_SEL(x) ((x) << 16) /* 4 bits */
    #define KEY_MODE_SEL(x) ((x) << 12) /* 2 bits */
    #define LEVELA_B_CNT(x) ((x) << 8) /* 4 bits */
    #define HOLD_KEY_EN(x) ((x) << 7)
    #define HOLD_EN(x) ((x) << 6)
    #define LEVELB_VOL(x) ((x) << 4) /* 2 bits */
    #define SAMPLE_RATE(x) ((x) << 2) /* 2 bits */
    #define ENABLE(x) ((x) << 0)
    
    /* LRADC_INTC and LRADC_INTS bits */
    #define CHAN1_KEYUP_IRQ BIT(12)
    #define CHAN1_ALRDY_HOLD_IRQ BIT(11)
    #define CHAN1_HOLD_IRQ BIT(10)
    #define CHAN1_KEYDOWN_IRQ BIT(9)
    #define CHAN1_DATA_IRQ BIT(8)
    #define CHAN0_KEYUP_IRQ BIT(4)
    #define CHAN0_ALRDY_HOLD_IRQ BIT(3)
    #define CHAN0_HOLD_IRQ BIT(2)
    #define CHAN0_KEYDOWN_IRQ BIT(1)
    #define CHAN0_DATA_IRQ BIT(0)
    
    /* struct lradc_variant - Describe sun4i-a10-lradc-keys hardware variant * @divisor_numerator: The numerator of lradc Vref internally divisor * @divisor_denominator: The denominator of lradc Vref internally divisor */
    struct lradc_variant { 
    	u8 divisor_numerator;
    	u8 divisor_denominator;
    };
    
    static const struct lradc_variant lradc_variant_a10 = { 
    	.divisor_numerator = 2,
    	.divisor_denominator = 3
    };
    
    static const struct lradc_variant r_lradc_variant_a83t = { 
    	.divisor_numerator = 3,
    	.divisor_denominator = 4
    };
    
    struct sun4i_lradc_keymap { 
    	u32 voltage;
    	u32 keycode;
    };
    /*sun4i_lradc_data结构体*/
    struct sun4i_lradc_data { 
    	struct device *dev;
    	struct input_dev *input;
    	void __iomem *base;
    	struct regulator *vref_supply;
    	struct sun4i_lradc_keymap *chan0_map;
    	const struct lradc_variant *variant;
    	u32 chan0_map_count;
    	u32 chan0_keycode;
    	u32 vref;
    };
    /*lradc中断*/
    static irqreturn_t sun4i_lradc_irq(int irq, void *dev_id)
    { 
    	struct sun4i_lradc_data *lradc = dev_id;
    	u32 i, ints, val, voltage, diff, keycode = 0, closest = 0xffffffff;
    
    	ints  = readl(lradc->base + LRADC_INTS);  //读取中断类型
    
    	/* * lradc supports only one keypress at a time, release does not give * any info as to which key was released, so we cache the keycode. */
    //中断类型为按键释放
    	if (ints & CHAN0_KEYUP_IRQ) { 
    		input_report_key(lradc->input, lradc->chan0_keycode, 0); /*向输入子系统报告产生按键事件*/
    		lradc->chan0_keycode = 0;  //按键编码置零
    	}
    //中断类型为按键按下，并且当前按键编码为0
    	if ((ints & CHAN0_KEYDOWN_IRQ) && lradc->chan0_keycode == 0) { 
    		val = readl(lradc->base + LRADC_DATA0) & 0x3f;  //读取adc值
    		voltage = val * lradc->vref / 63;  //计算电压值（vref/63 是电压分辨率，采样位数6bit）
    //根据电压，匹配按键值
    		for (i = 0; i < lradc->chan0_map_count; i++) { 
    			diff = abs(lradc->chan0_map[i].voltage - voltage);
    			//匹配电压差值最小的键值
    			if (diff < closest) { 
    				closest = diff;
    				keycode = lradc->chan0_map[i].keycode;  //确定当前按下的键值
    			}
    		}
    
    		lradc->chan0_keycode = keycode;
    		input_report_key(lradc->input, lradc->chan0_keycode, 1);  /*向输入子系统报告产生按键事件*/
    	}
    
    	input_sync(lradc->input);   /*通知接收者,一个报告发送完毕*/
    
    	writel(ints, lradc->base + LRADC_INTS); //写回寄存器（还未查阅芯片手册，应该是清除中断吧）
    
    	return IRQ_HANDLED;
    }
    
    
    static int sun4i_lradc_open(struct input_dev *dev)
    { 
    	struct sun4i_lradc_data *lradc = input_get_drvdata(dev); /* 从设备的私有数据区获取设备描述结构体，可通过nput_set_drvdata 保存数据*/
    	int error;
    	/*regulator 是驱动中电源管理的基础设施。要先注册到内核中，然后使用这些电压输出的模块get其regulator,在驱动中的init里，在适当时间中进行电压电流的设置. 与 gpio 差不多？　一样是基础设施？ 一种称为校准器（regulator）的动态电压和电流控制的方法，很有参考意义和实际使用价值。 */
    
    	error = regulator_enable(lradc->vref_supply);  //打开校准器
    	if (error)
    		return error;
    	
    //通过此接口获取当前电源电压。
    	lradc->vref = regulator_get_voltage(lradc->vref_supply) *
    		      lradc->variant->divisor_numerator /
    		      lradc->variant->divisor_denominator;
    
    	 /**配置LRADC_INTC寄存器，设定采样时间为4ms / 250hz。等待2 * 4 ms的key to *稳定按下，等待(1 + 1)* 4毫秒后释放按键 */
    	writel(FIRST_CONVERT_DLY(2) | LEVELA_B_CNT(1) | HOLD_EN(1) |
    		SAMPLE_RATE(0) | ENABLE(1), lradc->base + LRADC_CTRL);
    
    	writel(CHAN0_KEYUP_IRQ | CHAN0_KEYDOWN_IRQ, lradc->base + LRADC_INTC);
    
    	return 0;
    }
    
    static void sun4i_lradc_close(struct input_dev *dev)
    { 
    	struct sun4i_lradc_data *lradc = input_get_drvdata(dev);
    
    	/* Disable lradc, leave other settings unchanged */
    	writel(FIRST_CONVERT_DLY(2) | LEVELA_B_CNT(1) | HOLD_EN(1) |
    		SAMPLE_RATE(2), lradc->base + LRADC_CTRL);
    	writel(0, lradc->base + LRADC_INTC);
    
    	regulator_disable(lradc->vref_supply);
    }
    //加载设备树资源
    static int sun4i_lradc_load_dt_keymap(struct device *dev,
    				      struct sun4i_lradc_data *lradc)
    { 
    	struct device_node *np, *pp;
    	int i;
    	int error;
    
    	np = dev->of_node;
    	if (!np)
    		return -EINVAL;
    
    	lradc->chan0_map_count = of_get_child_count(np);
    	if (lradc->chan0_map_count == 0) { 
    		dev_err(dev, "keymap is missing in device tree\n");
    		return -EINVAL;
    	}
    
    	lradc->chan0_map = devm_kmalloc_array(dev, lradc->chan0_map_count,
    					      sizeof(struct sun4i_lradc_keymap),
    					      GFP_KERNEL);
    	if (!lradc->chan0_map)
    		return -ENOMEM;
    
    	i = 0;
    	for_each_child_of_node(np, pp) { 
    		struct sun4i_lradc_keymap *map = &lradc->chan0_map[i];
    		u32 channel;
    
    		error = of_property_read_u32(pp, "channel", &channel);
    		if (error || channel != 0) { 
    			dev_err(dev, "%pOFn: Inval channel prop\n", pp);
    			return -EINVAL;
    		}
    
    		error = of_property_read_u32(pp, "voltage", &map->voltage);
    		if (error) { 
    			dev_err(dev, "%pOFn: Inval voltage prop\n", pp);
    			return -EINVAL;
    		}
    
    		error = of_property_read_u32(pp, "linux,code", &map->keycode);
    		if (error) { 
    			dev_err(dev, "%pOFn: Inval linux,code prop\n", pp);
    			return -EINVAL;
    		}
    
    		i++;
    	}
    
    	return 0;
    }
    
    static int sun4i_lradc_probe(struct platform_device *pdev)
    { 
    	struct sun4i_lradc_data *lradc;
    	struct device *dev = &pdev->dev;
    	int i;
    	int error;
    
    	lradc = devm_kzalloc(dev, sizeof(struct sun4i_lradc_data), GFP_KERNEL);
    	if (!lradc)
    		return -ENOMEM;
    
    	error = sun4i_lradc_load_dt_keymap(dev, lradc);
    	if (error)
    		return error;
    
    	lradc->variant = of_device_get_match_data(&pdev->dev);
    	if (!lradc->variant) { 
    		dev_err(&pdev->dev, "Missing sun4i-a10-lradc-keys variant\n");
    		return -EINVAL;
    	}
    
    	lradc->vref_supply = devm_regulator_get(dev, "vref");
    	if (IS_ERR(lradc->vref_supply))
    		return PTR_ERR(lradc->vref_supply);
    
    	lradc->dev = dev;
    	lradc->input = devm_input_allocate_device(dev);
    	if (!lradc->input)
    		return -ENOMEM;
    
    	lradc->input->name = pdev->name;
    	lradc->input->phys = "sun4i_lradc/input0";
    	lradc->input->open = sun4i_lradc_open;
    	lradc->input->close = sun4i_lradc_close;
    	lradc->input->id.bustype = BUS_HOST;
    	lradc->input->id.vendor = 0x0001;
    	lradc->input->id.product = 0x0001;
    	lradc->input->id.version = 0x0100;
    
    	__set_bit(EV_KEY, lradc->input->evbit);
    	for (i = 0; i < lradc->chan0_map_count; i++)
    		__set_bit(lradc->chan0_map[i].keycode, lradc->input->keybit);
    
    	input_set_drvdata(lradc->input, lradc);
    
    	lradc->base = devm_ioremap_resource(dev,
    			      platform_get_resource(pdev, IORESOURCE_MEM, 0));
    	if (IS_ERR(lradc->base))
    		return PTR_ERR(lradc->base);
    
    	error = devm_request_irq(dev, platform_get_irq(pdev, 0),
    				 sun4i_lradc_irq, 0,
    				 "sun4i-a10-lradc-keys", lradc);
    	if (error)
    		return error;
    
    	error = input_register_device(lradc->input);
    	if (error)
    		return error;
    
    	return 0;
    }
    
    static const struct of_device_id sun4i_lradc_of_match[] = { 
    	{  .compatible = "allwinner,sun4i-a10-lradc-keys",
    		.data = &lradc_variant_a10 },
    	{  .compatible = "allwinner,sun8i-a83t-r-lradc",
    		.data = &r_lradc_variant_a83t },
    	{  /* sentinel */ }
    };
    MODULE_DEVICE_TABLE(of, sun4i_lradc_of_match);
    
    static struct platform_driver sun4i_lradc_driver = { 
    	.driver = { 
    		.name	= "sun4i-a10-lradc-keys",
    		.of_match_table = of_match_ptr(sun4i_lradc_of_match),
    	},
    	.probe	= sun4i_lradc_probe,
    };
    
    module_platform_driver(sun4i_lradc_driver);
    
    MODULE_DESCRIPTION("Allwinner sun4i low res adc attached tablet keys driver");
    MODULE_AUTHOR("Hans de Goede <hdegoede@redhat.com>");

**按键输入测试代码**

#include <sys/types.h>
    #include <sys/stat.h>
    #include <fcntl.h>
    #include <stdio.h>
    #include <poll.h>
    #include <signal.h>
    #include <sys/types.h>
    #include <unistd.h>
    #include <fcntl.h>
    
    #include <linux/input.h>
    
    
    
    int fd;
    
    void my_signal_fun(int signum)
    { 
        struct input_event buttons_event, leds_event;
    
        /* [cgw]: 异步通知产生时返回的数据 */
        read(fd, &buttons_event, sizeof(struct input_event));
    
        /* [cgw]: 打印事件类型，事件码，事件值 */
        printf("type: 0x%x code: 0x%x value: 0x%x\n", 
               buttons_event.type,
               buttons_event.code,  
               buttons_event.value);
    
        // /* [cgw]: 返回的是KEY_L或KEY_S值 */
        // if (buttons_event.code == KEY_L || buttons_event.code == KEY_S) { 
        // /* [cgw]: 按键弹起 */ 
        // if (buttons_event.value == 0) { 
    
        // /* [cgw]: 构造一个EV_LED事件 */
                
        // //leds_event.type = EV_SND;
        // leds_event.type = EV_LED;
        // //leds_event.code = SND_BELL;
        // leds_event.code = LED_MUTE;
    
        // /* [cgw]: KEY_L和KEY_S控制LED的亮灭 */
        // if (buttons_event.code == KEY_L) { 
        // leds_event.value = 0xAA;
        // } else if (buttons_event.code == KEY_S) { 
        // leds_event.value = 0xEE; 
        // }
    
        // /* [cgw]: 发送LED控制事件 */
        // write(fd, &leds_event, sizeof(struct input_event));
                
        // printf("led write!\n");
        // }
        // }
    
    
    }
    
    int main(int argc, char **argv)
    { 
        int Oflags;
    
        /* [cgw]: 设置需要处理的信号SIGIO，即输入文件会请求一个SIGIO * 信号，当有新数据到来这个信号会发给filp->f_owner进程 */
        signal(SIGIO, my_signal_fun);
        
        fd = open("/dev/input/event0", O_RDWR | O_NONBLOCK);
        
        //printf("fd = 0x%x\n", fd);
        
        if (fd < 0)
        { 
            printf("can't open!\n");
        }
    
        /* [cgw]: 根据文件标识符fd，设置能够获得这个文件的进程(owner) * getpid()获得当前进程ID */
        fcntl(fd, F_SETOWN, getpid());
    
        /* [cgw]: 获得file->f_flags标志 */
        Oflags = fcntl(fd, F_GETFL); 
        
        /* [cgw]: 置位FASYNC使能异步通知 */
        fcntl(fd, F_SETFL, Oflags | FASYNC);
    
        while (1)
        { 
            /* [cgw]: 休眠 */
            sleep(1000);
        }
        
        return 0;
    }