linux裝置樹筆記__基於msm8x10的基本分析
由文章,linux裝置樹筆記__dts基本概念及語法,我們知道了基本概念,知道了大概的裝置樹節點及其屬性,而節點下的屬性大多是自定義,除了保留的幾個屬性,大多從.dts是無法知道其用途的,這個就需要看驅動是如何解析屬性值的了,這點也可作技術細節的部分隱藏。
在原始碼的msm8x12\kernel\arch\arm\boot\dts下有很多xxx.dts,xxx.dtsi,一般一個board就有一個.dts,所以你能看見很多dts檔案,即使一個SOC也可能有不同的dts,這樣不同的dts會共用很多的裝置,那麼.dtsi就是起共用裝置樹的作用,一個板子dts可以像C語言一樣來包含dtsi,如/include/ "msm8612-qrd-camera-sensor.dtsi"。
msm8x12\kernel\arch\arm\mach-msm\Makefile.boot關於編譯msm8x12的dts部分。
# MSM8610 zreladdr-$(CONFIG_ARCH_MSM8610) := 0x00008000 dtb-$(CONFIG_ARCH_MSM8610) += msm8610-v1-cdp.dtb dtb-$(CONFIG_ARCH_MSM8610) += msm8610-v2-cdp.dtb dtb-$(CONFIG_ARCH_MSM8610) += msm8610-v1-mtp.dtb dtb-$(CONFIG_ARCH_MSM8610) += msm8610-v2-mtp.dtb dtb-$(CONFIG_ARCH_MSM8610) += msm8610-rumi.dtb dtb-$(CONFIG_ARCH_MSM8610) += msm8610-sim.dtb dtb-$(CONFIG_ARCH_MSM8610) += msm8610-v1-qrd-skuaa.dtb dtb-$(CONFIG_ARCH_MSM8610) += msm8610-v1-qrd-skuab.dtb dtb-$(CONFIG_ARCH_MSM8610) += msm8610-v2-qrd-skuaa.dtb dtb-$(CONFIG_ARCH_MSM8610) += msm8610-v2-qrd-skuab.dtb ifeq ($(CONFIG_ARCH_MSM8610_CB01),y) dtb-$(CONFIG_ARCH_MSM8610) += board-seuic-cb01.dtb endif ifeq ($(CONFIG_ARCH_MSM8610_D330S),y) dtb-$(CONFIG_ARCH_MSM8610) += board-seuic-d330s.dtb endif ifeq ($(CONFIG_ARCH_MSM8610_D500),y) dtb-$(CONFIG_ARCH_MSM8610) += board-seuic-d500.dtb endif ifeq ($(CONFIG_ARCH_MSM8610_D510),y) dtb-$(CONFIG_ARCH_MSM8610) += board-seuic-d510.dtb endif
在msm8x12的SOC我們有3個板子型號,假設我們選擇的是d500的型號,那麼我們一般的不同硬體配置相關都是在board-seuci-d500.dtb中修改,其他的dtb目標檔案都是共有的硬體配置,因為我們都是一樣的SOC嘛。
/ {
model = "Qualcomm MSM 8610v2 QRD SKUAB D510";
compatible = "qcom,msm8610-qrd", "qcom,msm8610", "qcom,qrd";
qcom,board-id = <0x6000b 3>;
};
其中model和compatible每個板子都有,前者是SOC描述,後者是board型號,後者一般用公司名加上soc型號組合,多個值表示相容board,並且不要和其他board重名,qcom,board-id是自定義的,有的板子還有qcom,msm-id。
板子中的裝置節點一般通過compatible來標示查詢的,下面提取board-seuic-d500.dtb的部分裝置進行解析並檢視驅動是如何利用的:
LED裝置:
&soc {
...
gpio-leds {
compatible = "gpio-leds";//驅動要匹配的關鍵字
status = "ok";
/* scan_led */
red1_led {
gpios = <&pm8110_gpios 1 0x0>;
label = "scan";
linux,default-trigger = "heartbeat";
default-state = "off";
};
/* charge_ing */
red2_led {
gpios = <&pm8110_gpios 3 0x0>;
label = "red1";
linux,default-trigger = "battery-charging";
default-state = "off";
retain-state-suspended = "yes";
};
/* charge_complete */
green_led {
gpios = <&pm8110_gpios 2 0x0>;
label = "green1";
linux,default-trigger = "battery-full";
default-state = "off";
retain-state-suspended = "yes";
};
};
...
};
裝置樹中的SOC下一級的裝置gpio-leds,有三個子節點,分別是掃描燈,充電中指示燈,充電完成指示燈,下面以充電完成指示燈來說明。
對應的驅動在msm8x12\kernel\drivers\leds\leds-gpio.c,驅動中使用of相關驅動來解析dts,且全域性巨集為CONFIG_OF_GPIO。
驅動中在probe前要匹配的關鍵字是compatible的值,如下,並且匹配優先順序of_match_table > id_table > driver.name,且不管是id_table還是of_match_table都要以一個空元素結尾。
static const struct of_device_id of_gpio_leds_match[] = {
{ .compatible = "gpio-leds", },
{},
};
static struct platform_driver gpio_led_driver = {
.probe = gpio_led_probe,
.remove = __devexit_p(gpio_led_remove),
.driver = {
.name = "leds-gpio",
.owner = THIS_MODULE,
.of_match_table = of_gpio_leds_match,
},
};
module_platform_driver(gpio_led_driver);
匹配成功後才會呼叫probe,其中module_platform_driver(gpio_led_driver)是一個模組初始化和退出的巨集:
#define module_platform_driver(__platform_driver) \
static int __init __platform_driver##_init(void) \
{ \
return platform_driver_register(&(__platform_driver)); \
} \
module_init(__platform_driver##_init); \
static void __exit __platform_driver##_exit(void) \
{ \
platform_driver_unregister(&(__platform_driver)); \
} \
module_exit(__platform_driver##_exit);
gpio_led_probe->gpio_leds_create_of()函式就是解析上述LED裝置節點的過程:
static struct gpio_leds_priv * __devinit gpio_leds_create_of(struct platform_device *pdev)
{
struct device_node *np = pdev->dev.of_node, *child;
struct gpio_leds_priv *priv;
int count = 0, ret;
/* count LEDs in this device, so we know how much to allocate */
for_each_child_of_node(np, child)
count++;
if (!count)
return NULL;
priv = kzalloc(sizeof_gpio_leds_priv(count), GFP_KERNEL);
if (!priv)
return NULL;
for_each_child_of_node(np, child) {
struct gpio_led led = {};
enum of_gpio_flags flags;
const char *state;
const char *retain_state;
led.gpio = of_get_gpio_flags(child, 0, &flags);//獲取gpio序號及有效標誌,實際上是通過gpios屬性獲取
led.active_low = flags & OF_GPIO_ACTIVE_LOW;//如為OF_GPIO_ACTIVE_LOW即值為1,那麼點亮set 0就是set 1,要進行邏輯取反
led.name = of_get_property(child, "label", NULL) ? : child->name;//label屬性為子節點裝置名
led.default_trigger =//預設的LED trigger
of_get_property(child, "linux,default-trigger", NULL);
state = of_get_property(child, "default-state", NULL);//開機預設的LED狀態
if (state) {
if (!strcmp(state, "keep"))
led.default_state = LEDS_GPIO_DEFSTATE_KEEP;
else if (!strcmp(state, "on"))
led.default_state = LEDS_GPIO_DEFSTATE_ON;
else
led.default_state = LEDS_GPIO_DEFSTATE_OFF;
}
retain_state = of_get_property(child, "retain-state-suspended", NULL);//休眠時LED的狀態
if (retain_state) {
if (!strcmp(retain_state, "yes"))
led.retain_state_suspended = 1;
else
led.retain_state_suspended = 0;
}
ret = create_gpio_led(&led, &priv->leds[priv->num_leds++],//建立LED裝置
&pdev->dev, NULL);
if (ret < 0) {
of_node_put(child);
goto err;
}
}
return priv;
err:
for (count = priv->num_leds - 2; count >= 0; count--)
delete_gpio_led(&priv->leds[count]);
kfree(priv);
return NULL;
}
如驅動中所示,大多通過of_xxx的API函式來解析dts裝置節點屬性,屬性就是KEY-VALUE結構,至於值的意義完全由驅動來控制。比如of_get_property(child, "linux,default-trigger", NULL),其中child是當前裝置節點,引數二就是待查詢的屬性,返回值是對應屬性的值,此處就是對應於DTS的linux,default-trigger = "battery-full",進行解析,返回值應該為“battery-full”,至於這個LED
trigger的意義及用法見我的另一篇文章《linux驅動____LED子系統筆記》。
NOTE:另外需要注意的是,對於屬性名,是否可以隨意定義,要看of的API程式碼,比如gpios屬性名是API裡使用的,用來指示使用的gpio號及有效標誌位,就必須這麼用不能改名;
/**
* of_get_gpio_flags() - Get a GPIO number and flags to use with GPIO API
* @np: device node to get GPIO from
* @index: index of the GPIO
* @flags: a flags pointer to fill in
*
* Returns GPIO number to use with Linux generic GPIO API, or one of the errno
* value on the error condition. If @flags is not NULL the function also fills
* in flags for the GPIO.
*/
static inline int of_get_gpio_flags(struct device_node *np, int index,
enum of_gpio_flags *flags)
{
return of_get_named_gpio_flags(np, "gpios", index, flags);
}
而對於像"linux,default-trigger"是可以隨便定義的,因為它唯一使用的地方就是使用of相關API在驅動中獲取屬性值,完全由驅動開發者的思維邏輯控制的。
觸屏:下面再舉1個觸屏的例子,同一個I2C匯流排掛了多個裝置,DTS程式碼只貼出2個:
&soc {
...
[email protected]{
/*synaptics v2.3 DS4/DS5*/
[email protected] {//節點一般以裝置名@addr組合
compatible = "synaptics,dsx";//觸屏裝置名
reg = <0x20>;//從裝置I2C地址
interrupt-parent = <&msmgpio>;//I2C的中斷給誰處理
interrupts = <1 0x2002>;//I2C中斷給msmgpio處理,後面詳細解釋
vdd-supply = <&pm8110_l19>;//I2C裝置的VDD由電源管理晶片pm8110的pin_114供電
vcc_i2c-supply = <&pm8110_l14>;//與上類似
synaptics,pwr-reg-name = "vdd";//供電名
synaptics,bus-reg-name = "vcc_i2c";//與上類似
synaptics,irq-gpio = <&msmgpio 1 0x2008>;//具體中斷資源連那個gpio
synaptics,irq-flags = <0x2002>;/* IRQF_ONESHOT | IRQF_TRIGGER_FALLING */
synaptics,power-delay-ms = <160>;
synaptics,reset-delay-ms = <100>;
synaptics,swap-axes;
//synaptics,x-flip;
synaptics,y-flip;
synaptics,irq-on-state = <0>;
};
[email protected] {
compatible = "qcom,nfc-akm09911";//電子羅盤裝置名
reg = <0x0d>;//I2C從地址
vdd-supply = <&pm8110_l19>;
vio-supply = <&pm8110_l14>;
akm09911,layout = <3>; //廠商定製的晶片貼片時的佈局標誌
akm09911,reset-pin = <35>;
};
}
...
}
驅動解析在msm8x12\kernel\drivers\input\touchscreen\synaptics_dsx\synaptics_dsx_i2c.c
dts裝置匹配驅動,我們的DTS中compatible = "synaptics,dsx"與of_match_table是中的值是一致的,匹配成功!
#ifdef CONFIG_OF
static struct of_device_id synaptics_rmi4_of_match_table[] = {
{
.compatible = "synaptics,dsx",
},
{},
};
MODULE_DEVICE_TABLE(of, synaptics_rmi4_of_match_table);
#else
#define synaptics_rmi4_of_match_table NULL
#endif
static const struct i2c_device_id synaptics_rmi4_id_table[] = {
{"synaptics_dsx_i2c", 0},
{},
};
MODULE_DEVICE_TABLE(i2c, synaptics_rmi4_id_table);
static struct i2c_driver synaptics_rmi4_i2c_driver = {
.driver = {
.name = I2C_DRIVER_NAME,
.owner = THIS_MODULE,
.of_match_table = synaptics_rmi4_of_match_table,
},
.probe = synaptics_rmi4_i2c_probe,
.remove = __devexit_p(synaptics_rmi4_i2c_remove),
.id_table = synaptics_rmi4_id_table,
};
在synaptics_rmi4_i2c_probe()->parse_dt()中,
static int parse_dt(struct device *dev, struct synaptics_dsx_board_data *bdata)
{
int retval;
u32 value;
const char *name;
struct property *prop;
struct device_node *np = dev->of_node;
bdata->irq_gpio = of_get_named_gpio_flags(np,//中斷gpio號,忽略flag
"synaptics,irq-gpio", 0, NULL);
retval = of_property_read_u32(np, "synaptics,irq-on-state",//中斷處理時gpio電平是H還是L
&value);
if (retval < 0)
bdata->irq_on_state = 0;
else
bdata->irq_on_state = value;
retval = of_property_read_u32(np, "synaptics,irq-flags", &value);//中斷觸發處理標誌
if (retval < 0)
return retval;
else
bdata->irq_flags = value;
retval = of_property_read_string(np, "synaptics,pwr-reg-name", &name);//供電名,作為後面regulator_get的引數id
if (retval == -EINVAL)
bdata->pwr_reg_name = NULL;
else if (retval < 0)
return retval;
else
bdata->pwr_reg_name = name;
retval = of_property_read_string(np, "synaptics,bus-reg-name", &name);//同上
if (retval == -EINVAL)
bdata->bus_reg_name = NULL;
else if (retval < 0)
return retval;
else
bdata->bus_reg_name = name;
if (of_property_read_bool(np, "synaptics,power-gpio")) {//DTS未使用到。上電時,power_gpio初始狀態
bdata->power_gpio = of_get_named_gpio_flags(np,
"synaptics,power-gpio", 0, NULL);
retval = of_property_read_u32(np, "synaptics,power-on-state",
&value);
if (retval < 0)
return retval;
else
bdata->power_on_state = value;
} else {
bdata->power_gpio = -1;
}
if (of_property_read_bool(np, "synaptics,power-delay-ms")) {//電源上電或resume時要等待的時間
retval = of_property_read_u32(np, "synaptics,power-delay-ms",
&value);
if (retval < 0)
return retval;
else
bdata->power_delay_ms = value;
} else {
bdata->power_delay_ms = 0;
}
if (of_property_read_bool(np, "synaptics,reset-gpio")) {//DTS未使用
bdata->reset_gpio = of_get_named_gpio_flags(np,
"synaptics,reset-gpio", 0, NULL);
retval = of_property_read_u32(np, "synaptics,reset-on-state",
&value);
if (retval < 0)
return retval;
else
bdata->reset_on_state = value;
retval = of_property_read_u32(np, "synaptics,reset-active-ms",
&value);
if (retval < 0)
return retval;
else
bdata->reset_active_ms = value;
} else {
bdata->reset_gpio = -1;
}
if (of_property_read_bool(np, "synaptics,reset-delay-ms")) {//執行soft-reset時的等待時間
retval = of_property_read_u32(np, "synaptics,reset-delay-ms",
&value);
if (retval < 0)
return retval;
else
bdata->reset_delay_ms = value;
} else {
bdata->reset_delay_ms = 0;
}
if (of_property_read_bool(np, "synaptics,max-y-for-2d")) {//DTS未使用,觸屏報點的Y方向最大值
retval = of_property_read_u32(np, "synaptics,max-y-for-2d",
&value);
if (retval < 0)
return retval;
else
bdata->max_y_for_2d = value;
} else {
bdata->max_y_for_2d = -1;
}
bdata->swap_axes = of_property_read_bool(np, "synaptics,swap-axes");//觸屏報點X,Y交換
bdata->x_flip = of_property_read_bool(np, "synaptics,x-flip");//X值變為關於X中軸對稱
bdata->y_flip = of_property_read_bool(np, "synaptics,y-flip");//Y值變為關於Y中軸對稱
prop = of_find_property(np, "synaptics,cap-button-codes", NULL);//DTS未使用
if (prop && prop->length) {
bdata->cap_button_map->map = devm_kzalloc(dev,
prop->length,
GFP_KERNEL);
if (!bdata->cap_button_map->map)
return -ENOMEM;
bdata->cap_button_map->nbuttons = prop->length / sizeof(u32);
retval = of_property_read_u32_array(np,
"synaptics,cap-button-codes",
bdata->cap_button_map->map,
bdata->cap_button_map->nbuttons);
if (retval < 0) {
bdata->cap_button_map->nbuttons = 0;
bdata->cap_button_map->map = NULL;
}
} else {
bdata->cap_button_map->nbuttons = 0;
bdata->cap_button_map->map = NULL;
}
prop = of_find_property(np, "synaptics,vir-button-codes", NULL);//DTS未使用
if (prop && prop->length) {
bdata->vir_button_map->map = devm_kzalloc(dev,
prop->length,
GFP_KERNEL);
if (!bdata->vir_button_map->map)
return -ENOMEM;
bdata->vir_button_map->nbuttons = prop->length / sizeof(u32);
bdata->vir_button_map->nbuttons /= 5;
retval = of_property_read_u32_array(np,
"synaptics,vir-button-codes",
bdata->vir_button_map->map,
bdata->vir_button_map->nbuttons * 5);
if (retval < 0) {
bdata->vir_button_map->nbuttons = 0;
bdata->vir_button_map->map = NULL;
}
} else {
bdata->vir_button_map->nbuttons = 0;
bdata->vir_button_map->map = NULL;
}
return 0;
}
of_get_named_gpio_flags(np, "synaptics,irq-gpio", 0, NULL)從DTS中獲取中斷gpio即觸屏的中斷連線到soc哪個GPIO上,然後呼叫request_threaded_irq申請中斷及處理函式。
of_property_read_u32(np, "synaptics,irq-on-state", &value),中斷中使用:
static irqreturn_t synaptics_rmi4_irq(int irq, void *data)
{
struct synaptics_rmi4_data *rmi4_data = data;
const struct synaptics_dsx_board_data *bdata =
rmi4_data->hw_if->board_data;
if (gpio_get_value(bdata->irq_gpio) != bdata->irq_on_state)//當前中斷線gpio值與irq_on_state值一致才會報點
goto exit;
synaptics_rmi4_sensor_report(rmi4_data);
exit:
return IRQ_HANDLED;
}
of_property_read_u32(np, "synaptics,irq-flags", &value)是request_threaded_irq()申請中斷處理資源的中斷方式標誌,對應於DTS中的synaptics,irq-flags = <0x2002>,那麼這個值是什麼意思,就是使用標準的中斷方式定義,在msm8x12\kernel\include\linux\interrupt.h中有定義:
//hardware interrupt line behaviour flags
#define IRQF_TRIGGER_NONE 0x00000000
#define IRQF_TRIGGER_RISING 0x00000001
#define IRQF_TRIGGER_FALLING 0x00000002
#define IRQF_TRIGGER_HIGH 0x00000004
#define IRQF_TRIGGER_LOW 0x00000008
#define IRQF_TRIGGER_MASK (IRQF_TRIGGER_HIGH | IRQF_TRIGGER_LOW | \
IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING)
#define IRQF_TRIGGER_PROBE 0x00000010
//used only by the kernel as part of the irq handling routines.
#define IRQF_DISABLED 0x00000020
#define IRQF_SAMPLE_RANDOM 0x00000040
#define IRQF_SHARED 0x00000080
#define IRQF_PROBE_SHARED 0x00000100
#define __IRQF_TIMER 0x00000200
#define IRQF_PERCPU 0x00000400
#define IRQF_NOBALANCING 0x00000800
#define IRQF_IRQPOLL 0x00001000
#define IRQF_ONESHOT 0x00002000
#define IRQF_NO_SUSPEND 0x00004000
#define IRQF_FORCE_RESUME 0x00008000
#define IRQF_NO_THREAD 0x00010000
#define IRQF_EARLY_RESUME 0x00020000
#define IRQF_TIMER (__IRQF_TIMER | IRQF_NO_SUSPEND | IRQF_NO_THREAD)
中斷標誌定義都是掩碼,基本常用的就是上下降沿、高低電平,還有常用的IRQF_DISABLED進行或組合。上述DTS的中斷標誌0x2002就是IRQF_ONESHOT | IRQF_TRIGGER_FALLING,即下降沿觸發中斷,且在中斷thread未完成前不開放中斷。
of_property_read_string(np, "synaptics,pwr-reg-name", &name)對應於DTS的synaptics,pwr-reg-name = "vdd",實際上是regulator的id,根據這個"vdd"的id,可查詢到系統中的vdd-supply,然後控制供電行為的enable和disable。那麼此處是如何做的呢?!
synaptics_rmi4_probe()->
synaptics_rmi4_get_reg()->
regulator_get(rmi4_data->pdev->dev.parent,bdata->pwr_reg_name)->
_regulator_get->
regulator_dev_lookup->
of_get_regulator->
regnode = of_parse_phandle(dev->of_node, prop_name, 0)
最後一個函式使用snprintf(prop_name, 32, "%s-supply", supply),也就是說返回的regnode是對應於id為“vdd-supply”的裝置節點;說到底對於struct regulator *regulator_get(struct device *dev, const char *id),他對於dts的處理就是查詢id為"$(id)-supply"對應的dts屬性值指向的regulator並返回(此處對應於DTS的vdd-supply = <&pm8110_l19>,就是查詢pm8110_119所引用的regulator並返回),這樣驅動就能去控制供電行為了。這樣在觸屏suspend()和resume()是去對應呼叫regulator_disable()和regulator_enable()進行供電的關和開。
其他DTS屬性大多是這樣用的。