OpenRisc-20-or1200下linux的i2c(二)
2013-12-09 10:27
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这段时间开始有点小忙了，但是还是坚持学习一下linux，至于上次记得是基于linux系统自带的i2c-ocores.c文件接口写了简单的测试程序，这次就基于opencores社区上大虾写好的i2c controller总线驱动来做一下分析，这个总线驱动在openrisc-3.1\drivers\i2c\busses目录下~这个总线驱动是基于Richard Herveille编写的i2c-master的ipcore，在opencores社区上可以下到这份RTL的代码，然后打开源码里面的i2c_specs说明文档看看这个ipcores的相关操作。
openrisc-3.1\drivers\i2c\busses\i2c-ocores.c，好~Open之，
然后回想一下之前blog里面写过的关于gpio字符驱动的内容，最后一步我们是把gpio的字符驱动封装成platform机制的，所以，照板煮碗，把代码拉到最后面就可以看到i2c-ocres.c也是同样的道理。
First，定义一个platform_driver结构。
Second，初始化这个结构，指定其probe、remove等函数，并初始化其中的driver变量。
Third，实现其probe、remove等函数。
以上是platform平台驱动的步骤。
然后说明一下i2c总线驱动负责的工作是：
First，申请i2c总线控制器所用到的硬件资源（IO、中断号、内存等等）。
Second，向内核增加一个i2c_adapter数据结构表示这个总线驱动，并且实现i2c_adapter数据结构中的algo成员（即控制i2c控制器的代码）。
所以总线驱动代码的综合效果就是将上面驱动负责的工作写入platform平台驱动，并注册完成i2c总线驱动。
下面来分析一下~
首先，例化关于i2c的平台驱动，这里编写的是对应i2c的总线驱动，所以在例化i2c总线驱动时的of_match_table列表要对应在DTS设备树文件中i2c的总线控制器的compatible，在module加载入kernel时才会按照名称搜索加载i2c的总线驱动。
DTS设备树i2c描述：
[cpp] view
plaincopyprint?
i2c0: ocores@93000000 {
compatible = "opencores,i2c-ocores";
reg = <0x93000000 0x8>;
interrupts = <5>;
regstep = <1>;
clock-frequency = <40000000>;
#address-cells = <1>;
#size-cells = <0>;
eeprom@54 {
compatible = "at24";
reg = <0x54>;
};
};
总线驱动注册代码：
[cpp] view
plaincopyprint?
static struct of_device_id ocores_i2c_match[] = {
{ .compatible = "opencores,i2c-ocores", },
{},
};
MODULE_DEVICE_TABLE(of, ocores_i2c_match);
/* work with hotplug and coldplug */
MODULE_ALIAS("platform:ocores-i2c");
static struct platform_driver ocores_i2c_driver = {
.probe = ocores_i2c_probe,
.remove = __devexit_p(ocores_i2c_remove),
.suspend = ocores_i2c_suspend,
.resume = ocores_i2c_resume,
.driver = {
.owner = THIS_MODULE,
.name = "ocores-i2c",
.of_match_table = ocores_i2c_match,
},
};
static int __init ocores_i2c_init(void)
{
return platform_driver_register(&ocores_i2c_driver);
}
static void __exit ocores_i2c_exit(void)
{
platform_driver_unregister(&ocores_i2c_driver);
}
module_init(ocores_i2c_init);
module_exit(ocores_i2c_exit);
然后，要实现probe、remove等函数
[cpp] view
plaincopyprint?
static int __devinit ocores_i2c_probe(struct platform_device *pdev)
{
struct ocores_i2c *i2c;
struct ocores_i2c_platform_data *pdata;
struct resource *res, *res2;
int ret;
int i;
//获取DTS文件中的IO资源(地址范围)
res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
if (!res)
return -ENODEV;
//获取DTS文件中的中断号资源
res2 = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
if (!res2)
return -ENODEV;
//申请内存
i2c = devm_kzalloc(&pdev->dev, sizeof(*i2c), GFP_KERNEL);
if (!i2c)
return -ENOMEM;
//检查是否有足够内存
if (!devm_request_mem_region(&pdev->dev, res->start,
resource_size(res), pdev->name)) {
dev_err(&pdev->dev, "Memory region busy\n");
return -EBUSY;
}
//i2c控制器wishbone总线物理地址映射到内核地址空间
i2c->base = devm_ioremap_nocache(&pdev->dev, res->start,
resource_size(res));
if (!i2c->base) {
dev_err(&pdev->dev, "Unable to map registers\n");
return -EIO;
}
//例化一个指针指向platform_device的设备的私有数据域，这个数据从编译DTS文件时获取
pdata = pdev->dev.platform_data;
if (pdata) {
i2c->regstep = pdata->regstep;
i2c->clock_khz = pdata->clock_khz;
} else {
ret = ocores_i2c_of_probe(pdev, i2c);
if (ret)
return ret;
}
//初始化i2c控制器，具体可参考i2c_specs
ocores_init(i2c);
//初始化等待队列，目前我还没明白这个，水平有限
init_waitqueue_head(&i2c->wait);
//申请设备使用的中断号，并注册中断函数
ret = devm_request_irq(&pdev->dev, res2->start, ocores_isr, 0,
pdev->name, i2c);
if (ret) {
dev_err(&pdev->dev, "Cannot claim IRQ\n");
return ret;
}
/* hook up driver to tree */
//将i2c保存到platform_device中dev成员的p成员的driver_data数据域中
platform_set_drvdata(pdev, i2c);
i2c->adap = ocores_adapter;
//将i2c保存到i2c_adapter中dev成员的p成员的driver_data数据域中
i2c_set_adapdata(&i2c->adap, i2c);
i2c->adap.dev.parent = &pdev->dev;
i2c->adap.dev.of_node = pdev->dev.of_node;
/* add i2c adapter to i2c tree */
//增加i2c adapter的数据结构
ret = i2c_add_adapter(&i2c->adap);
if (ret) {
dev_err(&pdev->dev, "Failed to add adapter\n");
return ret;
}
/* add in known devices to the bus */
//如果在DTS文件中有多个共享总线驱动的从设备便会枚举出来
if (pdata) {
for (i = 0; i < pdata->num_devices; i++)
i2c_new_device(&i2c->adap, pdata->devices + i);
}
return 0;
}
[cpp] view
plaincopyprint?
static int __devexit ocores_i2c_remove(struct platform_device* pdev)
{
//将之前保存在platform_device中dev成员的p成员的driver_data数据域中的数据取出
struct ocores_i2c *i2c = platform_get_drvdata(pdev);
/* disable i2c logic */
//无效i2c总线控制器
oc_setreg(i2c, OCI2C_CONTROL, oc_getreg(i2c, OCI2C_CONTROL)
& ~(OCI2C_CTRL_EN|OCI2C_CTRL_IEN));
/* remove adapter & data */
//删除完成注册的i2c_adapter
i2c_del_adapter(&i2c->adap);
//删除platform_device中dev成员的p成员的driver_data
platform_set_drvdata(pdev, NULL);
return 0;
}
至于有关电源管理的suspend和resume暂且忽略，内核配置中暂时不去实现。
这样就注册好平台设备驱动。
接下去就在源码中去结合注释和i2c-specs的文档好好看看通信算法处理函数，这也是我们从新开发总线驱动的时候必须去编写的代码~
首先是定义i2c_adapter和其成员变量的algo算法
[cpp] view
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static u32 ocores_func(struct i2c_adapter *adap)
{
return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
}
//定义一个i2c_algorithm的数据结构，其中实现控制器通信算法master_xfer
//和functionality(master_xfer通信算法支持的协议)
static const struct i2c_algorithm ocores_algorithm = {
.master_xfer = ocores_xfer,
.functionality = ocores_func,
};
//定义一个i2c_adapter，完成总线控制器的描述，并在probe中向内核注册
static struct i2c_adapter ocores_adapter = {
.owner = THIS_MODULE,
.name = "i2c-ocores",
.class = I2C_CLASS_HWMON | I2C_CLASS_SPD,
.algo = &ocores_algorithm,
};
其中由于这个驱动是基于中断架构的收发，结合源码继续往下看。
首先看看在probe中调用的ocores_init()，完成的是总线控制器的初始化
[cpp] view
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//根据i2c-specs文档初始化总线控制器
//对比文档中的寄存器进行操作
static void ocores_init(struct ocores_i2c *i2c)
{
int prescale;
//取出Control register寄存器的值，在i2c-specs中有说明~
u8 ctrl = oc_getreg(i2c, OCI2C_CONTROL);
/* make sure the device is disabled */
//i2c cores禁止中断和无效总线控制器
oc_setreg(i2c, OCI2C_CONTROL, ctrl & ~(OCI2C_CTRL_EN|OCI2C_CTRL_IEN));
//设置i2c总线控制器的通信速率，在i2c-specs文档有计算公式
prescale = (i2c->clock_khz / (5*100)) - 1;
//将速率写入PRERlo和PRERhi寄存器
oc_setreg(i2c, OCI2C_PRELOW, prescale & 0xff);
oc_setreg(i2c, OCI2C_PREHIGH, prescale >> 8);
/* Init the device */
//清除中断标志位，使能总线控制器的中断和使能总线控制器
oc_setreg(i2c, OCI2C_CMD, OCI2C_CMD_IACK);
oc_setreg(i2c, OCI2C_CONTROL, ctrl | OCI2C_CTRL_IEN | OCI2C_CTRL_EN);
}
然后程序调用通信算法时会hold住，在中断中处理数据，然后等待事件集到来，完成通信。
[cpp] view
plaincopyprint?
//发送和接收调用的总线通信算法函数
static int ocores_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
{
//在ocores_i2c中有i2c_adapter成员，而i2c_adapter成员在probe进行时
//已经由i2c_set_adapdata()保存到i2c_adapter中，所以这里取出保存在
//i2c_adapter中dev成员的p成员的driver_data数据域
struct ocores_i2c *i2c = i2c_get_adapdata(adap);
//获取由应用层传入的i2c message
i2c->msg = msgs;
i2c->pos = 0;
i2c->nmsgs = num;
i2c->state = STATE_START;
//根据i2c message类型是读还是写进行器件地址选择和设置LSB的读写位
oc_setreg(i2c, OCI2C_DATA,
(i2c->msg->addr << 1) |
((i2c->msg->flags & I2C_M_RD) ? 1:0));
//根据i2c协议第一次是写器件地址和读写位的组合
oc_setreg(i2c, OCI2C_CMD, OCI2C_CMD_START);
//等待事件集到来，???操作系统没学过，现在恶补
if (wait_event_timeout(i2c->wait, (i2c->state == STATE_ERROR) ||
(i2c->state == STATE_DONE), HZ))
return (i2c->state == STATE_DONE) ? num : -EIO;
else
return -ETIMEDOUT;
}
[cpp] view
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[cpp] view
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//当总线控制器完成一个byte发送和接收时调用的中断函数
//因为这个驱动采用了中断的方式收发数据
static irqreturn_t ocores_isr(int irq, void *dev_id)
{
struct ocores_i2c *i2c = dev_id;
ocores_process(i2c);
return IRQ_HANDLED;
}
[cpp] view
plaincopyprint?
//当总线控制器完成一个byte发送和接收时调用的中断函数
//因为这个驱动采用了中断的方式收发数据
static irqreturn_t ocores_isr(int irq, void *dev_id)
{
struct ocores_i2c *i2c = dev_id;
ocores_process(i2c);
return IRQ_HANDLED;
}
[cpp] view
plaincopyprint?
//中断处理函数的处理过程，目前没认真整理过，根据i2c通信协议再好好看看
//然后有时间再总结出来
static void ocores_process(struct ocores_i2c *i2c)
{
struct i2c_msg *msg = i2c->msg;
u8 stat = oc_getreg(i2c, OCI2C_STATUS);
if ((i2c->state == STATE_DONE) || (i2c->state == STATE_ERROR)) {
/* stop has been sent */
oc_setreg(i2c, OCI2C_CMD, OCI2C_CMD_IACK);
wake_up(&i2c->wait);
return;
}
/* error? */
if (stat & OCI2C_STAT_ARBLOST) {
i2c->state = STATE_ERROR;
oc_setreg(i2c, OCI2C_CMD, OCI2C_CMD_STOP);
return;
}
if ((i2c->state == STATE_START) || (i2c->state == STATE_WRITE)) {
i2c->state =
(msg->flags & I2C_M_RD) ? STATE_READ : STATE_WRITE;
if (stat & OCI2C_STAT_NACK) {
i2c->state = STATE_ERROR;
oc_setreg(i2c, OCI2C_CMD, OCI2C_CMD_STOP);
return;
}
} else
msg->buf[i2c->pos++] = oc_getreg(i2c, OCI2C_DATA);
/* end of msg? */
if (i2c->pos == msg->len) {
i2c->nmsgs--;
i2c->msg++;
i2c->pos = 0;
msg = i2c->msg;
if (i2c->nmsgs) { /* end? */
/* send start? */
if (!(msg->flags & I2C_M_NOSTART)) {
u8 addr = (msg->addr << 1);
if (msg->flags & I2C_M_RD)
addr |= 1;
i2c->state = STATE_START;
oc_setreg(i2c, OCI2C_DATA, addr);
oc_setreg(i2c, OCI2C_CMD, OCI2C_CMD_START);
return;
} else
i2c->state = (msg->flags & I2C_M_RD)
? STATE_READ : STATE_WRITE;
} else {
i2c->state = STATE_DONE;
oc_setreg(i2c, OCI2C_CMD, OCI2C_CMD_STOP);
return;
}
}
if (i2c->state == STATE_READ) {
oc_setreg(i2c, OCI2C_CMD, i2c->pos == (msg->len-1) ?
OCI2C_CMD_READ_NACK : OCI2C_CMD_READ_ACK);
} else {
oc_setreg(i2c, OCI2C_DATA, msg->buf[i2c->pos++]);
oc_setreg(i2c, OCI2C_CMD, OCI2C_CMD_WRITE);
}
}
[cpp] view
plaincopyprint?
//中断处理函数的处理过程，目前没认真整理过，根据i2c通信协议再好好看看
//然后有时间再总结出来
static void ocores_process(struct ocores_i2c *i2c)
{
struct i2c_msg *msg = i2c->msg;
u8 stat = oc_getreg(i2c, OCI2C_STATUS);
if ((i2c->state == STATE_DONE) || (i2c->state == STATE_ERROR)) {
/* stop has been sent */
oc_setreg(i2c, OCI2C_CMD, OCI2C_CMD_IACK);
wake_up(&i2c->wait);
return;
}
/* error? */
if (stat & OCI2C_STAT_ARBLOST) {
i2c->state = STATE_ERROR;
oc_setreg(i2c, OCI2C_CMD, OCI2C_CMD_STOP);
return;
}
if ((i2c->state == STATE_START) || (i2c->state == STATE_WRITE)) {
i2c->state =
(msg->flags & I2C_M_RD) ? STATE_READ : STATE_WRITE;
if (stat & OCI2C_STAT_NACK) {
i2c->state = STATE_ERROR;
oc_setreg(i2c, OCI2C_CMD, OCI2C_CMD_STOP);
return;
}
} else
msg->buf[i2c->pos++] = oc_getreg(i2c, OCI2C_DATA);
/* end of msg? */
if (i2c->pos == msg->len) {
i2c->nmsgs--;
i2c->msg++;
i2c->pos = 0;
msg = i2c->msg;
if (i2c->nmsgs) { /* end? */
/* send start? */
if (!(msg->flags & I2C_M_NOSTART)) {
u8 addr = (msg->addr << 1);
if (msg->flags & I2C_M_RD)
addr |= 1;
i2c->state = STATE_START;
oc_setreg(i2c, OCI2C_DATA, addr);
oc_setreg(i2c, OCI2C_CMD, OCI2C_CMD_START);
return;
} else
i2c->state = (msg->flags & I2C_M_RD)
? STATE_READ : STATE_WRITE;
} else {
i2c->state = STATE_DONE;
oc_setreg(i2c, OCI2C_CMD, OCI2C_CMD_STOP);
return;
}
}
if (i2c->state == STATE_READ) {
oc_setreg(i2c, OCI2C_CMD, i2c->pos == (msg->len-1) ?
OCI2C_CMD_READ_NACK : OCI2C_CMD_READ_ACK);
} else {
oc_setreg(i2c, OCI2C_DATA, msg->buf[i2c->pos++]);
oc_setreg(i2c, OCI2C_CMD, OCI2C_CMD_WRITE);
}
}
另外还有两个读写寄存器的函数，相信聪明你的绝对是看得明白的~不解释了~
[cpp] view
plaincopyprint?
//这两个函数没什么好解释的了，大家都能看得懂的了
//至于regstep在DTS文件中定义(寄存器的步长)，对应的i2c-specs中寄存器步长为1
static inline void oc_setreg(struct ocores_i2c *i2c, int reg, u8 value)
{
iowrite8(value, i2c->base + reg * i2c->regstep);
}
static inline u8 oc_getreg(struct ocores_i2c *i2c, int reg)
{
return ioread8(i2c->base + reg * i2c->regstep);
}
[cpp] view
plaincopyprint?
//这两个函数没什么好解释的了，大家都能看得懂的了
//至于regstep在DTS文件中定义(寄存器的步长)，对应的i2c-specs中寄存器步长为1
static inline void oc_setreg(struct ocores_i2c *i2c, int reg, u8 value)
{
iowrite8(value, i2c->base + reg * i2c->regstep);
}
static inline u8 oc_getreg(struct ocores_i2c *i2c, int reg)
{
return ioread8(i2c->base + reg * i2c->regstep);
}
先到这里了，至于文章中我觉得没说明白的地方在有时间的时候会补齐的~今天要把食梦者第3季给追完啦~谢谢各位捧场啦~
openrisc-3.1\drivers\i2c\busses\i2c-ocores.c，好~Open之，
然后回想一下之前blog里面写过的关于gpio字符驱动的内容，最后一步我们是把gpio的字符驱动封装成platform机制的，所以，照板煮碗，把代码拉到最后面就可以看到i2c-ocres.c也是同样的道理。
First，定义一个platform_driver结构。
Second，初始化这个结构，指定其probe、remove等函数，并初始化其中的driver变量。
Third，实现其probe、remove等函数。
以上是platform平台驱动的步骤。
然后说明一下i2c总线驱动负责的工作是：
First，申请i2c总线控制器所用到的硬件资源（IO、中断号、内存等等）。
Second，向内核增加一个i2c_adapter数据结构表示这个总线驱动，并且实现i2c_adapter数据结构中的algo成员（即控制i2c控制器的代码）。
所以总线驱动代码的综合效果就是将上面驱动负责的工作写入platform平台驱动，并注册完成i2c总线驱动。
下面来分析一下~
首先，例化关于i2c的平台驱动，这里编写的是对应i2c的总线驱动，所以在例化i2c总线驱动时的of_match_table列表要对应在DTS设备树文件中i2c的总线控制器的compatible，在module加载入kernel时才会按照名称搜索加载i2c的总线驱动。
DTS设备树i2c描述：
[cpp] view
plaincopyprint?
i2c0: ocores@93000000 {
compatible = "opencores,i2c-ocores";
reg = <0x93000000 0x8>;
interrupts = <5>;
regstep = <1>;
clock-frequency = <40000000>;
#address-cells = <1>;
#size-cells = <0>;
eeprom@54 {
compatible = "at24";
reg = <0x54>;
};
};
总线驱动注册代码：
[cpp] view
plaincopyprint?
static struct of_device_id ocores_i2c_match[] = {
{ .compatible = "opencores,i2c-ocores", },
{},
};
MODULE_DEVICE_TABLE(of, ocores_i2c_match);
/* work with hotplug and coldplug */
MODULE_ALIAS("platform:ocores-i2c");
static struct platform_driver ocores_i2c_driver = {
.probe = ocores_i2c_probe,
.remove = __devexit_p(ocores_i2c_remove),
.suspend = ocores_i2c_suspend,
.resume = ocores_i2c_resume,
.driver = {
.owner = THIS_MODULE,
.name = "ocores-i2c",
.of_match_table = ocores_i2c_match,
},
};
static int __init ocores_i2c_init(void)
{
return platform_driver_register(&ocores_i2c_driver);
}
static void __exit ocores_i2c_exit(void)
{
platform_driver_unregister(&ocores_i2c_driver);
}
module_init(ocores_i2c_init);
module_exit(ocores_i2c_exit);
然后，要实现probe、remove等函数
[cpp] view
plaincopyprint?
static int __devinit ocores_i2c_probe(struct platform_device *pdev)
{
struct ocores_i2c *i2c;
struct ocores_i2c_platform_data *pdata;
struct resource *res, *res2;
int ret;
int i;
//获取DTS文件中的IO资源(地址范围)
res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
if (!res)
return -ENODEV;
//获取DTS文件中的中断号资源
res2 = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
if (!res2)
return -ENODEV;
//申请内存
i2c = devm_kzalloc(&pdev->dev, sizeof(*i2c), GFP_KERNEL);
if (!i2c)
return -ENOMEM;
//检查是否有足够内存
if (!devm_request_mem_region(&pdev->dev, res->start,
resource_size(res), pdev->name)) {
dev_err(&pdev->dev, "Memory region busy\n");
return -EBUSY;
}
//i2c控制器wishbone总线物理地址映射到内核地址空间
i2c->base = devm_ioremap_nocache(&pdev->dev, res->start,
resource_size(res));
if (!i2c->base) {
dev_err(&pdev->dev, "Unable to map registers\n");
return -EIO;
}
//例化一个指针指向platform_device的设备的私有数据域，这个数据从编译DTS文件时获取
pdata = pdev->dev.platform_data;
if (pdata) {
i2c->regstep = pdata->regstep;
i2c->clock_khz = pdata->clock_khz;
} else {
ret = ocores_i2c_of_probe(pdev, i2c);
if (ret)
return ret;
}
//初始化i2c控制器，具体可参考i2c_specs
ocores_init(i2c);
//初始化等待队列，目前我还没明白这个，水平有限
init_waitqueue_head(&i2c->wait);
//申请设备使用的中断号，并注册中断函数
ret = devm_request_irq(&pdev->dev, res2->start, ocores_isr, 0,
pdev->name, i2c);
if (ret) {
dev_err(&pdev->dev, "Cannot claim IRQ\n");
return ret;
}
/* hook up driver to tree */
//将i2c保存到platform_device中dev成员的p成员的driver_data数据域中
platform_set_drvdata(pdev, i2c);
i2c->adap = ocores_adapter;
//将i2c保存到i2c_adapter中dev成员的p成员的driver_data数据域中
i2c_set_adapdata(&i2c->adap, i2c);
i2c->adap.dev.parent = &pdev->dev;
i2c->adap.dev.of_node = pdev->dev.of_node;
/* add i2c adapter to i2c tree */
//增加i2c adapter的数据结构
ret = i2c_add_adapter(&i2c->adap);
if (ret) {
dev_err(&pdev->dev, "Failed to add adapter\n");
return ret;
}
/* add in known devices to the bus */
//如果在DTS文件中有多个共享总线驱动的从设备便会枚举出来
if (pdata) {
for (i = 0; i < pdata->num_devices; i++)
i2c_new_device(&i2c->adap, pdata->devices + i);
}
return 0;
}
[cpp] view
plaincopyprint?
static int __devexit ocores_i2c_remove(struct platform_device* pdev)
{
//将之前保存在platform_device中dev成员的p成员的driver_data数据域中的数据取出
struct ocores_i2c *i2c = platform_get_drvdata(pdev);
/* disable i2c logic */
//无效i2c总线控制器
oc_setreg(i2c, OCI2C_CONTROL, oc_getreg(i2c, OCI2C_CONTROL)
& ~(OCI2C_CTRL_EN|OCI2C_CTRL_IEN));
/* remove adapter & data */
//删除完成注册的i2c_adapter
i2c_del_adapter(&i2c->adap);
//删除platform_device中dev成员的p成员的driver_data
platform_set_drvdata(pdev, NULL);
return 0;
}
至于有关电源管理的suspend和resume暂且忽略，内核配置中暂时不去实现。
这样就注册好平台设备驱动。
接下去就在源码中去结合注释和i2c-specs的文档好好看看通信算法处理函数，这也是我们从新开发总线驱动的时候必须去编写的代码~
首先是定义i2c_adapter和其成员变量的algo算法
[cpp] view
plaincopyprint?
static u32 ocores_func(struct i2c_adapter *adap)
{
return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
}
//定义一个i2c_algorithm的数据结构，其中实现控制器通信算法master_xfer
//和functionality(master_xfer通信算法支持的协议)
static const struct i2c_algorithm ocores_algorithm = {
.master_xfer = ocores_xfer,
.functionality = ocores_func,
};
//定义一个i2c_adapter，完成总线控制器的描述，并在probe中向内核注册
static struct i2c_adapter ocores_adapter = {
.owner = THIS_MODULE,
.name = "i2c-ocores",
.class = I2C_CLASS_HWMON | I2C_CLASS_SPD,
.algo = &ocores_algorithm,
};
其中由于这个驱动是基于中断架构的收发，结合源码继续往下看。
首先看看在probe中调用的ocores_init()，完成的是总线控制器的初始化
[cpp] view
plaincopyprint?
//根据i2c-specs文档初始化总线控制器
//对比文档中的寄存器进行操作
static void ocores_init(struct ocores_i2c *i2c)
{
int prescale;
//取出Control register寄存器的值，在i2c-specs中有说明~
u8 ctrl = oc_getreg(i2c, OCI2C_CONTROL);
/* make sure the device is disabled */
//i2c cores禁止中断和无效总线控制器
oc_setreg(i2c, OCI2C_CONTROL, ctrl & ~(OCI2C_CTRL_EN|OCI2C_CTRL_IEN));
//设置i2c总线控制器的通信速率，在i2c-specs文档有计算公式
prescale = (i2c->clock_khz / (5*100)) - 1;
//将速率写入PRERlo和PRERhi寄存器
oc_setreg(i2c, OCI2C_PRELOW, prescale & 0xff);
oc_setreg(i2c, OCI2C_PREHIGH, prescale >> 8);
/* Init the device */
//清除中断标志位，使能总线控制器的中断和使能总线控制器
oc_setreg(i2c, OCI2C_CMD, OCI2C_CMD_IACK);
oc_setreg(i2c, OCI2C_CONTROL, ctrl | OCI2C_CTRL_IEN | OCI2C_CTRL_EN);
}
然后程序调用通信算法时会hold住，在中断中处理数据，然后等待事件集到来，完成通信。
[cpp] view
plaincopyprint?
//发送和接收调用的总线通信算法函数
static int ocores_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
{
//在ocores_i2c中有i2c_adapter成员，而i2c_adapter成员在probe进行时
//已经由i2c_set_adapdata()保存到i2c_adapter中，所以这里取出保存在
//i2c_adapter中dev成员的p成员的driver_data数据域
struct ocores_i2c *i2c = i2c_get_adapdata(adap);
//获取由应用层传入的i2c message
i2c->msg = msgs;
i2c->pos = 0;
i2c->nmsgs = num;
i2c->state = STATE_START;
//根据i2c message类型是读还是写进行器件地址选择和设置LSB的读写位
oc_setreg(i2c, OCI2C_DATA,
(i2c->msg->addr << 1) |
((i2c->msg->flags & I2C_M_RD) ? 1:0));
//根据i2c协议第一次是写器件地址和读写位的组合
oc_setreg(i2c, OCI2C_CMD, OCI2C_CMD_START);
//等待事件集到来，???操作系统没学过，现在恶补
if (wait_event_timeout(i2c->wait, (i2c->state == STATE_ERROR) ||
(i2c->state == STATE_DONE), HZ))
return (i2c->state == STATE_DONE) ? num : -EIO;
else
return -ETIMEDOUT;
}
[cpp] view
plaincopyprint?
[cpp] view
plaincopyprint?
//当总线控制器完成一个byte发送和接收时调用的中断函数
//因为这个驱动采用了中断的方式收发数据
static irqreturn_t ocores_isr(int irq, void *dev_id)
{
struct ocores_i2c *i2c = dev_id;
ocores_process(i2c);
return IRQ_HANDLED;
}
[cpp] view
plaincopyprint?
//当总线控制器完成一个byte发送和接收时调用的中断函数
//因为这个驱动采用了中断的方式收发数据
static irqreturn_t ocores_isr(int irq, void *dev_id)
{
struct ocores_i2c *i2c = dev_id;
ocores_process(i2c);
return IRQ_HANDLED;
}
[cpp] view
plaincopyprint?
//中断处理函数的处理过程，目前没认真整理过，根据i2c通信协议再好好看看
//然后有时间再总结出来
static void ocores_process(struct ocores_i2c *i2c)
{
struct i2c_msg *msg = i2c->msg;
u8 stat = oc_getreg(i2c, OCI2C_STATUS);
if ((i2c->state == STATE_DONE) || (i2c->state == STATE_ERROR)) {
/* stop has been sent */
oc_setreg(i2c, OCI2C_CMD, OCI2C_CMD_IACK);
wake_up(&i2c->wait);
return;
}
/* error? */
if (stat & OCI2C_STAT_ARBLOST) {
i2c->state = STATE_ERROR;
oc_setreg(i2c, OCI2C_CMD, OCI2C_CMD_STOP);
return;
}
if ((i2c->state == STATE_START) || (i2c->state == STATE_WRITE)) {
i2c->state =
(msg->flags & I2C_M_RD) ? STATE_READ : STATE_WRITE;
if (stat & OCI2C_STAT_NACK) {
i2c->state = STATE_ERROR;
oc_setreg(i2c, OCI2C_CMD, OCI2C_CMD_STOP);
return;
}
} else
msg->buf[i2c->pos++] = oc_getreg(i2c, OCI2C_DATA);
/* end of msg? */
if (i2c->pos == msg->len) {
i2c->nmsgs--;
i2c->msg++;
i2c->pos = 0;
msg = i2c->msg;
if (i2c->nmsgs) { /* end? */
/* send start? */
if (!(msg->flags & I2C_M_NOSTART)) {
u8 addr = (msg->addr << 1);
if (msg->flags & I2C_M_RD)
addr |= 1;
i2c->state = STATE_START;
oc_setreg(i2c, OCI2C_DATA, addr);
oc_setreg(i2c, OCI2C_CMD, OCI2C_CMD_START);
return;
} else
i2c->state = (msg->flags & I2C_M_RD)
? STATE_READ : STATE_WRITE;
} else {
i2c->state = STATE_DONE;
oc_setreg(i2c, OCI2C_CMD, OCI2C_CMD_STOP);
return;
}
}
if (i2c->state == STATE_READ) {
oc_setreg(i2c, OCI2C_CMD, i2c->pos == (msg->len-1) ?
OCI2C_CMD_READ_NACK : OCI2C_CMD_READ_ACK);
} else {
oc_setreg(i2c, OCI2C_DATA, msg->buf[i2c->pos++]);
oc_setreg(i2c, OCI2C_CMD, OCI2C_CMD_WRITE);
}
}
[cpp] view
plaincopyprint?
//中断处理函数的处理过程，目前没认真整理过，根据i2c通信协议再好好看看
//然后有时间再总结出来
static void ocores_process(struct ocores_i2c *i2c)
{
struct i2c_msg *msg = i2c->msg;
u8 stat = oc_getreg(i2c, OCI2C_STATUS);
if ((i2c->state == STATE_DONE) || (i2c->state == STATE_ERROR)) {
/* stop has been sent */
oc_setreg(i2c, OCI2C_CMD, OCI2C_CMD_IACK);
wake_up(&i2c->wait);
return;
}
/* error? */
if (stat & OCI2C_STAT_ARBLOST) {
i2c->state = STATE_ERROR;
oc_setreg(i2c, OCI2C_CMD, OCI2C_CMD_STOP);
return;
}
if ((i2c->state == STATE_START) || (i2c->state == STATE_WRITE)) {
i2c->state =
(msg->flags & I2C_M_RD) ? STATE_READ : STATE_WRITE;
if (stat & OCI2C_STAT_NACK) {
i2c->state = STATE_ERROR;
oc_setreg(i2c, OCI2C_CMD, OCI2C_CMD_STOP);
return;
}
} else
msg->buf[i2c->pos++] = oc_getreg(i2c, OCI2C_DATA);
/* end of msg? */
if (i2c->pos == msg->len) {
i2c->nmsgs--;
i2c->msg++;
i2c->pos = 0;
msg = i2c->msg;
if (i2c->nmsgs) { /* end? */
/* send start? */
if (!(msg->flags & I2C_M_NOSTART)) {
u8 addr = (msg->addr << 1);
if (msg->flags & I2C_M_RD)
addr |= 1;
i2c->state = STATE_START;
oc_setreg(i2c, OCI2C_DATA, addr);
oc_setreg(i2c, OCI2C_CMD, OCI2C_CMD_START);
return;
} else
i2c->state = (msg->flags & I2C_M_RD)
? STATE_READ : STATE_WRITE;
} else {
i2c->state = STATE_DONE;
oc_setreg(i2c, OCI2C_CMD, OCI2C_CMD_STOP);
return;
}
}
if (i2c->state == STATE_READ) {
oc_setreg(i2c, OCI2C_CMD, i2c->pos == (msg->len-1) ?
OCI2C_CMD_READ_NACK : OCI2C_CMD_READ_ACK);
} else {
oc_setreg(i2c, OCI2C_DATA, msg->buf[i2c->pos++]);
oc_setreg(i2c, OCI2C_CMD, OCI2C_CMD_WRITE);
}
}
另外还有两个读写寄存器的函数，相信聪明你的绝对是看得明白的~不解释了~
[cpp] view
plaincopyprint?
//这两个函数没什么好解释的了，大家都能看得懂的了
//至于regstep在DTS文件中定义(寄存器的步长)，对应的i2c-specs中寄存器步长为1
static inline void oc_setreg(struct ocores_i2c *i2c, int reg, u8 value)
{
iowrite8(value, i2c->base + reg * i2c->regstep);
}
static inline u8 oc_getreg(struct ocores_i2c *i2c, int reg)
{
return ioread8(i2c->base + reg * i2c->regstep);
}
[cpp] view
plaincopyprint?
//这两个函数没什么好解释的了，大家都能看得懂的了
//至于regstep在DTS文件中定义(寄存器的步长)，对应的i2c-specs中寄存器步长为1
static inline void oc_setreg(struct ocores_i2c *i2c, int reg, u8 value)
{
iowrite8(value, i2c->base + reg * i2c->regstep);
}
static inline u8 oc_getreg(struct ocores_i2c *i2c, int reg)
{
return ioread8(i2c->base + reg * i2c->regstep);
}
先到这里了，至于文章中我觉得没说明白的地方在有时间的时候会补齐的~今天要把食梦者第3季给追完啦~谢谢各位捧场啦~
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