Linux spi驱动分析(一)----总线驱动
2016-08-25 11:04
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一、SPI总线驱动介绍
SPI总线总共需要四根线，包括MOSI、MISO、CLK和CS。本文首先从SPI设备注册开始来讲述SPI总线驱动。
二、设备注册
在系统启动的时候，会按照顺序执行一些初始化程序，比如device_initcall和module_init等宏。这些宏是按照顺序执行的，比如device_initcall的优先级高于module_init，现在我们看下在系统启动的时候注册的spi设备信息。
程序如下：
点击(此处)折叠或打开
/* SPI controller */
#if defined(CONFIG_GSC3280_SPI)
#ifdef CONFIG_SPI1
static struct resource spi1_resources[] = {
[0] = {
.start = GSC3280_SPI1_BASEADDR & 0x1fffffff,
.end = (GSC3280_SPI1_BASEADDR & 0x1fffffff)+ 0x54 - 1 ,
.flags = IORESOURCE_MEM,
},
[1] = {
.start = EXT_GSC3280_SPI1_IRQ,
.end = EXT_GSC3280_SPI1_IRQ,
.flags = IORESOURCE_IRQ,
},
};
static struct platform_device gsc3280_spi1_device = {
.name = "gsc3280-spi",
.id = 1,
#ifdef CONFIG_GSC3280_SPI_DMA
.dev = {
.dma_mask = NULL,
.coherent_dma_mask = DMA_BIT_MASK(32),
.platform_data = NULL,
},
#endif
.resource = spi1_resources,
.num_resources = ARRAY_SIZE(spi1_resources),
};
#endif
/* SPI devices */
#if defined(CONFIG_SPI_FLASH_W25Q)
static struct gsc3280_spi_info w25q_spi1_dev_platdata = {
.pin_cs = 87,
.num_cs = 1,
.cs_value = 0,
.lsb_flg = 0,
.bits_per_word = 8,
};
#endif
static struct spi_board_info gsc3280_spi_devices[] = {
#if defined(CONFIG_SPI_FLASH_W25Q)
{
.modalias = "spi-w25q",
.bus_num = 1,
.chip_select = 3,
.mode = SPI_MODE_3,
.max_speed_hz = 5 * 1000 * 1000,
.controller_data = &w25q_spi1_dev_platdata,
},
#endif
};
static int __init gsc3280_spi_devices_init(void)
{
spi_register_board_info(gsc3280_spi_devices, ARRAY_SIZE(gsc3280_spi_devices));
return 0;
}
device_initcall(gsc3280_spi_devices_init);
#endif //end #if defined(CONFIG_GSC3280_SPI)
注意到此处共定义两个设备，使用spi_register_board_info()函数对spi设备进行注册，程序如下：
点击(此处)折叠或打开
int __init
spi_register_board_info(struct spi_board_info const *info, unsigned n)
{
struct boardinfo *bi;
int i;
bi = kzalloc(n * sizeof(*bi), GFP_KERNEL);
if (!bi)
return -ENOMEM;
for (i = 0; i < n; i++, bi++, info++) {
struct spi_master *master;
memcpy(&bi->board_info, info, sizeof(*info));
mutex_lock(&board_lock);
list_add_tail(&bi->list, &board_list);
list_for_each_entry(master, &spi_master_list, list)
spi_match_master_to_boardinfo(master, &bi->board_info);
mutex_unlock(&board_lock);
}
return 0;
}
对于此处，n为1，在程序中首先创建相应的内存，在for循环中，将信息保存到内存中，然后插入board_list链表，接着遍历
spi_master_list链表，注意此处，由于device_initcall的优先级高于module_init，所以此时spi_master_list链表为空，那么还
不能调用spi_match_master_to_boardinfo函数创建spi设备，具体的创建设备将在spi总线驱动的探测函数中，使用spi_register_master()
函数创建设备。
三、总线驱动探测、退出和电源管理函数
3.1、探测函数gsc3280_spi_probe
程序如下：点击(此处)折叠或打开
static int __init gsc3280_spi_probe(struct platform_device *pdev)
{
int ret = 0;
struct gsc3280_spi *gscs;
struct spi_master *master;
struct resource *mem, *ioarea;
DBG("############\n");
DBG("gsc3280 spi probe start\n");
master = spi_alloc_master(&pdev->dev, sizeof(struct
gsc3280_spi));
if (!master) {
ret = -ENOMEM;
DBG("!!!!spi_alloc_master error\n");
goto exit;
}
gscs = spi_master_get_devdata(master);
memset(gscs, 0, sizeof(struct gsc3280_spi));
gscs->master = spi_master_get(master);
mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
if (!mem) {
DBG("!!!!no mem resource!\n");
ret = -EINVAL;
goto err_kfree;
}
ioarea = request_mem_region(mem->start, resource_size(mem), pdev->name);
if (!ioarea) {
DBG("!!!!SPI region already claimed!\n");
ret = -EBUSY;
goto err_kfree;
}
gscs->regs = ioremap_nocache(mem->start, resource_size(mem));
if (!gscs->regs) {
DBG("!!!!SPI ioremap error!\n");
ret = -ENOMEM;
goto err_release_reg;
}
DBG("gscs->regs = 0x%p\n", gscs->regs);
gscs->irq = platform_get_irq(pdev, 0);
if (gscs->irq < 0) {
DBG("!!!!no irq resource!\n");
ret = gscs->irq;
goto err_unmap;
}
ret = request_irq(gscs->irq, gsc3280_spi_irq, IRQF_DISABLED, dev_name(&pdev->dev), gscs);
if (ret < 0) {
DBG("!!!!can not get IRQ!\n");
goto err_irq;
}
gscs->clk = clk_get(NULL, "spi1");
if (IS_ERR(gscs->clk)) {
DBG("!!!!failed to find spi1 clock source!\n");
ret = PTR_ERR(gscs->clk);
goto err_irq;
}
gscs->max_freq = clk_get_rate(gscs->clk);
DBG("rate is %d\n", gscs->max_freq);
clk_enable(gscs->clk);
gscs->bus_num = pdev->id;
gscs->num_cs = 4;
gscs->prev_chip = NULL;
INIT_LIST_HEAD(&gscs->queue);
spin_lock_init(&gscs->slock);
#ifdef CONFIG_GSC3280_SPI_DMA
gscs->dma_priv = pdev->dev.platform_data = &spi_platform_data;
if (!gscs->dma_priv)
goto err_clk; //return -ENOMEM;
gscs->dma_ops = &gscs_dma_ops;
gscs->dma_inited = 0;
gscs->dma_addr = (dma_addr_t)(gscs->regs + 0x24) & 0x1fffffff;
#endif
platform_set_drvdata(pdev, master);
master->mode_bits = SPI_CPOL | SPI_CPHA;
master->bus_num = gscs->bus_num;
master->num_chipselect = gscs->num_cs;
master->cleanup = gsc3280_spi_cleanup;
master->setup = gsc3280_spi_setup;
master->transfer = gsc3280_spi_transfer;
gsc3280_spi_hw_init(gscs);
#ifdef CONFIG_SPI_GSC3280_DMA
if (gscs->dma_ops && gscs->dma_ops->dma_init) {
ret = gscs->dma_ops->dma_init(gscs);
if (ret) {
dev_warn(&master->dev, "DMA
init failed\n");
gscs->dma_inited = 0;
}
}
#endif
ret = gsc3280_init_queue(gscs);
if (ret != 0) {
DBG("!!!!problem initializing queue!\n");
goto err_diable_hw;
}
ret = gsc3280_start_queue(gscs);
if (ret != 0) {
DBG("!!!!problem starting queue!\n");
goto err_queue_alloc;
}
ret = spi_register_master(master);
if (ret != 0) {
DBG("!!!!register spi master error!\n");
goto err_queue_alloc;
}
DBG("gsc3280 spi probe success\n");
DBG("############\n");
return 0;
//err_free_master:
//spi_master_put(master);
err_queue_alloc:
gsc3280_spi_destroy_queue(gscs);
#ifdef CONFIG_SPI_GSC3280_DMA
if (gscs->dma_ops && gscs->dma_ops->dma_exit)
gscs->dma_ops->dma_exit(gscs);
#endif
err_diable_hw:
gsc3280_enable_spi(gscs, GSC_SPI_DISABLE);
//err_clk:
clk_disable(gscs->clk);
clk_put(gscs->clk);
err_irq:
free_irq(gscs->irq, gscs);
err_unmap:
iounmap(gscs->regs);
err_release_reg:
release_mem_region(mem->start, resource_size(mem));
err_kfree:
kfree(gscs);
kfree(master);
exit:
printk(KERN_ERR "!!!!!!gsc3280 probe error!!!!!!\n");
return ret;
}
说明：
1) 首先是总线资源的注册，包括申请IO空间和中断。
2) 接下来注册了中断函数。
3) 然后注册了spi_master所需要的函数，包括清除、设置和传输等函数，在四中会讲述。
4) gsc3280_spi_hw_init函数初始化了SPI总线寄存器，接下来讲述。
5) 总线驱动采用queue机制实现多设备SPI读写，接下来初始化和启动了queue，接下来讲述。
6) 使用spi_register_master函数注册master，此函数即实现创建了SPI设备结构体，接下来讲述。
SPI总线寄存器初始化函数gsc3280_spi_hw_init：
点击(此处)折叠或打开
/* Restart the controller, disable all interrupts, clean fifo */
static void gsc3280_spi_hw_init(struct gsc3280_spi *gscs)
{
gsc3280_enable_spi(gscs, GSC_SPI_DISABLE);
gsc3280_spi_mask_intr(gscs, GSC_SPI_SR_MASK);
if (!gscs->fifo_len) {
gscs->fifo_len = 0x10;
__raw_writew(0x00, gscs->regs + GSC_SPI_TXFTLR);
__raw_writew(0x00, gscs->regs + GSC_SPI_RXFTLR);
}
gsc3280_enable_spi(gscs, GSC_SPI_ENABLE);
}
由程序可以看出，此函数首先禁止SPI，屏蔽中断，然后设置fifo深度，最后使能SPI。
初始化queue函数gsc3280_init_queue：
点击(此处)折叠或打开
static int __devinit gsc3280_init_queue(struct gsc3280_spi *gscs)
{
gscs->queue_state = GSC_SPI_QUEUE_STOP;
gscs->busy = 0;
tasklet_init(&gscs->pump_transfers, gsc3280_spi_pump_transfers, (unsigned
long)gscs);
INIT_WORK(&gscs->pump_messages, gsc3280_spi_pump_messages);
gscs->workqueue = create_singlethread_workqueue(dev_name(gscs->master->dev.parent));
if (gscs->workqueue == NULL) {
DBG("!!!!create_singlethread_workqueue error!\n");
return -EBUSY;
}
else
return 0;
}
由程序看出，此函数主要完成初始化队列的作用，包括对queue函数的初始化，最后创建了queue。
开始queue函数gsc3280_start_queue：
点击(此处)折叠或打开
static int gsc3280_start_queue(struct gsc3280_spi *gscs)
{
unsigned long flags;
spin_lock_irqsave(&gscs->lock, flags);
if ((gscs->run == GSC_SPI_QUEUE_RUN) || gscs->busy) {
spin_unlock_irqrestore(&gscs->lock, flags);
return -EBUSY;
}
gscs->run = GSC_SPI_QUEUE_RUN;
gscs->cur_msg = NULL;
gscs->cur_transfer = NULL;
gscs->cur_chip = NULL;
gscs->prev_chip = NULL;
spin_unlock_irqrestore(&gscs->lock, flags);
queue_work(gscs->workqueue, &gscs->pump_messages);
return 0;
}
此函数首先对queue的状态进行判断，然后初始化相关成员变量，最后调度queue。
最后看下master注册函数spi_register_master：
点击(此处)折叠或打开
int spi_register_master(struct spi_master *master)
{
static atomic_t dyn_bus_id = ATOMIC_INIT((1<<15) - 1);
struct device *dev = master->dev.parent;
struct boardinfo *bi;
int status = -ENODEV;
int dynamic = 0;
if (!dev)
return -ENODEV;
/* even if it's just one always-selected device, there
must
* be at least one chipselect
*/
if (master->num_chipselect == 0)
return -EINVAL;
/* convention: dynamically assigned bus IDs count down from the max */
if (master->bus_num < 0) {
/* FIXME switch to an IDR based scheme, something like
* I2C now uses, so we can't run out of "dynamic" IDs
*/
master->bus_num = atomic_dec_return(&dyn_bus_id);
dynamic = 1;
}
spin_lock_init(&master->bus_lock_spinlock);
mutex_init(&master->bus_lock_mutex);
master->bus_lock_flag = 0;
/* register the device, then userspace will see it.
* registration fails if the bus ID is in use.
*/
dev_set_name(&master->dev, "spi%u", master->bus_num);
status = device_add(&master->dev);
if (status < 0)
goto done;
dev_dbg(dev, "registered master %s%s\n", dev_name(&master->dev),
dynamic ? " (dynamic)" : "");
mutex_lock(&board_lock);
list_add_tail(&master->list, &spi_master_list);
list_for_each_entry(bi, &board_list, list)
spi_match_master_to_boardinfo(master, &bi->board_info);
mutex_unlock(&board_lock);
status = 0;
/* Register devices from the device tree */
of_register_spi_devices(master);
done:
return status;
}
EXPORT_SYMBOL_GPL(spi_register_master);
说明：
1) 首先对master成员变量进行检查。
2) 初始化成员变量。
3) 将master->list插入到spi_master_list链表中。
4) 语句list_for_each_entry(bi, &board_list, list)实现遍历board_list链表，在二设备注册中已经讲述了将设备插入到
board_list链表中。此时的board_list链表不为空，已经有相应设备结构体信息了。
5) 语句spi_match_master_to_boardinfo(master, &bi->board_info);实现设备的创建，函数程序如下：
点击(此处)折叠或打开
static void spi_match_master_to_boardinfo(struct spi_master *master,
struct spi_board_info *bi)
{
struct spi_device *dev;
if (master->bus_num != bi->bus_num)
return;
dev = spi_new_device(master, bi);
if (!dev)
dev_err(master->dev.parent, "can't
create new device for %s\n",
bi->modalias);
}
说明：
1) 函数首先判断master的总线号和设备的总线号是否相等，如果不等直接返回。
2) 函数spi_new_device(master, bi);实现设备创建，如下：
点击(此处)折叠或打开
struct spi_device *spi_new_device(struct spi_master *master,
struct spi_board_info *chip)
{
struct spi_device *proxy;
int status;
/* NOTE: caller did any chip->bus_num checks necessary.
*
* Also, unless we change the return value convention to use
* error-or-pointer (not NULL-or-pointer), troubleshootability
* suggests syslogged diagnostics are best here (ugh).
*/
proxy = spi_alloc_device(master);
if (!proxy)
return NULL;
WARN_ON(strlen(chip->modalias) >= sizeof(proxy->modalias));
proxy->chip_select = chip->chip_select;
proxy->max_speed_hz = chip->max_speed_hz;
proxy->mode = chip->mode;
proxy->irq = chip->irq;
strlcpy(proxy->modalias, chip->modalias, sizeof(proxy->modalias));
proxy->dev.platform_data = (void *) chip->platform_data;
proxy->controller_data = chip->controller_data;
proxy->controller_state = NULL;
status = spi_add_device(proxy);
if (status < 0) {
spi_dev_put(proxy);
return NULL;
}
return proxy;
}
EXPORT_SYMBOL_GPL(spi_new_device);
struct spi_device *spi_alloc_device(struct spi_master *master)
{
struct spi_device *spi;
struct device *dev = master->dev.parent;
if (!spi_master_get(master))
return NULL;
spi = kzalloc(sizeof *spi, GFP_KERNEL);
if (!spi) {
dev_err(dev, "cannot alloc spi_device\n");
spi_master_put(master);
return NULL;
}
spi->master = master;
spi->dev.parent = dev;
spi->dev.bus = &spi_bus_type;
spi->dev.release = spidev_release;
device_initialize(&spi->dev);
return spi;
}
EXPORT_SYMBOL_GPL(spi_alloc_device);
说明：
1) 首先调用spi_alloc_device函数创建设备内存，从spi_alloc_device函数中可以看到，首先申请内存，然后对设备程序进行赋值。
2) 接下来将芯片的信息赋值给设备结构体，包括片选、最大速率、模式、中断和名称等。此处名称尤为重要，在spi设备的注册函数
spi_register_driver中，就是通过名称找到相应的设备信息结构体的。
3) 程序status = spi_add_device(proxy);实现添加spi设备信息。此函数在--Linux spi驱动分析(二)----spi内核中讲述。
3.2、移除函数gsc3280_spi_remove
程序如下：点击(此处)折叠或打开
void __exit gsc3280_spi_remove(struct platform_device *pdev)
{
int status = 0;
struct spi_master *master = platform_get_drvdata(pdev);
struct gsc3280_spi *gscs = spi_master_get_devdata(master);
if (!gscs)
return;
status = gsc3280_spi_destroy_queue(gscs);
if (status != 0)
dev_err(&gscs->master->dev, "gsc3280_spi_remove:
workqueue will not "
"complete, message memory not freed\n");
#ifdef CONFIG_SPI_GSC3280_DMA
if (gscs->dma_ops && gscs->dma_ops->dma_exit)
gscs->dma_ops->dma_exit(gscs);
#endif
gsc3280_enable_spi(gscs, GSC_SPI_DISABLE);
free_irq(gscs->irq, gscs);
iounmap(gscs->regs);
spi_unregister_master(gscs->master);
}
说明：
1) 首先获得总线结构体
2) 然后删除queue
3) 最后禁止SPI，释放中断和IO，最后注销master。
3.3、挂起函数gsc3280_spi_suspend
程序如下：点击(此处)折叠或打开
static int gsc3280_spi_suspend(struct platform_device *pdev, pm_message_t
mesg)
{
int ret = 0;
struct spi_master *master = platform_get_drvdata(pdev);
struct gsc3280_spi *gscs = spi_master_get_devdata(master);
ret = gsc3280_spi_stop_queue(gscs);
if (ret)
return ret;
gsc3280_enable_spi(gscs, GSC_SPI_DISABLE);
return ret;
}
程序中首先停止queue，然后禁止SPI。
停止queue函数内容如下：
点击(此处)折叠或打开
static int gsc3280_spi_stop_queue(struct gsc3280_spi *gscs)
{
int status = 0;
unsigned long flags;
unsigned limit = 50;
spin_lock_irqsave(&gscs->lock, flags);
while ((!list_empty(&gscs->queue) || gscs->busy) && limit--) {
spin_unlock_irqrestore(&gscs->lock, flags);
msleep(10);
spin_lock_irqsave(&gscs->lock, flags);
}
if (!list_empty(&gscs->queue) || gscs->busy)
status = -EBUSY;
else
gscs->queue_state = GSC_SPI_QUEUE_STOP;
spin_unlock_irqrestore(&gscs->lock, flags);
return status;
}
程序首先遍历queue链表，查看是否还有queue没有执行，总共尝试50次，如果还有queue没有执行或者设备忙，则错误返回，否
则置正确queue状态。
3.4、恢复函数gsc3280_spi_resume
程序如下：点击(此处)折叠或打开
static int gsc3280_spi_resume(struct platform_device *pdev)
{
int ret = 0;
struct spi_master *master = platform_get_drvdata(pdev);
struct gsc3280_spi *gscs = spi_master_get_devdata(master);
gsc3280_spi_hw_init(gscs);
ret = gsc3280_start_queue(gscs);
if (ret)
dev_err(&gscs->master->dev, "fail
to start queue (%d)\n", ret);
return ret;
}
程序主要初始化SPI寄存器，然后开始运行queue。
四、spi master支持函数
4.1、清除函数gsc3280_spi_cleanup
点击(此处)折叠或打开static void gsc3280_spi_cleanup(struct spi_device *spi)
{
struct chip_data *chip = spi_get_ctldata(spi);
kfree(chip);
}
程序首先获取设备指针，然后释放内存。
4.2、设置函数gsc3280_spi_setup
此函数是一个回调函数，spi核心中的spi_setup()函数会调用此函数，程序如下：点击(此处)折叠或打开
/* This may be called twice for each spi dev */
static int gsc3280_spi_setup(struct spi_device *spi)
{
int ret = 0;
struct chip_data *chip = NULL;
struct gsc3280_spi_info *chip_info = NULL;
DBG("######gsc3280 spi bus setup start######\n");
chip = spi_get_ctldata(spi); /* Only
alloc on first setup */
if (!chip) {
chip = kzalloc(sizeof(struct chip_data), GFP_KERNEL);
if (!chip) {
DBG("!!!!kzalloc error!\n");
ret = -ENOMEM;
goto exit;
}
}
chip_info = spi->controller_data;
/* chip_info doesn't always exist */
if (chip_info) {
#ifdef CONFIG_GSC3280_SPI_DMA
chip->poll_mode = chip_info->poll_mode;
chip->enable_dma = chip_info->enable_dma;
#endif
chip->pin_cs = chip_info->pin_cs;
chip->cs_value = chip_info->cs_value;
chip->bits_per_word = chip_info->bits_per_word;
chip->lsb_flg = chip_info->lsb_flg;
gpio_request(chip->pin_cs, spi->modalias);
if (chip->cs_value == 0)
gpio_direction_output(chip->pin_cs, 1);
else
gpio_direction_output(chip->pin_cs, 0);
}
if (spi->bits_per_word == 8) {
chip->n_bytes = 1;
#ifdef CONFIG_GSC3280_SPI_DMA
chip->dma_width = 1;
#endif
} else if (spi->bits_per_word == 16) {
chip->n_bytes = 2;
#ifdef CONFIG_GSC3280_SPI_DMA
chip->dma_width = 2;
#endif
} else {
DBG("!!!!spi->bits_per_word = %d error!\n", spi->bits_per_word);
ret = -EINVAL;
goto exit;
}
if (!spi->max_speed_hz) {
DBG("!!!!spi->max_speed_hz = %d, error!\n", spi->max_speed_hz);
ret = -EINVAL;
goto exit;
}
chip->speed_hz = spi->max_speed_hz;
chip->cr = (chip->lsb_flg << GSC_SPI_CTL_BITS_NUM) | (spi->mode << GSC_SPI_CTL_MOD)
| ((chip->bits_per_word - 1) << GSC_SPI_CTL_DSS);
spi_set_ctldata(spi, chip);
exit:
if (ret != 0)
DBG("!!!!gsc3280 spi bus setup error!\n");
else
DBG("######gsc3280 spi bus setup success######\n");
return ret;
}
说明：
1) 首先判断参数，如果参数错误，直接返回。
2) 获取spi控制数据，如果没有，则申请内存创建设备。
3) 接下来根据实际情况对设备结构体赋值。
4.3、传输函数gsc3280_spi_transfer
此函数尤为重要，SPI设备传输数据时，就是调用此函数实现数据传输的，此函数主要完成结构体成员变量的初始化，具体的传输在中断中进行。
点击(此处)折叠或打开
/* spi driver call this function transfer data */
static int gsc3280_spi_transfer(struct spi_device *spi, struct spi_message *msg)
{
unsigned long flags = 0;
struct gsc3280_spi *gscs = spi_master_get_devdata(spi->master);
DBG("####gsc3280 spi transfer start####\n");
if (gscs->queue_state == GSC_SPI_QUEUE_STOP) {
DBG("!!!!queue is stop!\n");
return -ESHUTDOWN;
}
msg->actual_length = 0;
msg->status = -EINPROGRESS;
msg->state = START_STATE;
spin_lock_irqsave(&gscs->slock, flags);
list_add_tail(&msg->queue, &gscs->queue);
spin_unlock_irqrestore(&gscs->slock, flags);
//writel(0x3f, (volatile unsigned int *)(0xbc04a000 + 0x38)); //max
divid freq
if (gscs->cur_transfer || gscs->cur_msg) {
//DBG("gsc3280_spi_transfer: cur transfer or msg not empty\n");
} else {
//DBG("gsc3280_spi_transfer: no cur transfer and msg\n");
queue_work(gscs->workqueue, &gscs->pump_messages);
}
DBG("####gsc3280 spi transfer success####\n");
return 0;
}
说明：
1) 首先判断queue状态，如果是停止状态，则退出。
2) 对传送结构体成员变量赋值。
3) 判断当前是否有数据在收发，如果有，就先直接返回。
4) 如果没有，则调用queue_work()函数，调度函数gsc3280_spi_pump_messages()。程序如下：
点击(此处)折叠或打开
/*
* when call this function, no msg transfering
* deal one msg when call this funciton once.
*
*/
static void gsc3280_spi_pump_messages(struct work_struct *work)
{
unsigned long flags = 0;
struct gsc3280_spi *gscs = container_of(work, struct gsc3280_spi, pump_messages);
DBG("####gsc3280_spi_pump_messages####\n");
if (list_empty(&gscs->queue) || (gscs->queue_state == GSC_SPI_QUEUE_STOP)) {
if (gscs->queue_state == GSC_SPI_QUEUE_STOP)
DBG("!!!!queue is stop!\n");
else
DBG("msg is finished!\n");
gscs->busy = 0;
return;
}
spin_lock_irqsave(&gscs->slock, flags);
gscs->cur_msg = list_entry(gscs->queue.next, struct
spi_message, queue);
if (!gscs->cur_msg) {
spin_unlock_irqrestore(&gscs->slock, flags);
DBG("!!!!gsc3280_spi_pump_messages: current no msg!\n");
return;
}
list_del_init(&gscs->cur_msg->queue);
gscs->cur_msg->state = RUNNING_STATE;
gscs->cur_chip = spi_get_ctldata(gscs->cur_msg->spi);
gscs->n_bytes = gscs->cur_chip->n_bytes;
gscs->busy = 1;
spin_unlock_irqrestore(&gscs->slock, flags);
DBG("cs select enable\n");
if (gscs->cur_chip->cs_value == 0) {
gpio_set_value(gscs->cur_chip->pin_cs, 0);
}
else
gpio_set_value(gscs->cur_chip->pin_cs, 1);
/* get first transfer */
gscs->cur_transfer = list_entry(gscs->cur_msg->transfers.next, struct
spi_transfer, transfer_list);
if (!gscs->cur_transfer) {
DBG("!!!!gsc3280_spi_pump_transfers: current no transfer!\n");
return;
}
tasklet_schedule(&gscs->pump_transfers);
return;
}
说明：
1) 此函数在两种情况下会被调用：
a) 当第一次开始SPI传输时，会调用此函数，设置message结构体变量。
b) 当传输完一个message后，如果判断还有message没有被传输，则调用此函数获取新的message。
2) 程序首先对变量进行检查，有两种退出情况，第一种是队列已经处于停止状态，第二种是传输msg链表为空。
3) 上锁，获取新的传输message，如果获取失败，直接解锁退出。
4) 如果获取msg成功，先删除获取成功msg的链表，然后对SPI总线驱动结构体变量赋初值。
5) 解锁，使能片选信号CS。
6) 获取传输的第一个transfer。
7) 调度gsc3280_spi_pump_transfers函数，函数如下：
点击(此处)折叠或打开
/* when call this function,the
cur_msg is the new msg */
static void gsc3280_spi_pump_transfers(unsigned long data)
{
int clk_div = 0;
u32 imask = 0, cr = 0;
unsigned long flags = 0;
struct spi_transfer *previous = NULL;
struct gsc3280_spi *gscs = (struct gsc3280_spi *)data;
//DBG("gsc3280_spi_pump_transfers\n");
if (gscs->cur_msg->state == ERROR_STATE) {
DBG("!!!!pump_transfers:cur msg state error!\n");
gscs->cur_msg->status = -EIO;
goto early_exit;
}
/* Handle end of message */
if (gscs->cur_msg->state == DONE_STATE) {
gscs->cur_msg->status = 0;
goto early_exit;
}
/* Delay if requested at end of transfer*/
if (gscs->cur_msg->state == RUNNING_STATE) {
previous = list_entry(gscs->cur_transfer->transfer_list.prev, struct
spi_transfer, transfer_list);
if (previous->delay_usecs)
udelay(previous->delay_usecs);
}
#ifdef CONFIG_SPI_GSC3280_DMA
gscs->dma_width = gscs->cur_chip->dma_width;
gscs->rx_dma = gscs->cur_transfer->rx_dma;
gscs->tx_dma = gscs->cur_transfer->tx_dma;
#endif
/* Handle per transfer options for bpw and speed */
if (gscs->cur_transfer->speed_hz) {
if (gscs->cur_transfer->speed_hz != gscs->cur_chip->speed_hz) {
if (gscs->cur_transfer->speed_hz > gscs->max_freq) {
printk(KERN_ERR "SPI1: unsupported freq: %dHz\n", gscs->cur_transfer->speed_hz);
gscs->cur_msg->status = -EIO;
return;
} else
gscs->cur_chip->speed_hz = gscs->cur_transfer->speed_hz;
}
}
if (gscs->cur_transfer->bits_per_word) {
switch (gscs->cur_transfer->bits_per_word) {
case 8:
case 16:
gscs->n_bytes = gscs->cur_transfer->bits_per_word >> 3;
#ifdef CONFIG_SPI_GSC3280_DMA
gscs->dma_width = gscs->n_bytes;
#endif
break;
default:
printk(KERN_ERR "SPI1: unsupported bits:" "%db\n", gscs->cur_transfer->bits_per_word);
gscs->cur_msg->status = -EIO;
return;
}
}
clk_div = gscs->max_freq / gscs->cur_transfer->speed_hz;
clk_div = clk_div / 2 - 1;
if (clk_div < 0)
clk_div = 0;
gscs->cur_chip->clk_div = (u16)clk_div;
cr = gscs->cur_chip->cr | GSC_SPI_CTL_EN;
writel(cr, gscs->regs + GSC_SPI_CTRL); /* enable
spi */
writel(gscs->cur_chip->clk_div, gscs->regs + GSC_SPI_SEABAUR);
spin_lock_irqsave(&gscs->slock, flags);
//gscs->n_bytes = gscs->cur_chip->n_bytes;
gscs->tx = (void *)gscs->cur_transfer->tx_buf;
gscs->tx_end = gscs->tx + gscs->cur_transfer->len;
gscs->rx = gscs->cur_transfer->rx_buf;
gscs->rx_end = gscs->rx + gscs->cur_transfer->len;
gscs->cs_change = gscs->cur_transfer->cs_change;
gscs->len = gscs->cur_transfer->len;
spin_unlock_irqrestore(&gscs->slock, flags);
imask |= SPI_INT_TX_H_OVER | SPI_INT_RX_L_OVER | SPI_INT_RX_H_OVER | SPI_INT_RX_FULL;
if (gscs->tx != NULL) {
imask |= SPI_INT_TX_EMPTY;
}
gsc3280_spi_umask_intr(gscs, imask);
#ifdef CONFIG_GSC3280_SPI_DMA
/* Check if current transfer is a DMA transaction */
gscs->dma_mapped = map_dma_buffers(gscs);
/* Interrupt mode we only need set the TXEI IRQ, as TX/RX
always happen syncronizely */
if (!gscs->dma_mapped && !gscs->cur_chip->poll_mode) {
//int templen = gscs->len / gscs->n_bytes;
//txint_level = gscs->fifo_len / 2;
//txint_level = (templen > txint_level) ? txint_level : templen;
}
if (gscs->dma_mapped)
gscs->dma_ops->dma_transfer(gscs, cs_change);
if (gscs->cur_chip->poll_mode)
gsc3280_spi_poll_transfer(gscs);
#endif
return;
early_exit:
gsc3280_spi_giveback(gscs);
return;
}
说明：
1) 首先对msg变量进行检测。
2) 如果变量正确，获取此次传输的分频系数和每次传输几个字节。
3) 设置SPI控制寄存器和分频寄存器，
4) 设置SPI总线驱动结构体中的传输或者接收数据指针，打开中断，开始数据传输。
5) 每传输一个transfer，都会调用此函数一次。
实际的传输数据在中断中进行，程序如下：
点击(此处)折叠或打开
/* this is transfer message function */
static irqreturn_t gsc3280_spi_irq(int irq, void *dev_id)
{
struct gsc3280_spi *gscs = dev_id;
u32 irq_status = __raw_readw(gscs->regs + GSC_SPI_ISR);
//DBG("gsc3280_spi_irq\n");
//DBG("sys_ctl0 = 0x%x\n", readl((volatile
unsigned int *)(0xbc04a000 + 0x08)));
//DBG("clddiv_spi1 = 0x%x\n", readl((volatile
unsigned int *)(0xbc04a000 + 0x38)));
//DBG("imux_cfg0 = 0x%x\n", readl((volatile
unsigned int *)(0xbc04a000 + 0xb0)));
DBG("cr = 0x%x\n", __raw_readw(gscs->regs + GSC_SPI_CTRL));
DBG("imsr = 0x%x, irq_status = 0x%x\n", __raw_readl(gscs->regs + GSC_SPI_IMSR), irq_status);
if (!irq_status ) {
DBG("!!!!gsc3280_spi_irq: no irq!\n");
return IRQ_NONE;
}
if (!gscs->cur_msg) {
DBG("!!!!gsc3280_spi_irq: no msg!\n");
gsc3280_spi_mask_intr(gscs, SPI_INT_TX_EMPTY | SPI_INT_RX_FULL);
return IRQ_HANDLED;
}
if (irq_status & (SPI_INT_TX_H_OVER | SPI_INT_RX_L_OVER | SPI_INT_RX_H_OVER)) {
DBG("!!!!gsc3280_spi_irq: fifo overrun/underrun!\n");
__raw_writew(0x0e, gscs->regs + GSC_SPI_ISR);
gscs->cur_msg->state = ERROR_STATE;
gscs->cur_msg->status = -EIO;
queue_work(gscs->workqueue, &gscs->pump_messages);
return IRQ_HANDLED;
}
if (irq_status & SPI_INT_RX_FULL) {
spi_gsc_read(gscs);
return IRQ_HANDLED;
}
if (irq_status & SPI_INT_TX_EMPTY) {
spi_gsc_write(gscs);
}
return IRQ_HANDLED;
}
说明：
1) 首先读取中断状态，如果是空中断，退出中断。
2) 判断当前是否有msg在传输，如果没有，退出中断。
3) 判断是否是错误中断，包括溢出等，如果是，屏蔽中断，退出中断。
4) 如果是接收满中断，则首先接收数据。然后退出中断。
4) 如果是发送空中断，则发送数据，发送完成后，退出中断。
现在看下发送数据函数spi_gsc_write()：
点击(此处)折叠或打开
static void gsc3280_writer(struct gsc3280_spi *gscs)
{
u16 txw = 0;
unsigned long flags = 0;
u32 max = gsc3280_spi_tx_max(gscs);
//DBG("max = %d, gscs->n_bytes = 0x%x", max, gscs->n_bytes);
spin_lock_irqsave(&gscs->slock, flags);
while (max--) {
if (gscs->n_bytes == 1)
txw = *(u8 *)(gscs->tx);
else
txw = *(u16 *)(gscs->tx);
DBG("txw = 0x%x\n", txw);
writel(txw, gscs->regs + GSC_SPI_DA_S);
gscs->tx += gscs->n_bytes;
}
spin_unlock_irqrestore(&gscs->slock, flags);
}
static void spi_gsc_write(struct gsc3280_spi *gscs)
{
//DBG("spi_gsc_write\n");
gsc3280_spi_mask_intr(gscs, GSC_SPI_SR_MASK);
gsc3280_writer(gscs);
if (gscs->tx_end == gscs->tx) {
gsc3280_spi_xfer_done(gscs);
}
else {
gsc3280_spi_umask_intr(gscs, GSC_SPI_SR_MASK);
}
}
说明：
1) 首先屏蔽中断。
2) 发送数据。
3) 如果发送完成，执行gsc3280_spi_xfer_done(gscs)函数。
4) 如果没有完成，打开中断，继续发数据。
对于gsc3280_spi_xfer_done()函数，如下：
点击(此处)折叠或打开
static void *gsc3280_spi_next_transfer(struct gsc3280_spi *gscs)
{
struct spi_message *msg = gscs->cur_msg;
struct spi_transfer *trans = gscs->cur_transfer;
if (trans->transfer_list.next != &msg->transfers) {
gscs->cur_transfer = list_entry(trans->transfer_list.next, struct
spi_transfer, transfer_list);
return RUNNING_STATE;
} else
return DONE_STATE;
}
static void gsc3280_spi_xfer_done(struct gsc3280_spi *gscs)
{
//DBG("gsc3280_spi_xfer_done\n");
//DBG("irq_status = 0x%x\n", __raw_readw(gscs->regs + GSC_SPI_ISR));
//DBG("imsr = 0x%x\n", __raw_readl(gscs->regs + GSC_SPI_IMSR));
/* Update total byte transferred return count actual bytes read */
gscs->cur_msg->actual_length += gscs->len;
/* Move to next transfer */
gscs->cur_msg->state = gsc3280_spi_next_transfer(gscs);
if (gscs->cur_msg->state == DONE_STATE) {
/* Handle end of message */
gscs->cur_msg->status = 0;
gsc3280_spi_giveback(gscs);
} else {
tasklet_schedule(&gscs->pump_transfers);
}
} 说明：
1) 获取下一个transfer，如果还有，则调度gsc3280_spi_pump_transfers()函数准备开始传输。
2) 如果没有transfer需要传输，调用函数gsc3280_spi_giveback(gscs)，说明此时已经处理完成了一个msg。
gsc3280_spi_giveback(gscs)函数如下：
点击(此处)折叠或打开
/* Caller already set message->status; dma and pio
irqs are blocked */
static void gsc3280_spi_giveback(struct gsc3280_spi *gscs)
{
unsigned long flags = 0;
DBG("gsc3280_spi_giveback\n");
//DBG("irq_status = 0x%x\n", readl(gscs->regs + GSC_SPI_ISR));
gsc3280_spi_mask_intr(gscs, GSC_SPI_SR_MASK);
DBG("cs select disable\n");
if (gscs->cur_chip->cs_value == 0) {
gpio_set_value(gscs->cur_chip->pin_cs, 1);
}
else
gpio_set_value(gscs->cur_chip->pin_cs, 0);
gscs->cur_msg->state = NULL;
if (gscs->cur_msg->complete)
gscs->cur_msg->complete(gscs->cur_msg->context);
spin_lock_irqsave(&gscs->slock, flags);
gscs->cur_msg = NULL;
gscs->cur_transfer = NULL;
gscs->prev_chip = gscs->cur_chip;
gscs->cur_chip = NULL;
gscs->busy = 0;
#ifdef CONFIG_SPI_GSC3280_DMA
gscs->dma_mapped = 0;
#endif
spin_unlock_irqrestore(&gscs->slock, flags);
queue_work(gscs->workqueue, &gscs->pump_messages);
}
说明：
1) 首先屏蔽中断。
2) 禁止片选。
3) 设置完成msg。
4) 上锁，初始化SPI总线结构体变量。
5) 调用gsc3280_spi_pump_messages()函数，处理下一个msg。
中断接收数据函数spi_gsc_read(gscs)如下：
点击(此处)折叠或打开
static void gsc3280_reader(struct gsc3280_spi *gscs)
{
u16 rxw = 0;
unsigned long flags = 0;
u32 max = gsc3280_spi_rx_max(gscs);
//DBG("max = %d, gscs->n_bytes = 0x%x", max, gscs->n_bytes);
spin_lock_irqsave(&gscs->slock, flags);
while (max--) {
rxw = readl(gscs->regs + GSC_SPI_DA_S);
DBG("rxw = 0x%x\n", rxw);
if (gscs->n_bytes == 1)
*(u8 *)(gscs->rx) = (u8)rxw;
else
*(u16 *)(gscs->rx) = rxw;
gscs->rx += gscs->n_bytes;
}
spin_unlock_irqrestore(&gscs->slock, flags);
}
static void spi_gsc_read(struct gsc3280_spi *gscs)
{
//DBG("spi_gsc_read\n");
gsc3280_reader(gscs);
if (gscs->rx_end == gscs->rx) {
gsc3280_spi_xfer_done(gscs);
}
}
说明：
1) 首先接收数据，如果接收成功，调用gsc3280_spi_xfer_done(gscs);。
到此，SPI总线驱动就全部讲述完成了，在总线驱动中，使用了queue和tasklet两种机制，queue实现了不同
msg的传输，tasklet实现了msg中不同transfer的传输。
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