linux驱动spi程序深层分析

err = PTR_ERR(hw->clk);
goto err_no_clk;
}
/* for the moment, permanently enable the clock */
clk_enable(hw->clk);
err = spi_bitbang_start(&hw->bitbang);
if (err) {
dev_err(&pdev->dev, "Failed to register SPI master\n");
goto err_register;
dev_dbg(hw->dev, "bitbang at %p\n", &hw->bitbang);
/* find and map our resources */
/* 申请spi所用到的资源：io、irq、时钟等 */
res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
bi = &hw->pdata->board_info[0];
for (i = 0; i < hw->pdata->board_size; i++, bi++) {
dev_info(hw->dev, "registering %s\n", bi->modalias);
writeb(SPCON_DEFAULT, hw->regs + S3C2410_SPCON);
/* add by lfc */
s3c2410_gpio_setpin(S3C2410_GPE13, 0);
s3c2410_gpio_setpin(S3C2410_GPE12, 0);
{
struct s3c24xx_spi *hw;
struct spi_master *master;
struct spi_board_info *bi;
struct resource *res;
int err = 0;
2.6.18内核下已经添加了完整的spi子系统了，参考mtd的分析，将从下到上层，再从上到下层的对其进行分析。
以下先从下到上的进行分析：
driver/spi下有两个底层相关的spi驱动程序：
spi_s3c24xx.c和spi_s3c24xx_gpio.c
其中spi_s3c24xx.c是基于s3c24xx下相应的spi接口的驱动程序，spi_s3c24xx_gpio.c允许用户指定3个gpio口，分别充当spi_clk、spi_mosi和spi_miso接口，模拟标准的spi总线。
hw->bitbang.chipselect = s3c24xx_spi_chipsel;
hw->bitbang.txrx_bufs = s3c24xx_spi_txrx;
hw->bitbang.master->setup = s3c24xx_spi_setup;
}
hw->ioarea = request_mem_region(res->start, (res->end - res->start)+1,
pdev->name);
if (hw->ioarea == NULL) {
goto err_no_irq;
}
hw->clk = clk_get(&pdev->dev, "spi");
if (IS_ERR(hw->clk)) {
dev_err(&pdev->dev, "No clock for device\n");
s3c2410_gpio_cfgpin(hw->pdata->pin_cs, S3C2410_GPIO_OUTPUT);
}
/* register our spi controller */
/* 最终通过调用spi_register_master来注册spi控制器(驱动) */
if (res == NULL) {
dev_err(&pdev->dev, "Cannot get IORESOURCE_MEM\n");
err = -ENOENT;
goto err_no_iores;
*/
master = spi_alloc_master(&pdev->dev, sizeof(struct s3c24xx_spi));
if (master == NULL) {
dev_err(&pdev->dev, "No memory for spi_master\n");
}
dev_dbg(hw->dev, "shutdown=%d\n", hw->bitbang.shutdown);
/* register all the devices associated */
/* 注册所用使用本spi驱动的设备 */
dev_err(&pdev->dev, "Cannot reserve region\n");
err = -ENXIO;
Hale Waihona Puke oto err_no_iores;
}
hw->regs = ioremap(res->start, (res->end - res->start)+1);
/* program defaults into the registers */
/* 初始化spi相关的寄存器 */
writeb(0xff, hw->regs + S3C2410_SPPRE);
writeb(SPPIN_DEFAULT, hw->regs + S3C2410_SPPIN);
err = -ENOMEM;
goto err_nomem;
}
/* 填充struct spi_master结构 */
hw = spi_master_get_devdata(master);
s3c2410自带了两个spi接口(spi0和spi1)，在此我只研究基于s3c2410下spi接口的驱动程序spi_s3c24xx.c。
首先从spi驱动的检测函数进行分析：
static int s3c24xx_spi_probe(struct platform_device *pdev)
s3c2410_gpio_cfgpin(S3C2410_GPE13, S3C2410_GPE13_SPICLK0);
s3c2410_gpio_cfgpin(S3C2410_GPE12, S3C2410_GPE12_SPIMOSI0);
s3c2410_gpio_cfgpin(S3C2410_GPE11, S3C2410_GPE11_SPIMISO0);
if (hw->regs == NULL) {
dev_err(&pdev->dev, "Cannot map IO\n");
err = -ENXIO;
goto err_no_iomap;
/* 填充hw->bitbang结构(hw->bitbang结构充当一个中间层，相当与input system的input_handle struct) */
hw->bitbang.master = hw->master;
hw->bitbang.setup_transfer = s3c24xx_spi_setupxfer;
if (hw->pdata == NULL) {
dev_err(&pdev->dev, "No platform data supplied\n");
err = -ENOENT;
goto err_no_pdata;
}
hw->irq = platform_get_irq(pdev, 0);
if (hw->irq < 0) {
dev_err(&pdev->dev, "No IRQ specified\n");
err = -ENOENT;
goto err_no_irq;
}
err = request_irq(hw->irq, s3c24xx_spi_irq, 0, pdev->name, hw);
if (err) {
dev_err(&pdev->dev, "Cannot claim IRQ\n");
/* end add */
/* setup any gpio we can */
/* 片选 */
if (!hw->pdata->set_cs) {
s3c2410_gpio_setpin(hw->pdata->pin_cs, 1);
bi->controller_data = hw;
int i;
/* pi_alloc_master函数申请了struct spi_master+struct s3c24xx_spi大小的数据，
* spi_master_get_devdata和pi_master_get分别取出struct s3c24xx_spi和struct spi_master结构指针
memset(hw, 0, sizeof(struct s3c24xx_spi));
hw->master = spi_master_get(master);
hw->pdata = pdev->dev.platform_data;
hw->dev = &pdev->dev;
}
platform_set_drvdata(pdev, hw);//dev_set_drvdata(&pdev->dev, hw)
init_completion(&hw->done);
/* setup the state for the bitbang driver */