linux驱动开发之spi-omap-100k.c源码分析

代码分析

对于linux的驱动代码来说，我们要从后往前分析：

/** OMAP7xx SPI 100k controller driver* Author: Fabrice Crohas <fcrohas@gmail.com>* from original omap1_mcspi driver** Copyright (C) 2005, 2006 Nokia Corporation* Author:      Samuel Ortiz <samuel.ortiz@nokia.com> and*              Juha Yrj�l� <juha.yrjola@nokia.com>** This program is free software; you can redistribute it and/or modify* it under the terms of the GNU General Public License as published by* the Free Software Foundation; either version 2 of the License, or* (at your option) any later version.** This program is distributed in the hope that it will be useful,* but WITHOUT ANY WARRANTY; without even the implied warranty of* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the* GNU General Public License for more details.** You should have received a copy of the GNU General Public License* along with this program; if not, write to the Free Software* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA**/
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/delay.h>
#include <linux/platform_device.h>
#include <linux/err.h>
#include <linux/clk.h>
#include <linux/io.h>
#include <linux/gpio.h>
#include <linux/slab.h>#include <linux/spi/spi.h>#include <plat/clock.h>#define OMAP1_SPI100K_MAX_FREQ          48000000#define ICR_SPITAS      (OMAP7XX_ICR_BASE + 0x12)#define SPI_SETUP1      0x00
#define SPI_SETUP2      0x02
#define SPI_CTRL        0x04
#define SPI_STATUS      0x06
#define SPI_TX_LSB      0x08
#define SPI_TX_MSB      0x0a
#define SPI_RX_LSB      0x0c
#define SPI_RX_MSB      0x0e#define SPI_SETUP1_INT_READ_ENABLE      (1UL << 5)
#define SPI_SETUP1_INT_WRITE_ENABLE     (1UL << 4)
#define SPI_SETUP1_CLOCK_DIVISOR(x)     ((x) << 1)
#define SPI_SETUP1_CLOCK_ENABLE         (1UL << 0)#define SPI_SETUP2_ACTIVE_EDGE_FALLING  (0UL << 0)
#define SPI_SETUP2_ACTIVE_EDGE_RISING   (1UL << 0)
#define SPI_SETUP2_NEGATIVE_LEVEL       (0UL << 5)
#define SPI_SETUP2_POSITIVE_LEVEL       (1UL << 5)
#define SPI_SETUP2_LEVEL_TRIGGER        (0UL << 10)
#define SPI_SETUP2_EDGE_TRIGGER         (1UL << 10)#define SPI_CTRL_SEN(x)                 ((x) << 7)
#define SPI_CTRL_WORD_SIZE(x)           (((x) - 1) << 2)
#define SPI_CTRL_WR                     (1UL << 1)
#define SPI_CTRL_RD                     (1UL << 0)#define SPI_STATUS_WE                   (1UL << 1)
#define SPI_STATUS_RD                   (1UL << 0)#define WRITE 0
#define READ  1/* use PIO for small transfers, avoiding DMA setup/teardown overhead and* cache operations; better heuristics consider wordsize and bitrate.*/
#define DMA_MIN_BYTES                   8#define SPI_RUNNING    0
#define SPI_SHUTDOWN    1struct omap1_spi100k {struct work_struct      work;/* lock protects queue and registers */spinlock_t              lock;struct list_head        msg_queue;struct spi_master       *master;struct clk              *ick;struct clk              *fck;/* Virtual base address of the controller */void __iomem            *base;/* State of the SPI */unsigned int        state;
};struct omap1_spi100k_cs {void __iomem            *base;int                     word_len;
};static struct workqueue_struct *omap1_spi100k_wq;#define MOD_REG_BIT(val, mask, set) do { \if (set) \val |= mask; \else \val &= ~mask; \
} while (0)static void spi100k_enable_clock(struct spi_master *master)
{unsigned int val;struct omap1_spi100k *spi100k = spi_master_get_devdata(master);/* enable SPI */val = readw(spi100k->base + SPI_SETUP1);val |= SPI_SETUP1_CLOCK_ENABLE;writew(val, spi100k->base + SPI_SETUP1);
}static void spi100k_disable_clock(struct spi_master *master)
{unsigned int val;struct omap1_spi100k *spi100k = spi_master_get_devdata(master);/* disable SPI */val = readw(spi100k->base + SPI_SETUP1);val &= ~SPI_SETUP1_CLOCK_ENABLE;writew(val, spi100k->base + SPI_SETUP1);
}static void spi100k_write_data(struct spi_master *master, int len, int data)
{struct omap1_spi100k *spi100k = spi_master_get_devdata(master);/* write 16-bit word, shifting 8-bit data if necessary */if (len <= 8) {data <<= 8;len = 16;}spi100k_enable_clock(master);writew( data , spi100k->base + SPI_TX_MSB);writew(SPI_CTRL_SEN(0) |SPI_CTRL_WORD_SIZE(len) |SPI_CTRL_WR,spi100k->base + SPI_CTRL);/* Wait for bit ack send change */while((readw(spi100k->base + SPI_STATUS) & SPI_STATUS_WE) != SPI_STATUS_WE);udelay(1000);spi100k_disable_clock(master);
}static int spi100k_read_data(struct spi_master *master, int len)
{int dataH,dataL;struct omap1_spi100k *spi100k = spi_master_get_devdata(master);/* Always do at least 16 bits */if (len <= 8)len = 16;spi100k_enable_clock(master);writew(SPI_CTRL_SEN(0) |SPI_CTRL_WORD_SIZE(len) |SPI_CTRL_RD,spi100k->base + SPI_CTRL);while((readw(spi100k->base + SPI_STATUS) & SPI_STATUS_RD) != SPI_STATUS_RD);udelay(1000);dataL = readw(spi100k->base + SPI_RX_LSB);dataH = readw(spi100k->base + SPI_RX_MSB);spi100k_disable_clock(master);return dataL;
}static void spi100k_open(struct spi_master *master)
{/* get control of SPI */struct omap1_spi100k *spi100k = spi_master_get_devdata(master);writew(SPI_SETUP1_INT_READ_ENABLE |SPI_SETUP1_INT_WRITE_ENABLE |SPI_SETUP1_CLOCK_DIVISOR(0), spi100k->base + SPI_SETUP1);/* configure clock and interrupts */writew(SPI_SETUP2_ACTIVE_EDGE_FALLING |SPI_SETUP2_NEGATIVE_LEVEL |SPI_SETUP2_LEVEL_TRIGGER, spi100k->base + SPI_SETUP2);
}static void omap1_spi100k_force_cs(struct omap1_spi100k *spi100k, int enable)
{if (enable)writew(0x05fc, spi100k->base + SPI_CTRL);elsewritew(0x05fd, spi100k->base + SPI_CTRL);
}static unsigned
omap1_spi100k_txrx_pio(struct spi_device *spi, struct spi_transfer *xfer)
{struct omap1_spi100k    *spi100k;struct omap1_spi100k_cs *cs = spi->controller_state;unsigned int            count, c;int                     word_len;spi100k = spi_master_get_devdata(spi->master);count = xfer->len;c = count;word_len = cs->word_len;if (word_len <= 8) {u8              *rx;const u8        *tx;rx = xfer->rx_buf;tx = xfer->tx_buf;do {c-=1;if (xfer->tx_buf != NULL)spi100k_write_data(spi->master, word_len, *tx++);if (xfer->rx_buf != NULL)*rx++ = spi100k_read_data(spi->master, word_len);} while(c);} else if (word_len <= 16) {u16             *rx;const u16       *tx;rx = xfer->rx_buf;tx = xfer->tx_buf;do {c-=2;if (xfer->tx_buf != NULL)spi100k_write_data(spi->master,word_len, *tx++);if (xfer->rx_buf != NULL)*rx++ = spi100k_read_data(spi->master,word_len);} while(c);} else if (word_len <= 32) {u32             *rx;const u32       *tx;rx = xfer->rx_buf;tx = xfer->tx_buf;do {c-=4;if (xfer->tx_buf != NULL)spi100k_write_data(spi->master,word_len, *tx);if (xfer->rx_buf != NULL)*rx = spi100k_read_data(spi->master,word_len);} while(c);}return count - c;
}/* called only when no transfer is active to this device */
static int omap1_spi100k_setup_transfer(struct spi_device *spi,struct spi_transfer *t)
{struct omap1_spi100k *spi100k = spi_master_get_devdata(spi->master);struct omap1_spi100k_cs *cs = spi->controller_state;u8 word_len = spi->bits_per_word;if (t != NULL && t->bits_per_word)word_len = t->bits_per_word;if (!word_len)word_len = 8;if (spi->bits_per_word > 32)return -EINVAL;cs->word_len = word_len;/* SPI init before transfer */writew(0x3e , spi100k->base + SPI_SETUP1);writew(0x00 , spi100k->base + SPI_STATUS);writew(0x3e , spi100k->base + SPI_CTRL);return 0;
}/* the spi->mode bits understood by this driver: */
#define MODEBITS (SPI_CPOL | SPI_CPHA | SPI_CS_HIGH)static int omap1_spi100k_setup(struct spi_device *spi)
{int                     ret;struct omap1_spi100k    *spi100k;struct omap1_spi100k_cs *cs = spi->controller_state;if (spi->bits_per_word < 4 || spi->bits_per_word > 32) {dev_dbg(&spi->dev, "setup: unsupported %d bit words\n",spi->bits_per_word);return -EINVAL;}spi100k = spi_master_get_devdata(spi->master);if (!cs) {cs = kzalloc(sizeof *cs, GFP_KERNEL);if (!cs)return -ENOMEM;cs->base = spi100k->base + spi->chip_select * 0x14;spi->controller_state = cs;}spi100k_open(spi->master);clk_enable(spi100k->ick);clk_enable(spi100k->fck);ret = omap1_spi100k_setup_transfer(spi, NULL);clk_disable(spi100k->ick);clk_disable(spi100k->fck);return ret;
}
// 信息传输的工作就在这个函数执行啦，这里每次传输一次，就使能一次
static void omap1_spi100k_work(struct work_struct *work)
{struct omap1_spi100k    *spi100k;int status = 0;spi100k = container_of(work, struct omap1_spi100k, work);spin_lock_irq(&spi100k->lock);clk_enable(spi100k->ick);clk_enable(spi100k->fck);/* We only enable one channel at a time -- the one whose message is* at the head of the queue -- although this controller would gladly* arbitrate among multiple channels.  This corresponds to "single* channel" master mode.  As a side effect, we need to manage the* chipselect with the FORCE bit ... CS != channel enable.*/while (!list_empty(&spi100k->msg_queue)) {struct spi_message              *m;struct spi_device               *spi;struct spi_transfer             *t = NULL;int                             cs_active = 0;struct omap1_spi100k_cs         *cs;int                             par_override = 0;m = container_of(spi100k->msg_queue.next, struct spi_message,queue);list_del_init(&m->queue);spin_unlock_irq(&spi100k->lock);spi = m->spi;cs = spi->controller_state;list_for_each_entry(t, &m->transfers, transfer_list) {if (t->tx_buf == NULL && t->rx_buf == NULL && t->len) {status = -EINVAL;break;}if (par_override || t->speed_hz || t->bits_per_word) {par_override = 1;status = omap1_spi100k_setup_transfer(spi, t);if (status < 0)break;if (!t->speed_hz && !t->bits_per_word)par_override = 0;}if (!cs_active) {omap1_spi100k_force_cs(spi100k, 1);cs_active = 1;}if (t->len) {unsigned count;count = omap1_spi100k_txrx_pio(spi, t);m->actual_length += count;if (count != t->len) {status = -EIO;break;}}if (t->delay_usecs)udelay(t->delay_usecs);/* ignore the "leave it on after last xfer" hint */if (t->cs_change) {omap1_spi100k_force_cs(spi100k, 0);cs_active = 0;}}/* Restore defaults if they were overriden */if (par_override) {par_override = 0;status = omap1_spi100k_setup_transfer(spi, NULL);}if (cs_active)omap1_spi100k_force_cs(spi100k, 0);m->status = status;m->complete(m->context);spin_lock_irq(&spi100k->lock);}clk_disable(spi100k->ick);clk_disable(spi100k->fck);spin_unlock_irq(&spi100k->lock);if (status < 0)printk(KERN_WARNING "spi transfer failed with %d\n", status);
}// 这个函数就是在驱动设备已经绑定好后开始进行传输使用的函数，下面我们来分析。
// 从函数参数来看，有2个参数，一个是设备参数指针，另一个是信息流指针，从这里我们可以
// 看出调用此函数是为了向spi这个设备传送m这个信息流。
static int omap1_spi100k_transfer(struct spi_device *spi, struct spi_message *m)
{struct omap1_spi100k    *spi100k;unsigned long           flags;struct spi_transfer     *t;m->actual_length = 0;m->status = -EINPROGRESS;// 从spi主驱动获取设备数据spi100k = spi_master_get_devdata(spi->master);/* Don't accept new work if we're shutting down */// 这个人家也说了，在进行退出模块的过程的中如果有传输的任务的话，我们// 就不再传输了，直接退出。if (spi100k->state == SPI_SHUTDOWN)return -ESHUTDOWN;/* reject invalid messages and transfers */// 这段代码的意思呢就是当该设备没有完整的准备传输数据时，就不再进行传输了。if (list_empty(&m->transfers) || !m->complete)return -EINVAL;// 这段代码就是传输代码的检测步骤，目的是为了检测当前通信频率是否符合要求。list_for_each_entry(t, &m->transfers, transfer_list) {const void      *tx_buf = t->tx_buf;void            *rx_buf = t->rx_buf;unsigned        len = t->len;if (t->speed_hz > OMAP1_SPI100K_MAX_FREQ|| (len && !(rx_buf || tx_buf))|| (t->bits_per_word &&(  t->bits_per_word < 4|| t->bits_per_word > 32))) {dev_dbg(&spi->dev, "transfer: %d Hz, %d %s%s, %d bpw\n",t->speed_hz,len,tx_buf ? "tx" : "",rx_buf ? "rx" : "",t->bits_per_word);return -EINVAL;}if (t->speed_hz && t->speed_hz < OMAP1_SPI100K_MAX_FREQ/(1<<16)) {dev_dbg(&spi->dev, "%d Hz max exceeds %d\n",t->speed_hz,OMAP1_SPI100K_MAX_FREQ/(1<<16));return -EINVAL;}}// 这段代码就是将m的信息流加到该设备的传输信息流链表中，// 然后传输的工作在另一个线程中omap1_spi100k_wq执行。spin_lock_irqsave(&spi100k->lock, flags);list_add_tail(&m->queue, &spi100k->msg_queue);queue_work(omap1_spi100k_wq, &spi100k->work);spin_unlock_irqrestore(&spi100k->lock, flags);return 0;
}static int __init omap1_spi100k_reset(struct omap1_spi100k *spi100k)
{return 0;
}// 线程的探测函数，当探测成后即刻进行初始化该设备操作。
static int __devinit omap1_spi100k_probe(struct platform_device *pdev)
{struct spi_master       *master;struct omap1_spi100k    *spi100k;int                     status = 0;// 设备的id不能为0，要么为-1，要么为其他正数，表示同一类设备的唯一性或枚举性。if (!pdev->id)return -EINVAL;// 给一个平台设备，然后申请一个spi的驱动框架。master = spi_alloc_master(&pdev->dev, sizeof *spi100k);if (master == NULL) {dev_dbg(&pdev->dev, "master allocation failed\n");return -ENOMEM;}if (pdev->id != -1)master->bus_num = pdev->id;// 填充刚申请的spi驱动框架master->setup = omap1_spi100k_setup;master->transfer = omap1_spi100k_transfer;master->cleanup = NULL;master->num_chipselect = 2;master->mode_bits = MODEBITS;// 将该驱动框架的结构体对象设置到该设备中，用与内核的使用dev_set_drvdata(&pdev->dev, master);// 从spi的驱动框架中获取设备数据，这个设备数据就是该模块的中定义的结构体中的数据spi100k = spi_master_get_devdata(master);spi100k->master = master;/** The memory region base address is taken as the platform_data.* You should allocate this with ioremap() before initializing* the SPI.*/// 这个平台数据就是设备中本身携带的数据了，一般这些信息可以通过设备树传输spi100k->base = (void __iomem *) pdev->dev.platform_data;INIT_WORK(&spi100k->work, omap1_spi100k_work);spin_lock_init(&spi100k->lock);INIT_LIST_HEAD(&spi100k->msg_queue);// 获取时钟源spi100k->ick = clk_get(&pdev->dev, "ick");if (IS_ERR(spi100k->ick)) {dev_dbg(&pdev->dev, "can't get spi100k_ick\n");status = PTR_ERR(spi100k->ick);goto err1;}spi100k->fck = clk_get(&pdev->dev, "fck");if (IS_ERR(spi100k->fck)) {dev_dbg(&pdev->dev, "can't get spi100k_fck\n");status = PTR_ERR(spi100k->fck);goto err2;}// 复位该设备，一般在使用该设备之前都要进行复位一次。if (omap1_spi100k_reset(spi100k) < 0)goto err3;// 开始注册该设备驱动status = spi_register_master(master);if (status < 0)goto err3;spi100k->state = SPI_RUNNING;return status;err3:clk_put(spi100k->fck);
err2:clk_put(spi100k->ick);
err1:spi_master_put(master);return status;
}// 当该模块退出时，我们会调用这个函数，进行移除该模块原来在系统中占用的空间
// 下面我们来分析这个移除模块的移除步骤。
static int __exit omap1_spi100k_remove(struct platform_device *pdev)
{struct spi_master       *master;struct omap1_spi100k    *spi100k;struct resource         *r;unsigned       limit = 500;unsigned long      flags;int           status = 0;// 从设备获取我们的驱动信息master = dev_get_drvdata(&pdev->dev);// 从驱动信息获取我们的设备数据spi100k = spi_master_get_devdata(master);// 自旋锁加锁，并关中断，进行一些短的不被除此之外鹅任何进程打扰到的代码片段spin_lock_irqsave(&spi100k->lock, flags);// 改变该设备的标志位信息，使其为关闭状态spi100k->state = SPI_SHUTDOWN;// 这段代码的意思是尽可能的的等待该设备的还存在的信息进行处理完成，// 因为马上要关闭模块了。while (!list_empty(&spi100k->msg_queue) && limit--) {spin_unlock_irqrestore(&spi100k->lock, flags);msleep(10);spin_lock_irqsave(&spi100k->lock, flags);}// 这个就是判断设备的信息队列中是否还有数据，如果进行了之前的操作仍然不能处理完设备// 中的信息队列，那么就显示设备状态为忙状态，不再进行此次的退出操作。if (!list_empty(&spi100k->msg_queue))status = -EBUSY;// 释放自旋锁，恢复中断，目的是为了保护这加锁期间的代码spin_unlock_irqrestore(&spi100k->lock, flags);if (status != 0)return status;// 这里就是释放用于spi通信使用的时钟源，注意// clk_put函数不能在中断上下文中使用，具体为什么，可以看源码clk_put(spi100k->fck);clk_put(spi100k->ick);// 这个时候应该对资源进行一些处理的，但这里并没有处理，只是获取而已。r = platform_get_resource(pdev, IORESOURCE_MEM, 0);// 调用该函数注销这个spi主设备的驱动。spi_unregister_master(master);return 0;
}// 我们的驱动结构体，我们需要在这个结构体中填充关于该驱动的写必要的信息。
// 一般情况下，我们至少要填充平台驱动下的设备驱动变量中的名称name和所属者owener，
// 这是设备驱动中需要的最小信息，之后我们要填充平台驱动下的移除函数remove，填写
// 这个函数为了卸载该模块使用的，至于平台驱动下的探测函数会在初始话函数中进行填充。
static struct platform_driver omap1_spi100k_driver = {.driver = {.name        = "omap1_spi100k",.owner     = THIS_MODULE,},.remove        = __exit_p(omap1_spi100k_remove),
};static int __init omap1_spi100k_init(void)
{// create a single thread work queue,// we must free the work queue when exit the driver.// the purpose of creating a single thread is// to excute the @spi100k->work function.omap1_spi100k_wq = create_singlethread_workqueue(omap1_spi100k_driver.driver.name);if (omap1_spi100k_wq == NULL)return -1;// 该处初始化函数调用平台驱动探测函数，会传入2个参数，一个是我们该模块的驱动信息，// 另一个是该模块的探测函数。执行这个接口的目的是为了将该模块的驱动信息与已经在系统// 注册的设备信息进行绑定，然后在该模块探测函数中初始化一些该模块必要// 初始化步骤，用来支持该模块的工作。该模块就是通过spi进行通信的。至于系统怎么// 绑定设备与驱动的，感兴趣的可以分析下源码，这里不再分析。return platform_driver_probe(&omap1_spi100k_driver, omap1_spi100k_probe);
}static void __exit omap1_spi100k_exit(void)
{// 平台驱动注销函数接口，为什么会有这个接口呢？就是因为在该模块初始化过程中，// 调用了平台驱动注册函数，其函数内部因为有申请堆空间或者加载链表信息等操作，// 所以，在退出的时候，一定要归还这些系统中的位置。platform_driver_unregister(&omap1_spi100k_driver);// 一样的解释，前面初始化申请了一个单线程的工作队列用于处理该驱动的通信工作，// 当退出时，一定要把这个申请的工作队列释放掉，为系统腾出空间。destroy_workqueue(omap1_spi100k_wq);
}// 模块的加载入口，当初始化该模块或者注册该模块时，系统会执行omap1_spi100k_init该
// 函数，进行注册一些驱动运行需要的信息，并且与设备的信息进行绑定，
// 形成完成的驱动的初始化流程.
module_init(omap1_spi100k_init);// 模块的卸载入口，当不再使用模块时，内核代码会调用该接口并执行omap1_spi100k_exit
// 函数，释放一些申请的内存空间，然后从运行的系统中删除自己的一些信息。
module_exit(omap1_spi100k_exit);// 模块的作者信息，和一些描述信息。让人们知道该模块的基本信息
MODULE_DESCRIPTION("OMAP7xx SPI 100k controller driver");
MODULE_AUTHOR("Fabrice Crohas <fcrohas@gmail.com>");// 模块遵循的许可证，对于我们驱动开发来说，一般写成GPL就可以
MODULE_LICENSE("GPL");

总结

从上面的代码分析来看，驱动最关键的部分就是探测函数和工作函数了，它们一个负责绑定初始化设备驱动，另一个负责驱动通信的主体工作，其他函数就是围绕它们来展开的。

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