S5PV210 ADC驱动分析

　　我这里用的是mini210开发板，在其内核源码中，采用了Linux设备驱动模型中的platform虚拟总线来管理ADC设备。首先看S5PV210提供的ADC驱动接口。在plat-samsung/dev-adc.c中定义了s3c_device_adc，它是一个platform_device结构体，描述adc这个设备。

/* plat-samsung/dev-adc.c */
static struct resource s3c_adc_resource[] = {[0] = {.start = SAMSUNG_PA_ADC,.end   = SAMSUNG_PA_ADC + SZ_256 - 1,.flags = IORESOURCE_MEM,},[1] = {.start = IRQ_TC,.end   = IRQ_TC,.flags = IORESOURCE_IRQ,},[2] = {.start = IRQ_ADC,.end   = IRQ_ADC,.flags = IORESOURCE_IRQ,},
};
struct platform_device s3c_device_adc = {.name        = "samsung-adc",.id        = -1,.num_resources    = ARRAY_SIZE(s3c_adc_resource),.resource    = s3c_adc_resource,
};

　　从中可以看出，s3c_adc_resource中定义了ADC模数转换器所需要的内存地址空间、中断等资源，然后将其作为成员放入到s3c_device_adc结构体中，接下来需要做的是将s3c_device_adc加入到Platform虚拟总线管理的设备链表中去。
　　在s5pv210_map_io函数中，首先将s3c_device_adc的name属性设置成了”s5pv210-adc”。

/* mach-s5pv210/cpu.c */
void __init s5pv210_map_io(void)
{...s3c_adc_setname("s5pv210-adc");...
}
/* re-define device name depending on support. */
static inline void s3c_adc_setname(char *name)
{
**#ifdef CONFIG_SAMSUNG_DEV_ADC**s3c_device_adc.name = name;
**#endif**
}

　　然后，s3c_device_adc结构体指针被添加到mini210_devices[]这个platform_device*结构体指针数组中。

static struct platform_device *mini210_devices[] __initdata = {&s3c_device_adc,...
}

　　最后，通过platform_add_devices(mini210_devices, ARRAY_SIZE(mini210_devices));添加s3c_device_adc到platform虚拟总线管理的设备链表中去。
在Linux的设备驱动模型中，总线、设备和驱动这3个结构体非常重要，总线将设备和驱动绑定。系统每注册一个设备的时候，就会寻找与之匹配的驱动；相反的，系统每注册一个驱动的时候，会寻找与之匹配的设备，匹配工作由总线完成。
　　这里有了ADC的platform device设备，则需要对应的platform driver与其匹配，在plat-samsung/adc.c中，可以找到s3c_adc_init的定义。

static struct platform_device_id s3c_adc_driver_ids[] = {{.name       = "s3c24xx-adc",.driver_data    = TYPE_S3C24XX,}, {.name       = "s3c64xx-adc",.driver_data    = TYPE_S3C64XX,}, {.name       = "s5pv210-adc",.driver_data    = TYPE_S5PV210,},{ }
};
MODULE_DEVICE_TABLE(platform, s3c_adc_driver_ids);static struct platform_driver s3c_adc_driver = {.id_table   = s3c_adc_driver_ids,.driver     = {.name   = "s3c-adc",.owner  = THIS_MODULE,},.probe      = s3c_adc_probe,.remove     = __devexit_p(s3c_adc_remove),.suspend    = s3c_adc_suspend,.resume     = s3c_adc_resume,
};static int __init adc_init(void)
{int ret;ret = platform_driver_register(&s3c_adc_driver);if (ret)printk(KERN_ERR "%s: failed to add adc driver\n", __func__);return ret;
}arch_initcall(adc_init);

　　platform_bus_type总线的math函数依靠platform_device的name属性与platform_driver的driver.name或id_table.name是否一致来完成ADC设备与ADC驱动程序的匹配，匹配成功后，则调用platform driver的probe指向的函数，来对设备进行初始化。
　　s3c_adc_probe()完成了S5PV210的ADC基地址映射、分频值设置、数据位设置等，s3c_adc_remove()函数则实现了相反的功能。

static int s3c_adc_probe(struct platform_device *pdev)
{struct device *dev = &pdev->dev;struct adc_device *adc;struct resource *regs;int ret;unsigned tmp;// 为adc_device结构体分配内存adc = kzalloc(sizeof(struct adc_device), GFP_KERNEL);if (unlikely(adc == NULL)) {    ...     }// 上锁spin_lock_init(&adc->lock);// 设置adc结构体属性值adc->pdev = pdev;adc->prescale = S3C2410_ADCCON_PRSCVL(49);adc->delay = S3C2410_ADCDLY_DELAY(1000);adc->cputype = platform_get_device_id(adc->pdev)->driver_data;adc->irq = platform_get_irq(pdev, 1);           // 获取中断号if (unlikely(adc->irq <= 0)) {  ...     }ret = request_irq(adc->irq, s3c_adc_irq, 0, dev_name(dev), adc);    // 申请中断if (unlikely(ret < 0)) {    ... }adc->clk = clk_get(NULL, "adc");                            // 获取adc设备时钟if (unlikely(IS_ERR(adc->clk))) {   ... }regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);      // 获取资源(相对应寄存器的地址)if (unlikely(!regs)) {  ... }adc->regs = ioremap(regs->start, resource_size(regs));      // 地址映射if (unlikely(!adc->regs)) { ... }clk_enable(adc->clk);                           // 使能时钟tmp = adc->prescale | S3C2410_ADCCON_PRSCEN;if ((adc->cputype == TYPE_S3C64XX) || (adc->cputype == TYPE_S5PV210)){/* Enable 12-bit ADC resolution */tmp |= S3C64XX_ADCCON_RESSEL;}tmp |= S3C2410_ADCCON_STDBM;writel(tmp, adc->regs + S3C2410_ADCCON);        //设置分频值与数据位writel(adc->delay, adc->regs + S3C2410_ADCDLY); //设置AD采集时间platform_set_drvdata(pdev, adc);adc_dev = adc;return 0;err:   ...
}
static int __devexit s3c_adc_remove(struct platform_device *pdev)
{struct adc_device *adc = platform_get_drvdata(pdev);iounmap(adc->regs);free_irq(adc->irq, adc);clk_disable(adc->clk);clk_put(adc->clk);kfree(adc);return 0;
}

　　而s3c_adc_suspend和s3c_adc_resume函数分别用于系统休眠和唤醒时调用。

#ifdef CONFIG_PM
static int s3c_adc_suspend(struct platform_device *pdev, pm_message_t state)
{struct adc_device *adc = platform_get_drvdata(pdev);unsigned long flags;u32 con;spin_lock_irqsave(&adc->lock, flags);con = readl(adc->regs + S3C2410_ADCCON);con |= S3C2410_ADCCON_STDBM;writel(con, adc->regs + S3C2410_ADCCON);disable_irq(adc->irq);spin_unlock_irqrestore(&adc->lock, flags);clk_disable(adc->clk);return 0;
}static int s3c_adc_resume(struct platform_device *pdev)
{struct adc_device *adc = platform_get_drvdata(pdev);unsigned int tmp = 0;clk_enable(adc->clk);enable_irq(adc->irq);tmp = adc->prescale | S3C2410_ADCCON_PRSCEN;/* Enable 12-bit ADC resolution */if ((adc->cputype == TYPE_S3C64XX) || (adc->cputype == TYPE_S5PV210))tmp |= S3C64XX_ADCCON_RESSEL;writel(tmp, adc->regs + S3C2410_ADCCON);writel(adc->delay, adc->regs + S3C2410_ADCDLY);return 0;
}

　　此外，在plat-samsung/adc.c中，还定义了一下其它的函数，用来设置adc通道，读取adc值。

struct s3c_adc_client {struct platform_device  *pdev;struct list_head     pend;wait_queue_head_t   *wait;unsigned int         nr_samples;int          result;unsigned char        is_ts;unsigned char        channel;void    (*select_cb)(struct s3c_adc_client *c, unsigned selected);void    (*convert_cb)(struct s3c_adc_client *c,unsigned val1, unsigned val2,unsigned *samples_left);
};static inline void s3c_adc_convert(struct adc_device *adc)
{unsigned con = readl(adc->regs + S3C2410_ADCCON);con |= S3C2410_ADCCON_ENABLE_START;writel(con, adc->regs + S3C2410_ADCCON);
}static inline void s3c_adc_select(struct adc_device *adc,struct s3c_adc_client *client)
{unsigned con = readl(adc->regs + S3C2410_ADCCON);client->select_cb(client, 1);con &= ~S3C2410_ADCCON_MUXMASK;con &= ~S3C2410_ADCCON_STDBM;con &= ~S3C2410_ADCCON_STARTMASK;con |=  S3C2410_ADCCON_PRSCEN;if (!client->is_ts) {if (adc->cputype == TYPE_S5PV210)writel(S5PV210_ADCCON_SELMUX(client->channel),adc->regs + S5PV210_ADCMUX);elsecon |= S3C2410_ADCCON_SELMUX(client->channel);}writel(con, adc->regs + S3C2410_ADCCON);
}static void s3c_adc_dbgshow(struct adc_device *adc)
{adc_dbg(adc, "CON=%08x, TSC=%08x, DLY=%08x\n",readl(adc->regs + S3C2410_ADCCON),readl(adc->regs + S3C2410_ADCTSC),readl(adc->regs + S3C2410_ADCDLY));
}static void s3c_adc_try(struct adc_device *adc)
{struct s3c_adc_client *next = adc->ts_pend;unsigned int con = readl(adc->regs + S3C2410_ADCCON);if (!next && !list_empty(&adc_pending)) {next = list_first_entry(&adc_pending,struct s3c_adc_client, pend);list_del(&next->pend);} elseadc->ts_pend = NULL;if (next) {adc_dbg(adc, "new client is %p\n", next);adc->cur = next;s3c_adc_select(adc, next);s3c_adc_convert(adc);s3c_adc_dbgshow(adc);} else {con &= ~S3C2410_ADCCON_PRSCEN;con |=  S3C2410_ADCCON_STDBM;writel(con, adc->regs + S3C2410_ADCCON);}
}int s3c_adc_start(struct s3c_adc_client *client,unsigned int channel, unsigned int nr_samples)
{struct adc_device *adc = adc_dev;unsigned long flags;if (!adc) {printk(KERN_ERR "%s: failed to find adc\n", __func__);return -EINVAL;}if (client->is_ts && adc->ts_pend)return -EAGAIN;spin_lock_irqsave(&adc->lock, flags);client->channel = channel;client->nr_samples = nr_samples;if (client->is_ts)adc->ts_pend = client;elselist_add_tail(&client->pend, &adc_pending);if (!adc->cur)s3c_adc_try(adc);spin_unlock_irqrestore(&adc->lock, flags);return 0;
}
EXPORT_SYMBOL_GPL(s3c_adc_start);static void s3c_adc_stop(struct s3c_adc_client *client)
{unsigned long flags;spin_lock_irqsave(&adc_dev->lock, flags);/* We should really check that nothing is in progress. */if (adc_dev->cur == client)adc_dev->cur = NULL;if (adc_dev->ts_pend == client)adc_dev->ts_pend = NULL;else {struct list_head *p, *n;struct s3c_adc_client *tmp;list_for_each_safe(p, n, &adc_pending) {tmp = list_entry(p, struct s3c_adc_client, pend);if (tmp == client)list_del(&tmp->pend);}}if (adc_dev->cur == NULL)s3c_adc_try(adc_dev);spin_unlock_irqrestore(&adc_dev->lock, flags);
}static void s3c_convert_done(struct s3c_adc_client *client,unsigned v, unsigned u, unsigned *left)
{client->result = v;wake_up(client->wait);
}int s3c_adc_read(struct s3c_adc_client *client, unsigned int ch)
{DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wake);int ret;unsigned long flags;spin_lock_irqsave(&adc_dev->lock, flags);client->convert_cb = s3c_convert_done;client->wait = &wake;client->result = -1;spin_unlock_irqrestore(&adc_dev->lock, flags);ret = s3c_adc_start(client, ch, 1);if (ret < 0)goto err;ret = wait_event_timeout(wake, client->result >= 0, HZ / 2);if (client->result < 0) {s3c_adc_stop(client);dev_warn(&adc_dev->pdev->dev, "%s: %p is timed out\n",__func__, client);ret = -ETIMEDOUT;goto err;}client->convert_cb = NULL;return client->result;err:return ret;
}
EXPORT_SYMBOL_GPL(s3c_adc_read);static void s3c_adc_default_select(struct s3c_adc_client *client,unsigned select)
{
}struct s3c_adc_client *s3c_adc_register(struct platform_device *pdev,void (*select)(struct s3c_adc_client *client,unsigned int selected),void (*conv)(struct s3c_adc_client *client,unsigned d0, unsigned d1,unsigned *samples_left),unsigned int is_ts)
{struct s3c_adc_client *client;WARN_ON(!pdev);if (!select)select = s3c_adc_default_select;if (!pdev)return ERR_PTR(-EINVAL);client = kzalloc(sizeof(struct s3c_adc_client), GFP_KERNEL);if (!client) {dev_err(&pdev->dev, "no memory for adc client\n");return ERR_PTR(-ENOMEM);}client->pdev = pdev;client->is_ts = is_ts;client->select_cb = select;client->convert_cb = conv;return client;
}
EXPORT_SYMBOL_GPL(s3c_adc_register);void s3c_adc_release(struct s3c_adc_client *client)
{s3c_adc_stop(client);kfree(client);
}
EXPORT_SYMBOL_GPL(s3c_adc_release);static irqreturn_t s3c_adc_irq(int irq, void *pw)
{struct adc_device *adc = pw;struct s3c_adc_client *client = adc->cur;unsigned data0, data1;if (!client) {dev_warn(&adc->pdev->dev, "%s: no adc pending\n", __func__);goto exit;}data0 = readl(adc->regs + S3C2410_ADCDAT0);data1 = readl(adc->regs + S3C2410_ADCDAT1);adc_dbg(adc, "read %d: 0x%04x, 0x%04x\n", client->nr_samples, data0, data1);if (client->nr_samples > 0)client->nr_samples--;if ((adc->cputype == TYPE_S3C64XX) || (adc->cputype == TYPE_S5PV210)) {/* S3C64XX ADC resolution is 12-bit */data0 &= 0xfff;data1 &= 0xfff;} else {data0 &= 0x3ff;data1 &= 0x3ff;}if (client->convert_cb)(client->convert_cb)(client, data0, data1, &client->nr_samples);if (client->nr_samples > 0) {/* fire another conversion for this */client->select_cb(client, 1);s3c_adc_convert(adc);} else {spin_lock(&adc->lock);(client->select_cb)(client, 0);adc->cur = NULL;s3c_adc_try(adc);spin_unlock(&adc->lock);}exit:if ((adc->cputype == TYPE_S3C64XX) || (adc->cputype == TYPE_S5PV210)) {/* Clear ADC interrupt */writel(0, adc->regs + S3C64XX_ADCCLRINT);}return IRQ_HANDLED;
}

　　实际使用中，以drivers/char/mini210_adc.c文件为例，如下面代码所示，先通过s3c_adc_register()函数申请一个s3c_adc_client结构体变量指针，然后通过ret = s3c_adc_read(adcdev.client, adcdev.channel);读相应通道的adc值即可。

typedef struct {struct mutex lock;struct s3c_adc_client *client;int channel;
} ADC_DEV;static ADC_DEV adcdev;
...
adcdev.client = s3c_adc_register(dev, NULL, NULL, 0);
...
ret = mutex_lock_interruptible(&adcdev.lock);
if(ret<0){...}
ret = s3c_adc_read(adcdev.client, adcdev.channel);
mutex_unlock(&adcdev.lock);

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