Linux-2.6.32.2下为ST16C554移植驱动的经历

谁借莪１个温暖的怀抱￠ 2022-08-18 11:45 197阅读 0赞

一、Linux 驱动的基本理论

理解linux驱动，最重要的是要区分device和driver这两个概念,要搞清device和driver之间的联系。 device 描述了某个设备所占用的硬件资源（地址、中断），可以理解为硬件方面描述。而driver则是描述了使用和操作该设备的方法、流程、逻辑，可以理解为软件方面的描述。这二者之间的对应联系是一个设备名。

我们来看一下两个结构体的定义：

struct platform\_device \{

const char\* name; /\* 连接device和driver的名字，系统内唯一！\*/

int id;

struct device dev;

u32  num\_resources;

struct resource \* resource;

struct platform\_device\_id \* id\_entry;

struct pdev\_archdata archdata;

\};

在arch/arm/mach-s3c2440/mach-mini2440.c中初始化

struct device \{

struct device          \*parent;

struct device\_private      \*p;

struct kobject kobj;

const char              \*init\_name; /\* initial name of the device \*/

struct device\_type   \*type;

struct semaphore    sem; /\* semaphore to synchronize calls to its driver. \*/

struct bus\_type       \*bus;              /\* type of bus device is on \*/

struct device\_driver \*driver;  /\* which driver has allocated this device \*/

void        \*platform\_data;      /\* Platform specific data, device core doesn't touch it \*/

struct dev\_pm\_info power;

\#ifdef CONFIG\_NUMA

int          numa\_node;    /\* NUMA node this device is close to \*/

\#endif

u64         \*dma\_mask;   /\* dma mask (if dma'able device) \*/

u64         coherent\_dma\_mask;

struct device\_dma\_parameters \*dma\_parms;

struct list\_head       dma\_pools;     /\* dma pools (if dma'ble) \*/

struct dma\_coherent\_mem     \*dma\_mem; /\* internal for coherent mem override \*/

struct dev\_archdata archdata; /\* arch specific additions \*/

dev\_t      devt;              /\* dev\_t, creates the sysfs "dev" \*/

spinlock\_t              devres\_lock;

struct list\_head       devres\_head;

struct klist\_node     knode\_class;

struct class             \*class;

const struct attribute\_group \*\*groups;  /\* optional groups \*/

void (\*release)(struct device \*dev);

\};

struct platform\_driver \{

int (\*probe)(struct platform\_device \*);

int (\*remove)(struct platform\_device \*);

void (\*shutdown)(struct platform\_device \*);

int (\*suspend)(struct platform\_device \*, pm\_message\_t state);

int (\*resume)(struct platform\_device \*);

struct device\_driver driver;

struct platform\_device\_id \*id\_table;

\};

在drivers/serial/8250.c中初始化

struct device\_driver \{

const char \*name;  /\* 连接device和driver的名字，系统内唯一！\*/

struct bus\_type \*bus;

struct module  \*owner;

const char \*mod\_name;  /\* used for built-in modules \*/

bool suppress\_bind\_attrs;      /\* disables bind/unbind via sysfs \*/

int (\*probe) (struct device \*dev);

int (\*remove) (struct device \*dev);

void (\*shutdown) (struct device \*dev);

int (\*suspend) (struct device \*dev, pm\_message\_t state);

int (\*resume) (struct device \*dev);

const struct attribute\_group \*\*groups;

const struct dev\_pm\_ops \*pm;

struct driver\_private \*p;

\};

二、ST16C554

st16c554是一款集成了4路标准异步串行收发器的串口扩展芯片，也就是通常所说的16c550（也同8250）适应串口。可以将其看成是简单封装了4个16c550的芯片。它的操作方法和寄存器用法与8250完全相同，因此我们可以用linux内经典的8250驱动来驱动st16c554。

三、移植过程

硬件平台：mini2440    系统：linux-2.6.32.2

红色部分为添加的语句。

1.        修改arch/arm/mach-s3c2440/mach-mini2440.c

*添加头文件*

\#ifdef CONFIG\_SERIAL\_8250\_MINI2440\_ST16C554

\#include

\#endif

*初始化st16c554的platform\_device数据结构*

/\* STC16c554 Extend Quad Uarts \*/

\#define PORT(\_base,\_irq)                           \\

\{ //ARM体系结构中将IO和MEMORY统一编址，

//因此这里使用的是Memory地址

.mapbase = (unsigned long)\_base,    \\

.irq                = \_irq,                  \\

.uartclk          = 1843200,            \\

.iotype           = UPIO\_MEM32,         \\

.flags             = (UPF\_BOOT\_AUTOCONF | UPF\_IOREMAP),      \\

.regshift         = 0, \\

static struct plat\_serial8250\_port mini2440\_st16c554\_8250\_data\[\] = \{

PORT(S3C2410\_CS1 + 0x0, IRQ\_EINT0),

PORT(S3C2410\_CS2 + 0x0, IRQ\_EINT1),

PORT(S3C2410\_CS3 + 0x0, IRQ\_EINT2),

PORT(S3C2410\_CS5 + 0x0, IRQ\_EINT3),

\{ \},

\};

static struct platform\_device mini2440\_device\_st16c554 = \{

.name             = "serial8250",

.id                 = PLAT8250\_DEV\_EXAR\_ST16C554,

.dev               = \{

.platform\_data       = &mini2440\_st16c554\_8250\_data,

\},

\};

*将st16c554对应的platform\_device数据结构体添加到mini2440对应的platform\_device数据结构体中。*

/\* devices we initialise \*/

static struct platform\_device \*mini2440\_devices\[\] \_\_initdata = \{

&s3c\_device\_usb,

&s3c\_device\_rtc,

&s3c\_device\_lcd,

&s3c\_device\_wdt,

&s3c\_device\_i2c0,

&s3c\_device\_iis,

&mini2440\_device\_eth,

//\#ifdef CONFIG\_SERIAL\_8250\_MINI2440\_ST16C554

&mini2440\_device\_st16c554,

//\#endif

&s3c24xx\_uda134x,

&s3c\_device\_nand,

&s3c\_device\_sdi,

&s3c\_device\_usbgadget,

\};

2．修改 drivers/serial/8250.c

*       添加头文件*

\#ifdef CONFIG\_SERIAL\_8250\_MINI2440\_ST16C554

\#include

\#endif

*修改S3C2440 四个Bank使用的的 bus width为8位，以及设定这四个Bank的总线 timing。*

static int \_\_init serial8250\_init(void)

int ret;

if (nr\_uarts > UART\_NR)

nr\_uarts = UART\_NR;

printk(KERN\_INFO "Serial: 8250/16550 driver, "

"%d ports, IRQ sharing %sabled\\n", nr\_uarts,

share\_irqs ? "en" : "dis");

\#ifdef CONFIG\_SERIAL\_8250\_MINI2440\_ST16C554

/\* Set the 8bit bus width of bank1,bank2,bank3,bank5\*/

\*((volatile unsigned int \*)S3C2410\_BWSCON) =

((\*((volatile unsigned int \*)S3C2410\_BWSCON)) & ~(0x30333<<4))

| S3C2410\_BWSCON\_DW1\_8

| S3C2410\_BWSCON\_DW2\_8

| S3C2410\_BWSCON\_DW3\_8

| S3C2410\_BWSCON\_DW5\_8;

/\* Set the interface timing between s3c2440 and st16c554 \*/

//     \*((volatile unsigned int \*)S3C2410\_BANKCON1) = 0x1f7c;

//     \*((volatile unsigned int \*)S3C2410\_BANKCON2) = 0x1f7c;

//     \*((volatile unsigned int \*)S3C2410\_BANKCON3) = 0x1f7c;

//     \*((volatile unsigned int \*)S3C2410\_BANKCON5) = 0x1f7c;

\#endif

\#ifdef CONFIG\_SPARC

ret = sunserial\_register\_minors(&serial8250\_reg, UART\_NR);

\#else

serial8250\_reg.nr = UART\_NR;

ret = uart\_register\_driver(&serial8250\_reg);

\#endif

if (ret)

goto out;

\#ifdef CONFIG\_8250\_MINI2440\_ST16C554

serial8250\_isa\_devs =

platform\_device\_alloc("serial8250", PLAT8250\_DEV\_EXAR\_ST16C554);

\#else

serial8250\_isa\_devs = platform\_device\_alloc("serial8250",

PLAT8250\_DEV\_LEGACY);

\#endif

*修改中断信号的类型为下降沿触发*

if (i->head) \{

list\_add(&up->list, i->head);

spin\_unlock\_irq(&i->lock);

ret = 0;

\} else \{

INIT\_LIST\_HEAD(&up->list);

i->head = &up->list;

spin\_unlock\_irq(&i->lock);

\#ifdef CONFIG\_SERIAL\_8250\_MINI2440\_ST16C554

irq\_flags |= IRQF\_TRIGGER\_RISING;

\#else

irq\_flags |= up->port.irqflags;

\#endif

ret = request\_irq(up->port.irq, serial8250\_interrupt,

irq\_flags, "serial", i);

if (ret < 0)

serial\_do\_unlink(i, up);

3．修改 drivers/serial/Kconfig

*添加一个编译配置选项*

config SERIAL\_8250\_MINI2440\_ST16C554

bool "Support MINI2440 Extend ST16C554/554D Quad UART"

depends on SERIAL\_8250

help

A chip of ST16C554 is uesed to extend Quad UART on the MINI2440 Board.  If you are tinkering with ST16C554, or have a machine with this UART, say Y here.

To compile this driver as a module, choose M here: the module will be called 8250\_mini2440\_st16c554.

4．重新编译内核

> make menucofig

Device Drivers   à

Character Devices  à

Serial Drivers  à

<\*> 8250/16c550 and compatible serial support

\[\*\] Support MINI2440 Extend ST16C554/554D Quad UART

保存.config文件

> make zImage

这样驱动就添加好了，如果你的根文件系统使用了mdev，那么不用做任何修改，mdev会自动地将四个新串口添加在 /dev/serial/tty目录下面，分别为 ttyS0, ttyS1, ttyS2, ttyS3。

查看更详细的信息