JZ2440移植Linux3.4.2之将UART2更成普通串口驱动

移植环境( 红色粗字体字为修改后内容，蓝色粗体字为特别注意内容)

1，开发板：韦东山JZ2440。

2，linux 版本：linux-3.4.2

3，参考文献：http://blog.csdn.net/fyyy4030/article/details/7243998

S3C2440 芯片具有3 个串口：UART0,1,2，我们下载的Linux-3.4.2已经具备完善的UART0,1 的驱动，但对UART2 却用作了红外通讯(Irda)，因此我们需要把UART2 驱动稍微调整一下，以便作为普通串口来用。

JZ2440串口电路如图：

于是按照参考文献操作：

【1】修改平台配置代码

我们修改内核中关于 UART2 的配置，打开linux-3.4.2/arch/arm/mach-s3c2440/mach-smdk2440.c 文件，定位到112行附近，找到mini2440_uartcfgs[]，如下红色代码为修改后的：

static struct s3c2410_uartcfg smdk2440_uartcfgs[] __initdata = {
[0] = {
.hwport = 0,
.flags = 0,
.ucon = 0x3c5,
.ulcon = 0x03,
.ufcon = 0x51,
},
[1] = {
.hwport = 1,
.flags = 0,
.ucon = 0x3c5,
.ulcon = 0x03,
.ufcon = 0x51,
},
/* IR port */
[2] = {
.hwport = 2,
.flags = 0,
.ucon = 0x3c5,
//.ulcon = 0x43,//modify by pang change the IR port to Serial port
.ulcon = 0x03,
.ufcon = 0x51,
}
};

再修改串口所使用的端口初始化，打开linux-3.4.2/drivers/tty/serial/samsung.c，定位到55行附近，先加入所需头文件，如下

#include <plat/regs-serial.h>
#include <plat/clock.h>

#include <linux/gpio.h>
#include <mach/regs-gpio.h>

#include "samsung.h"

然后再定位到456行左右，添加如下红色部分代码：

static int s3c24xx_serial_startup(struct uart_port *port)
{
struct s3c24xx_uart_port *ourport = to_ourport(port);
int ret;

dbg("s3c24xx_serial_startup: port=%p (%08lx,%p)\n",
port->mapbase, port->membase);
//---- set up Serial port 2 by pang
if(port->line == 2)
{
s3c2410_gpio_cfgpin(S3C2410_GPH(6), S3C2410_GPH6_TXD2);
s3c2410_gpio_pullup(S3C2410_GPH(6), 1);
s3c2410_gpio_cfgpin(S3C2410_GPH(7), S3C2410_GPH7_RXD2);
s3c2410_gpio_pullup(S3C2410_GPH(7), 1);
}
//---- end
rx_enabled(port) = 1;

ret = request_irq(ourport->rx_irq, s3c24xx_serial_rx_chars, 0,
s3c24xx_serial_portname(port), ourport);

if (ret != 0) {
printk(KERN_ERR "cannot get irq %d\n", ourport->rx_irq);
return ret;
}

【2】配置内核
make menuconfig

DivicesDrivers->
Characterdevices->
SerialDrivers->
<*>SansungSoC serial support

make uImage后，把arch/arm/boot/uImage加载到板子测试。

echo "fasdfasdf" >/dev/ttySAC2

------------[ cut here ]------------
WARNING: at drivers/gpio/gpio-samsung.c:3105 s3c2410_gpio_pullup+0x44/0x5c()
Modules linked in:
Backtrace:
[<c000c2a8>] (dump_backtrace+0x0/0x10c) from [<c046104c>] (dump_stack+0x18/0x1c)
r7:00000009 r6:00000c21 r5:c016ffb8 r4:00000000
[<c0461034>] (dump_stack+0x0/0x1c) from [<c00180a0>] (warn_slowpath_common+0x50/0x68)
[<c0018050>] (warn_slowpath_common+0x0/0x68) from [<c00180dc>] (warn_slowpath_null+0x24/0x2c)
r9:c31e7c00 r8:00000000 r7:00000000 r6:c0617358 r5:c0617338
r4:000000e6
[<c00180b8>] (warn_slowpath_null+0x0/0x2c) from [<c016ffb8>] (s3c2410_gpio_pullup+0x44/0x5c)
[<c016ff74>] (s3c2410_gpio_pullup+0x0/0x5c) from [<c019b340>] (s3c24xx_serial_startup+0xb0/0x110)
r5:c0617338 r4:c0617358
[<c019b290>] (s3c24xx_serial_startup+0x0/0x110) from [<c019917c>] (uart_startup+0x6c/0x1dc)
r6:c0617358 r5:c31e7c00 r4:c39f8f10
[<c0199110>] (uart_startup+0x0/0x1dc) from [<c019a138>] (uart_open+0xe8/0x130)
r9:c31e7c00 r8:c31d4000 r7:c322e2c0 r6:c39f8f40 r5:c31e7c00
r4:c39f8f10
[<c019a050>] (uart_open+0x0/0x130) from [<c0181d14>] (tty_open+0x264/0x540)
r9:c31e7c00 r8:c31d4000 r7:c38c3920 r6:0cc00042 r5:00000000
r4:c322e2c0
[<c0181ab0>] (tty_open+0x0/0x540) from [<c0088644>] (chrdev_open+0x8c/0x130)
[<c00885b8>] (chrdev_open+0x0/0x130) from [<c0083a30>] (__dentry_open+0x204/0x2c8)
r7:c3625438 r6:c380ebd0 r5:c3624958 r4:c322e2c0
[<c008382c>] (__dentry_open+0x0/0x2c8) from [<c0083bcc>] (nameidata_to_filp+0x68/0x70)
[<c0083b64>] (nameidata_to_filp+0x0/0x70) from [<c00923ec>] (do_last+0x1b8/0x6c8)
r7:00000022 r6:c3625438 r5:00000041 r4:c31d5ed0
[<c0092234>] (do_last+0x0/0x6c8) from [<c00929c0>] (path_openat+0xc4/0x38c)
[<c00928fc>] (path_openat+0x0/0x38c) from [<c0092d80>] (do_filp_open+0x38/0x8c)
[<c0092d48>] (do_filp_open+0x0/0x8c) from [<c0083650>] (do_sys_open+0xe4/0x17c)
r8:ffffff9c r7:00000001 r6:00000003 r5:00000241 r4:c3ad9000
[<c008356c>] (do_sys_open+0x0/0x17c) from [<c0083720>] (sys_open+0x24/0x28)
[<c00836fc>] (sys_open+0x0/0x28) from [<c0009220>] (ret_fast_syscall+0x0/0x2c)
---[ end trace 6acbe3f8ea2c6a74 ]---

打印一长串什么鬼东西，用示波器查看Txd引脚的波形，发现是有信号的，只是串口不发送数据的时候为低电平，发送数据的时候是高电平，这个与ttl电平相反！！！于是怀疑修改了mach-smdk2440.c但是不生效，为了验证这一想法，我把该文件故意弄成有语法错误，再次make clean ,make uImage,发现该文件也没有被编译，这就奇怪了，仔细分析编译输出，发现linux-3.4.2/arch/arm/mach-s3c24xx/mach-smdk2440.c倒是编译了，于是终于找到原因了，在linux3.4.2中编译的是mach-s3c24xx文件夹下的mach-smdk2440.c，于是在该文件中做上述改动，make uImage，dnw加载到板子上,测试，修改成功串口正常.

但是，还是有echo msg >/dev/ttyS 还是有------------[ cut here ]------------那一长串，那一长串究竟是什么意思呢？网上各种查资料都没有相应的解释，于是回到/samsung.c改动的地方，发现一个可疑的函数s3c2410_gpio_pullup，查找资料发现该函数是设置引脚高电平，会不会是这个函数的问题呢?于是注释掉这个函数，修改后如下:
//---- set up Serial port 2 by pang
if(port->line == 2)
{
s3c2410_gpio_cfgpin(S3C2410_GPH(6), S3C2410_GPH6_TXD2);
// s3c2410_gpio_pullup(S3C2410_GPH(6), 1);
s3c2410_gpio_cfgpin(S3C2410_GPH(7), S3C2410_GPH7_RXD2);
// s3c2410_gpio_pullup(S3C2410_GPH(7), 1);
}
//---- end
重新编译，正常，再也没有一长串出来了^_^。

JZ2440移植Linux3.4.2之将UART2更成普通串口驱动

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