原始代码只有串口1-3。添加串口4按照以下几个步骤：
1.修改arch/arm/mach-omap2/serial.c
添加串口4的信息101 static struct plat_serial8250_port serial_platform_data2[] = {
102 {
103 .mapbase = OMAP_UART3_BASE,
104 .irq = 74,
105 .flags = UPF_BOOT_AUTOCONF,
106 .iotype = UPIO_MEM,
107 .regshift = 2,
108 .uartclk = OMAP24XX_BASE_BAUD * 16,
109 }, {
110 .flags = 0
111 }
112 };
113
114 //#ifdef CONFIG_ARCH_OMAP4
115 static struct plat_serial8250_port serial_platform_data3[] = {
116 {
117 .mapbase = OMAP_UART4_BASE,
118 #ifdef CONFIG_ARCH_OMAP3
119 .irq = 80,
120 #elif defined (CONFIG_ARCH_OMAP4)
121 .irq = 70,
122 #endif
123 .flags = UPF_BOOT_AUTOCONF,
124 .iotype = UPIO_MEM,
125 .regshift = 2,
126 .uartclk = OMAP24XX_BASE_BAUD * 16,
127 }, {
128 .flags = 0
129 }
130 };
131 //#endif
添加串口4的寄存器宏定义
383 /* CM_FCLKEN_PER, CM_ICLKEN_PER, PM_WKEN_PER shared bits */
384 #define OMAP3630_EN_UART4 (1 << 18)
385 #define OMAP3630_EN_UART4_SHIFT (18)
425 /* CM_IDLEST_PER, PM_WKST_PER shared bits */
426 #define OMAP3630_ST_UART4_MASK (1 << 18)
427 #define OMAP3630_ST_UART4_SHIFT 18
这个文件应该是配置时钟，外设使能的
按照uart3的配置添加uart4的
2563 static struct clk uart3_fck = {
2564 .name = "uart3_fck",
2565 .ops = &clkops_omap2_dflt_wait,
2566 .parent = &per_48m_fck,
2567 .enable_reg = OMAP_CM_REGADDR(OMAP3430_PER_MOD, CM_FCLKEN),
2568 .enable_bit = OMAP3430_EN_UART3_SHIFT,
2569 .clkdm_name = "per_clkdm",
2570 .recalc = &followparent_recalc,
2571 };
2572
2573 static struct clk uart4_fck = {
2574 .name = "uart4_fck",
2575 .ops = &clkops_omap2_dflt_wait,
2576 .parent = &per_48m_fck,
2577 .enable_reg = OMAP_CM_REGADDR(OMAP3430_PER_MOD, CM_FCLKEN),
2578 .enable_bit = OMAP3630_EN_UART4_SHIFT,
2579 .clkdm_name = "per_clkdm",
2580 .recalc = &followparent_recalc,
2581 };
2823 static struct clk uart3_ick = {
2824 .name = "uart3_ick",
2825 .ops = &clkops_omap2_dflt_wait,
2826 .parent = &per_l4_ick,
2827 .enable_reg = OMAP_CM_REGADDR(OMAP3430_PER_MOD, CM_ICLKEN),
2828 .enable_bit = OMAP3430_EN_UART3_SHIFT,
2829 .clkdm_name = "per_clkdm",
2830 .recalc = &followparent_recalc,
2831 };
2832 static struct clk uart4_ick = {
2833 .name = "uart4_ick",
2834 .ops = &clkops_omap2_dflt_wait,
2835 .parent = &per_l4_ick,
2836 .enable_reg = OMAP_CM_REGADDR(OMAP3430_PER_MOD, CM_ICLKEN),
2837 .enable_bit = OMAP3630_EN_UART4_SHIFT,
2838 .clkdm_name = "per_clkdm",
2839 .recalc = &followparent_recalc,
2840 };
3451 CLK(NULL, "per_48m_fck", &per_48m_fck, CK_3XXX),
3452 CLK(NULL, "uart3_fck", &uart3_fck, CK_3XXX),
3453 CLK(NULL, "uart4_fck", &uart4_fck, CK_3XXX),
3454 CLK(NULL, "gpt2_fck", &gpt2_fck, CK_3XXX),
3475 CLK(NULL, "wdt3_ick", &wdt3_ick, CK_3XXX),
3476 CLK(NULL, "uart3_ick", &uart3_ick, CK_3XXX),
3477 CLK(NULL, "uart4_ick", &uart4_ick, CK_3XXX),
3478 CLK(NULL, "gpt9_ick", &gpt9_ick, CK_3XXX),