am335x omap serial 驱动分析

• am335x 自身的 uart 驱动集成在 kernel 的 arch/arm/mach-omap2/ 里面。

• 文件是 arch/arm/mach-omap2/serial.c

    // 看到最底部 omap_serial_init  入口函数。
    void __init omap_serial_init(void)
    {
        omap_serial_board_init(NULL);   // ---> 1.0
    }

• 1.0 omap_serial_board_init

    void __init omap_serial_board_init(struct omap_uart_port_info *info)
    {
        struct omap_uart_state *uart;     // ---> 1.1
        struct omap_board_data bdata;     // ---> 1.1
        // 这里是轮询所有 uart ，并配置基本的属性一下
        // 在这里，我们主要要弄懂 uart_list 是怎么来的，在哪里被初始化
        list_for_each_entry(uart, &uart_list, node) {
            bdata.id = uart->num;
            bdata.flags = 0;
            bdata.pads = NULL;
            bdata.pads_cnt = 0;   

            if (cpu_is_omap44xx() || (cpu_is_omap34xx() &&
                                !cpu_is_am33xx()))
                omap_serial_fill_default_pads(&bdata);  

            if (!info)
                omap_serial_init_port(&bdata, NULL);   // ---> 2.0
            else
                omap_serial_init_port(&bdata, &info[uart->num]);
        }
    }

• 1.1 struct omap_uart_state 和 struct omap_board_data

    //  arch/arm/mach-omap2/serial.c
    //
    struct omap_uart_state {
        int num;
        int can_sleep;  

        struct list_head node;
        struct omap_hwmod *oh;
        struct platform_device *pdev;
    }; 

    //  arch/arm/mach-omap2/mux.h
    //  struct omap_board_data - board specific device data
    struct omap_board_data {
        int         id;
        u32         flags;
        struct omap_device_pad  *pads;
        int         pads_cnt;
    };

• 2.0 omap_serial_init_port

    void __init omap_serial_init_port(struct omap_board_data *bdata,
            struct omap_uart_port_info *info)
    {
        struct omap_uart_state *uart;
        struct omap_hwmod *oh;
        struct platform_device *pdev;
        void *pdata = NULL;
        u32 pdata_size = 0;
        char *name;
        struct omap_uart_port_info omap_up;                                         

        if (WARN_ON(!bdata))
            return;
        if (WARN_ON(bdata->id < 0))
            return;
        if (WARN_ON(bdata->id >= num_uarts))
            return;                                                                 

        list_for_each_entry(uart, &uart_list, node)
            if (bdata->id == uart->num)
                break;
        if (!info)
            info = omap_serial_default_info;                                        

        oh = uart->oh;
        name = DRIVER_NAME;                                                         

        omap_up.dma_enabled = info->dma_enabled;
        omap_up.uartclk = OMAP24XX_BASE_BAUD * 16;
        omap_up.flags = UPF_BOOT_AUTOCONF;
        omap_up.get_context_loss_count = omap_pm_get_dev_context_loss_count;
        omap_up.set_forceidle = omap_uart_set_forceidle;
        omap_up.set_noidle = omap_uart_set_noidle;
        omap_up.enable_wakeup = omap_uart_enable_wakeup;
        omap_up.dma_rx_buf_size = info->dma_rx_buf_size;
        omap_up.dma_rx_timeout = info->dma_rx_timeout;
        omap_up.dma_rx_poll_rate = info->dma_rx_poll_rate;
        omap_up.autosuspend_timeout = info->autosuspend_timeout;                    

        /* Enable the MDR1 Errata i202 for OMAP2430/3xxx/44xx */
        if (!cpu_is_omap2420() && !cpu_is_ti816x())
            omap_up.errata |= UART_ERRATA_i202_MDR1_ACCESS;                         

        /* Enable DMA Mode Force Idle Errata i291 for omap34xx/3630 */
        if ((cpu_is_omap34xx() || cpu_is_omap3630()) && !cpu_is_am33xx())
            omap_up.errata |= UART_ERRATA_i291_DMA_FORCEIDLE;                       

        pdata = &omap_up;
        pdata_size = sizeof(struct omap_uart_port_info);                            

        if (WARN_ON(!oh))
            return;                                                                 

        pdev = omap_device_build(name, uart->num, oh, pdata, pdata_size,
                     NULL, 0, false);
        WARN(IS_ERR(pdev), "Could not build omap_device for %s: %s.\n",
             name, oh->name);                                                       

        if ((console_uart_id == bdata->id) && no_console_suspend)
            omap_device_disable_idle_on_suspend(pdev);                              

        oh->mux = omap_hwmod_mux_init(bdata->pads, bdata->pads_cnt);                

        uart->pdev = pdev;                                                          

        oh->dev_attr = uart;                                                        

        if (((cpu_is_omap34xx() || cpu_is_omap44xx()) && bdata->pads)
                && !uart_debug)
            device_init_wakeup(&pdev->dev, true);
    }