串行驱动程序 startup/request 函数未被执行

Question

我正在为 UART（Xilinx 的 AXI UART Lite）编写我的第一个串行驱动程序。我知道内核中有一个，但我不是在嵌入式 Linux 环境中工作。

使用the documentation和现有代码作为参考，我已经实现了我的驱动程序。但是，我无法验证正在调用我的 startup 或 request_port 函数。启动函数基本上做what this does. However, not using an IRQ I'm polling. Likewise, the request_port function I have is quite similar to this function.

文档指出 the startup function 在端口打开时被调用一次。因为我在 /dev 中确实有我期望的设备节点，所以我想我需要打开端口。在 minicom 的步骤中，我打开文件（使用 lsof 验证）。然而，我可以在 dmesg 中找到 none 的消息，这些消息是我放置在我的 startup 或 request_port 函数中的。

很抱歉延迟回复，但我不得不在发布代码之前跳过一些障碍。这是我的：

#define MAX_SUPPORTED_UARTS 1
#define DRIVER_MAJOR_NUM  243  /* local/experimental */
#define DRIVER_MINOR_NUM  0

static int request_port(struct uart_port *);
static void release_port(struct uart_port *);
static int startup(struct uart_port *);
static void shutdown(struct uart_port *);

static struct uart_ops axilite_ops = {
    .release_port = release_port,
    .request_port = request_port,
    .startup = startup,
    .shutdown = shutdown,
};

static struct uart_port axilite_ports[MAX_SUPPORTED_UARTS] = {
    {
        .mapbase = 0, /* determined during discovery */
        .membase = 0, /* calcuated after learning mapbase */
        .iotype = UPIO_MEM, /* from serial_core.c */
        .irq = 0,  /* currently, device doesn't use an IRQ, just polling */
        .fifosize = 16,  /* directly Xilinx documentation */
        .ops = &axilite_ops,
        .flags = UPF_FIXED_TYPE | UPF_FIXED_PORT | UPF_SPD_VHI,
        .mctrl = TIOCM_CTS | TIOCM_DSR | TIOCM_CAR, /* from uartlite.c in kernel tree */
    },
};

static struct uart_driver axilite_driver = {
    .owner = THIS_MODULE,
    .driver_name = "axilite",
    .dev_name = "ttyAUL",
    .major = DRIVER_MAJOR_NUM,
    .minor = DRIVER_MINOR_NUM,
    .nr = MAX_SUPPORTED_UARTS,
};

static int startup(struct uart_port *pup)
{
    void __iomem* pmem = pup->membase;
    uint32_t ctlreg = 0;
    pr_info("%s:%d entry point\n", __func__, __LINE__);

    ctlreg = ioread32(CTL_REG_ADDR(pmem));
    pr_info("DEBUG: %s:%d CTL Reg is 0x%08x\n",
            __func__, __LINE__, ctlreg);
    /* clear the FIFO's */
    ctlreg |= CTL_REG_RST_TX | CTL_REG_RST_RX;
    iowrite32(ctlreg, CTL_REG_ADDR(pmem));

    return 0;
}

static void shutdown(struct uart_port *pup)
{
    void __iomem* pmem = pup->membase;

    pr_info("%s:%d entry point\n", __func__, __LINE__);

    /* Using a queue from the axilite driver in the kernel */
    iowrite32(0, CTL_REG_ADDR(pmem));
}

static void release_port(struct uart_port *pup)
{
    pr_info("%s:%d entry point\n", __func__, __LINE__);

    if (pup->membase)
        iounmap(pup->membase);

    pup->membase = NULL;
}

static int request_port(struct uart_port *pup)
{
    int result = 0;
    uint32_t bus_addr = pup->mapbase;
    void __iomem* pmem = NULL;

    pr_info("%s:%d mapping bus addr to virtual space\n",
            __func__, __LINE__);
    pmem = ioremap_nocache(bus_addr, UART_REGISTER_REGION);
    if (IS_ERR_OR_NULL(pmem)) {
        pr_err("%s:%d ioremap_nocache failed\n",
                __func__, __LINE__);
        result = PTR_ERR(pmem);
        goto startup_exit;
    }

    pup->membase = pmem;
    pr_info("%s:%d busaddr 0x%08x mapped to %p\n",
            __func__, __LINE__, bus_addr, pmem);

startup_exit:
    return result;
}

static int add_uart_ports(void)
{
    int result = 0;
    uint32_t i = 0, baseaddr = 0;

    pr_info("%s:%d adding %d port(s) to the system\n",
            __func__, __LINE__, uart_count);

    /* calls into code which learns the base address,
     * verified that it works
     */
    baseaddr = get_uart_base(i);

    if ((int)baseaddr == -EINVAL) {
        pr_err("%s:%d Invalid index used\n", __func__, __LINE__);
        result = (int)baseaddr; 
        goto add_ports_exit;
    }
    else if (0 == baseaddr) {
        pr_err("%s:%d Invalid bus address encountered, port add stopped\n",
                __func__, __LINE__);
        result = -ENODEV;
        goto add_ports_exit;
    }
    else
        axilite_port[i].mapbase = baseaddr;

    result = uart_add_one_port(&axilite_driver, &axilite_port[i]);
    if (result) {
        pr_err("%s:%d uart_add_one_port failed for port %d\n",
                __func__, __LINE__, i);
        goto add_ports_exit;
    }

    /* TODO think of a better way to track whether the port
     * is registered.  this will work for now.
     */
    axilite_port[i].private_data = &uart_count;

    init_stage |= UART_PORT_REGISTERED;

add_ports_exit:

    return result;
}

static int add_uart_driver(void)
{
    int result = 0;
    pr_info("%s:%d adding the driver\n", __func__, __LINE__);

    uart_count = get_uart_count();
    axilite_driver.nr = (int)uart_count;

    result = uart_register_driver(&axilite_driver);
    if (result) {
        pr_err("%s:%d uart_register_driver failed\n",
                __func__, __LINE__);
        goto add_driver_exit;
    }

    init_stage |= DRIVER_REGISTERED;

add_driver_exit:
    return result;
}

编辑

我没有添加平台驱动程序。虽然这是Xilinx的系统，但是我的驱动不会是嵌入式的运行Linux。鉴于此，我认为驱动程序启动类似于 the driver for 21285。这有误吗？

编辑结束

这可能是什么原因造成的？我应该做什么或检查什么？

安迪

Answer 1

你们提供平台数据吗？驱动程序本身是不够的，你必须向内核提供你的硬件存在的信息，内存映射到特定的基地址，连接到特定的中断，等等......在现代 ARM 系统上你这样做通过设备树，其他系统有不同的手段。只有在提供这些数据后，驱动程序才会加载并启动。

Answer 2

在serial_core.c uart_port_startup方法中，开头有代码：

 if (uport->type == PORT_UNKNOWN)
    return 1;

这就是没有调用启动方法的原因。您需要将 struct uart_port.type 设置为一个非未知值。至少它对我有用。您可能需要添加新的 PORT_ 类型或使用现有类型 - 不确定冲突。对于我的虚拟设备，这有效：

static struct uart_port tiny_port = {
    .ops        = &tiny_ops,
    .type       = PORT_8250,
};

串行驱动程序 startup/request 函数未被执行

serial driver startup/request functions aren't being executed

linux

driver

linux-device-driver

linux-kernel

uart