> ## Documentation Index
> Fetch the complete documentation index at: https://dragonwingdocs.qualcomm.com/llms.txt
> Use this file to discover all available pages before exploring further.

# UART

UART(通用异步收发器)使用起始位和停止位而非时钟信号来异步传输数据。接收端 UART 以称为波特率的特定频率读取数据位。

<img src="https://mintcdn.com/qualcomm-prod/jy6NQT2Y7J_sAxdX/Linux/images/peripheral-interfaces/uart_connection_diagram.png?fit=max&auto=format&n=jy6NQT2Y7J_sAxdX&q=85&s=6b6f9aae1a381ae368928049f015f74e" width="642" height="253" data-path="Linux/images/peripheral-interfaces/uart_connection_diagram.png" />

## 关键参数

* **波特率** — 通信速率(比特每秒)
* **起始/停止位** — 帧定界符
* **奇偶校验位** — 可选的错误校验
* **数据位** — 每帧 5–9 位
* **流控** — 通过 CTS/RTS 进行硬件握手

<img src="https://mintcdn.com/qualcomm-prod/jy6NQT2Y7J_sAxdX/Linux/images/peripheral-interfaces/uart_data_frame.png?fit=max&auto=format&n=jy6NQT2Y7J_sAxdX&q=85&s=88b18550eeb400ddd30f8bfc9efc6c14" width="995" height="153" data-path="Linux/images/peripheral-interfaces/uart_data_frame.png" />

## 各子系统的传输模式

| 子系统             | 传输模式         | 波特率                                  | 备注          |
| --------------- | ------------ | ------------------------------------ | ----------- |
| **Linux**       | FIFO、CPU DMA | 300 bps – 4 Mbps                     | DMA 适用于蓝牙模块 |
| **Boot (UEFI)** | 仅 FIFO       | 最高 115200                            | 每字符 5–8 位   |
| **aDSP**        | 仅 FIFO       | 115200、230400、460800、921600、1M、3M、6M | 每字符 5–8 位   |

## 接口组件

### 设备树源文件

| 平台                 | 文件                                      |
| ------------------ | --------------------------------------- |
| Dragonwing IQ-8275 | `arch/arm64/boot/dts/qcom/qcs8300.dtsi` |

### API

| 子系统   | 头文件                               |
| ----- | --------------------------------- |
| Linux | `include/linux/tty.h`             |
| Boot  | `QcomPkg/Include/HSUart.h`        |
| aDSP  | `adsp_proc/core/api/buses/uart.h` |

## 软件配置

### Linux 设备树示例

**4 线 UART(带流控):**

```dts theme={null}
uart7: serial@99c000 {
    compatible = "qcom,geni-uart";
    reg = <0 0x0099c000 0 0x4000>;
    clocks = <&gcc GCC_QUPV3_WRAP0_S7_CLK>;
    clock-names = "se";
    pinctrl-names = "default";
    pinctrl-0 = <&qup_uart7_cts>, <&qup_uart7_rts>,
                <&qup_uart7_tx>, <&qup_uart7_rx>;
    interrupts = <GIC_SPI 608 IRQ_TYPE_LEVEL_HIGH>;
    power-domains = <&rpmhpd SA8295P_CX>;
    interconnect-names = "qup-core", "qup-config";
    status = "disabled";
};
```

**QUPAC 访问控制:**

```c theme={null}
// 4-wire HS UART
{ QUPV3_0_SE7, QUPV3_PROTOCOL_UART_4W, QUPV3_MODE_FIFO, AC_HLOS, TRUE, TRUE, FALSE }

// 2-wire UART (no flow control)
{ QUPV3_0_SE5, QUPV3_PROTOCOL_UART_2W, QUPV3_MODE_FIFO, AC_HLOS, TRUE, FALSE, FALSE }
```

## 内核配置

```
CONFIG_QCOM_GENI_SE=y
CONFIG_SERIAL_QCOM_GENI=y
```

在设备树中启用 UART 节点:

```diff theme={null}
+serial1 = &uart7;

+&uart7 {
+    status = "ok";
+};
```

## 验证

<Steps>
  <Step title="验证 UART 设备注册">
    ```bash theme={null}
    ls /dev/ttyHS*
    # Expected: /dev/ttyHS1

    dmesg | grep ttyH
    ```
  </Step>

  <Step title="配置 UART 设置">
    ```bash theme={null}
    stty -F /dev/ttyHS1 115200
    ```
  </Step>

  <Step title="运行回环测试">
    打开两个 SSH 终端。

    **终端 1(写入):**

    ```bash theme={null}
    echo "Hello UART" > /dev/ttyHS1
    ```

    **终端 2(读取):**

    ```bash theme={null}
    cat /dev/ttyHS1
    ```
  </Step>
</Steps>

## 调试

```bash theme={null}
mount -t debugfs none /sys/kernel/debug
echo -n "file qcom_geni_serial.c +p" > /sys/kernel/debug/dynamic_debug/control
echo -n "file serial_core.c +p" > /sys/kernel/debug/dynamic_debug/control
dmesg | grep -i uart
dmesg | grep ttyHS
```

## 故障排除

<AccordionGroup>
  <Accordion title="未检测到 UART 设备">
    ```bash theme={null}
    lsmod | grep qcom_geni
    cat /proc/device-tree/soc@0/geniqup@*/serial*/status
    ls -la /dev/tty*
    ```

    * 确认设备树中状态为 `"ok"`
    * 确认 `CONFIG_SERIAL_QCOM_GENI=y`
  </Accordion>

  <Accordion title="数据传输失败/数据乱码">
    ```bash theme={null}
    stty -F /dev/ttyHS1 -a
    stty -F /dev/ttyHS1 115200
    stty -F /dev/ttyHS1 crtscts    # enable flow control
    stty -F /dev/ttyHS1 -crtscts   # disable flow control
    ```
  </Accordion>

  <Accordion title="权限被拒绝">
    ```bash theme={null}
    ls -la /dev/ttyHS*
    usermod -a -G dialout $USER
    ```
  </Accordion>
</AccordionGroup>

## 资源

* [Linux 内核设备树绑定](https://github.com/torvalds/linux/blob/master/Documentation/devicetree/bindings/serial/qcom%2Cserial-geni-qcom.yaml)
* [UART 驱动源码](https://github.com/torvalds/linux/blob/master/drivers/tty/serial/qcom_geni_serial.c)
* [串行控制台文档](https://docs.kernel.org/admin-guide/serial-console.html)