Android ttyS2无法打开该如何配置 + ttyS0和ttyS1可以

Step1：查找gpio datasheet《MTXXXX_GPIO_Formal_Application_Spec V1.0.xlsx》，看哪组pin可以复用为uart2.

也可以通过/vendor/mediatek/proprietary/tools/dct/MT6789.fig确认

GPIO88  =   MODE4(UTXD2) 

GPIO89  =   MODE4(URXD2)
所以需要在dws中将gpio 88，gpio 89配置成mode4
验证dws是否配置生效：
tb6789p1_64:/proc/mtk_gpio # cat soc.pinctrl

pins base: 290

PIN: (MODE)(DIR)(DOUT)(DIN)(DRIVE)(SMT)(IES)(PULL_EN)(PULL_SEL)(R1 R0)

。。。。

088: 4001000100

089: 4001000111

Step2：在平台dts文件中增加节点
1）增加uart2节点
uart2: serial@11004000 {

  compatible = "mediatek,mt6577-uart";

  reg = <0 0x11004000 0 0x1000>;

  interrupts = <GIC_SPI 143 IRQ_TYPE_LEVEL_HIGH 0>;

  clocks = <&clk26m>, <&infracfg_ao_clk CLK_IFRAO_UART2>;

  clock-names = "baud", "bus";

  dmas = <&apdma 4 &apdma 5>;

  dma-names = "tx", "rx";

  status = "okay";

  };

Step2：在平台dts文件中增加节点
2）DMA设置
apdma: dma-controller@10217800 {

  compatible = "mediatek,mt6779-uart-dma";

  reg = <0 0x10217800 0 0x80>,

  <0 0x10217880 0 0x80>,

  <0 0x10217900 0 0x80>,

  <0 0x10217980 0 0x80>,

  +  <0 0x10218000 0 0x80>,

  +  <0 0x10218080 0 0x80>;

  interrupts = <GIC_SPI 178 IRQ_TYPE_LEVEL_HIGH 0>,

  <GIC_SPI 179 IRQ_TYPE_LEVEL_HIGH 0>,

  <GIC_SPI 180 IRQ_TYPE_LEVEL_HIGH 0>,

  <GIC_SPI 181 IRQ_TYPE_LEVEL_HIGH 0>,

  +  <GIC_SPI 182 IRQ_TYPE_LEVEL_HIGH 0>,

  +  <GIC_SPI 183 IRQ_TYPE_LEVEL_HIGH 0>;

  clocks = <&infracfg_ao_clk CLK_IFRAO_AP_DMA>;

  clock-names = "apdma";

  -  dma-requests = <4>;

  +  dma-requests = <6>;

  #dma-cells = <1>;

  };

Step3：log中出现下面打印说明tty终端和uart口绑定成功，uart配置成功
[T1700001] init: [name:serial_core&]11004000.serial: ttyS2 at MMIO 0x11004000 (irq = 85, base_baud = 1625000) is a ST16650V2
Thanks!