【平台信息】

Android：9.0
CPU：S905D3
SPI转串口：CH432T

【硬件连接】

编号 S905D3 CH432T
1 GPIOA_1 INT#

说明：
1、CH432T如果只连接 INT#引脚，即两个串口合用一个中断请求，那么单片机在进入中断服务程序后，首
先应该分析出是哪个串口的中断请求。
2、CH432T当 INT0 或者 INT1其中一个有效时（三态输出允许且输出高电平），INT#引脚输出低电平，否则 INT#引脚不输出。
3、CH432 芯片的 SPI 片选 , 低电平有效

【基本概念】

spi_master：确定芯片spi控制器。
spi_device：确定总线的一些属性，比如spi的mode，cs片选，频率等。
spi_driver：描述总线下挂载的设备的驱动，比如spi norflash的驱动和spi lcd的驱动等。

【代码梳理】

1、SPI Master驱动

           spicc0: spi@13000 {compatible = "amlogic,meson-g12a-spicc";reg = <0x0 0x13000 0x0 0x44>;interrupts = <GIC_SPI 81 IRQ_TYPE_LEVEL_HIGH>;clocks = <&clkc CLKID_SPICC0>,<&clkc CLKID_SPICC0_COMP>;clock-names = "core", "comp";#address-cells = <1>;#size-cells = <0>;status = "disabled";};}

驱动代码：common/drivers/spi/spi-meson-spicc.c

meson_spicc_probe->devm_spi_register_master->spi_register_master-> //注册一个spi控制器，即spi_masterof_spi_register_master->of_register_spi_devices->    // 解析设备树，创建SPI deviceof_register_spi_device-> // 设备树匹配操作spi_add_device->
static void of_register_spi_devices(struct spi_master *master)
{...for_each_available_child_of_node(master->dev.of_node, nc) {...spi = of_register_spi_device(master, nc);...}
}    
drivers\spi\spi.c
spi_drv_probe->spi->irq = of_irq_get(dev->of_node, 0);    //获取irq中断号  

1、SPI Device驱动

1）ch432 DTS设备配置

&spicc0 {status = "okay";spidev0 {#address-cells = <1>;#size-cells = <1>;compatible = "wch,ch43x";reg = <0>;spi-max-frequency = <5000000>;interrupt_pin = <&gpio GPIOA_1 GPIO_ACTIVE_LOW>;irq_trigger_type = "GPIO_IRQ_LOW";status = "okay";};
};

2）驱动注册

static const struct of_device_id __maybe_unused ch43x_dt_ids[] = {{ .compatible = "wch,ch43x",	.data = &ch43x_devtype, },{},
};
static struct spi_driver ch43x_spi_uart_driver = {.driver = {.name   = CH43X_NAME_SPI,.bus    = &spi_bus_type,.owner  = THIS_MODULE,.of_match_table = of_match_ptr(ch43x_dt_ids),},.probe          = ch43x_spi_probe,.remove         = ch43x_spi_remove,
};
static int __init ch43x_init(void)
{return spi_register_driver(&ch43x_spi_uart_driver);
}
module_init(ch43x_init);

查看上面的代码，ch43x_spi_uart_driver注册到module_spi_driver，表示在系统启动的时候会把这个结构体添加到spi driver的链表中，当有新的driver这时候会去查找是否有和它匹配的device，如果查找到匹配的device，ch43x_spi_uart_driver里面的probe函数就会被调用!

【调试记录】

1、编译tty_test测试工具
/opt/gcc-linaro-6.3.1-2017.02-x86_64_aarch64-linux-gnu/bin/aarch64-linux-gnu-gcc -o tty_test --static tty_test.c
说明：如何确定交叉编译工具路径？
—》在kernel工程中搜索Makefile文件中的CROSS_COMPILE变量，
然后在Makefile设置CROSS_COMPILE变量后加打印$(warning $(CROSS_COMPILE))，看编译日志；

2、查看SPI设备

:/data # cat /sys/bus/spi/devices/spi32766.0/modalias
spi:ch43x
:/data # ls -l /dev/ttyWCH*
crw------- 1 root root 243,   0 1970-01-01 08:00 /dev/ttyWCH0
crw------- 1 root root 243,   1 1970-01-01 08:00 /dev/ttyWCH1

3、设置串口参数

busybox stty -F /dev/ttyWCH0 speed 115200 raw cs8 -parenb –cstopb
busybox stty -a -F /dev/ttyWCH0busybox stty -F /dev/ttyWCH1 speed 115200 raw cs8 -parenb –cstopb 
busybox stty -a -F /dev/ttyWCH1

【参考链接】

1、linux3.10系统下CH432T(SPI转串口)调试笔记
https://blog.csdn.net/u010936265/article/details/114181275?ops_request_misc=%257B%2522request%255Fid%2522%253A%2522163575419316780265454182%2522%252C%2522scm%2522%253A%252220140713.130102334…%2522%257D&request_id=163575419316780265454182&biz_id=0&utm_medium=distribute.pc_search_result.none-task-blog-2_allsobaiduend~default-2-114181275.pc_search_result_hbase_insert&utm_term=ch432t&spm=1018.2226.3001.4187

2、嵌入式linux spi转CH432驱动
https://blog.csdn.net/yin_feiling/article/details/7545321?ops_request_misc=%257B%2522request%255Fid%2522%253A%2522163575419316780265454182%2522%252C%2522scm%2522%253A%252220140713.130102334…%2522%257D&request_id=163575419316780265454182&biz_id=0&utm_medium=distribute.pc_search_result.none-task-blog-2_allsobaiduend~default-5-7545321.pc_search_result_hbase_insert&utm_term=ch432t&spm=1018.2226.3001.4187

3、Linux SPI 驱动分析（1）— 结构框架
https://blog.csdn.net/zhoutaopower/article/details/99866773?ops_request_misc=%257B%2522request%255Fid%2522%253A%2522163581605016780261912882%2522%252C%2522scm%2522%253A%252220140713.130102334…%2522%257D&request_id=163581605016780261912882&biz_id=0&utm_medium=distribute.pc_search_result.none-task-blog-2_allbaidu_landing_v2~default-2-99866773.pc_search_result_hbase_insert&utm_term=linux+spi%E9%A9%B1%E5%8A%A8&spm=1018.2226.3001.4187

4、OpenWrt 之 MT7628 移植第三方SPI驱动
https://blog.csdn.net/JAZZSOLDIER/article/details/105117141