SPI总线（三）：驱动实例

本文转自https://blog.youkuaiyun.com/kai_zone/article/details/78043303

平台：firefly-rk3399

详细配置参照：http://www.t-firefly.com/doc/product/info/id/92.html#SPI.E5.B7.A5.E4.BD.9C.E6.96.B9.E5.BC.8F

   

     

      

     
     

      

       /*
      
     

     

      

     
     

      

        * Driver for pwm demo on Firefly board.
      
     

     

      

     
     

      

        *
      
     

     

      

     
     

      

        * Copyright (C) 2016, Zhongshan T-chip Intelligent Technology Co.,ltd.
      
     

     

      

     
     

      

        * Copyright 2006  Sam Chan
      
     

     

      

     
     

      

        *
      
     

     

      

     
     

      

        * This program is free software; you can redistribute it and/or modify
      
     

     

      

     
     

      

        * it under the terms of the GNU General Public License version 2 as
      
     

     

      

     
     

      

        * published by the Free Software Foundation.
      
     

     

      

     
     

      

        */
      
     

     

      

     
     

      

       #define DEBUG
      
     

     

      

     
     

      

       #include <linux/module.h>
      
     

     

      

     
     

      

       #include <linux/kernel.h>
      
     

     

      

     
     

      

       #include <linux/init.h>
      
     

     

      

     
     

      

       #include <linux/err.h>
      
     

     

      

     
     

      

       #include <linux/io.h>
      
     

     

      

     
     

      

       #include <linux/of.h>
      
     

     

      

     
     

      

       #include <linux/interrupt.h>
      
     

     

      

     
     

      

       #include <linux/platform_device.h>
      
     

     

      

     
     

      

       #include <linux/spi/spi.h>
      
     

     

      

     
     

      

       #include <linux/spi/spidev.h>
      
     

     

      

     
     

      
 
      
     

     

      

     
     

      

       #define FIREFLY_SPI_READ_ID_CMD 0x9F
      
     

     

      

     
     

      
 
      
     

     

      

     
     

      

       #define FIREFLY_SPI_PRINT_ID(rbuf) \
      
     

     

      

     
     

      

          do { \
      
     

     

      

     
     

      

              
       if
        (status == 0) \
      
     

     

      

     
     

      

                   dev_dbg(&spi->dev, 
       ”%s: ID = %02x %02x %02x %02x %02x\n”
       , __FUNCTION__, \
      
     

     

      

     
     

      

                       rbuf[0], rbuf[1], rbuf[2], rbuf[3], rbuf[4]); \
      
     

     

      

     
     

      

             
       else
        \
      
     

     

      

     
     

      

                   dev_err(&spi->dev, 
       ”%s: read ID error\n”
       , __FUNCTION__); \
      
     

     

      

     
     

      

          }while(0)
      
     

     

      

     
     

      
 
      
     

     

      

     
     

      

       static int firefly_spi_read_w25x_id_0(struct spi_device *spi)
      
     

     

      

     
     

      

       {   
      
     

     

      

     
     

      
    
       int status;
      
     

     

      

     
     

      
 
       char tbuf[]={FIREFLY_SPI_READ_ID_CMD};
      
     

     

      

     
     

      
  
       char rbuf[
       5];
      
     

     

      

     
     

      
 
      
     

     

      

     
     

      
    
       struct spi_transfer t = {
      
     

     

      

     
     

      

            .tx_buf     = tbuf,
      
     

     

      

     
     

      

            .len        = 
       sizeof(tbuf),
      
     

     

      

     
     

      

        };
      
     

     

      

     
     

      
 
      
     

     

      

     
     

      
 
       struct spi_transfer r = {
      
     

     

      

     
     

      

              .rx_buf         = rbuf,
      
     

     

      

     
     

      

            .len            = 
       sizeof(rbuf),
      
     

     

      

     
     

      

        };
      
     

     

      

     
     

      
  
       struct spi_message m;
      
     

     

      

     
     

      
 
      
     

     

      

     
     

      

        spi_message_init(&m);
      
     

     

      

     
     

      

          spi_message_add_tail(&t, &m);
      
     

     

      

     
     

      

          spi_message_add_tail(&r, &m);
      
     

     

      

     
     

      

          status = spi_sync(spi, &m);
      
     

     

      

     
     

      
 
      
     

     

      

     
     

      

           FIREFLY_SPI_PRINT_ID(rbuf);
      
     

     

      

     
     

      
 
       return status;
      
     

     

      

     
     

      

       }
      
     

     

      

     
     

      
 
      
     

     

      

     
     

      
 
      
     

     

      

     
     

      

       static int firefly_spi_read_w25x_id_1(struct spi_device *spi)
      
     

     

      

     
     

      

       {
      
     

     

      

     
     

      
   
       int status;
      
     

     

      

     
     

      
 
       char tbuf[] = {FIREFLY_SPI_READ_ID_CMD};
      
     

     

      

     
     

      
    
       char rbuf[
       5];
      
     

     

      

     
     

      
 
      
     

     

      

     
     

      

           status = spi_write_then_read(spi, tbuf, 
       sizeof(tbuf), rbuf, 
       sizeof(rbuf));
      
     

     

      

     
     

      
  
      
     

     

      

     
     

      

           FIREFLY_SPI_PRINT_ID(rbuf);
      
     

     

      

     
     

      
 
       return status;
      
     

     

      

     
     

      

       }
      
     

     

      

     
     

      
 
      
     

     

      

     
     

      

       static int firefly_spi_probe(struct spi_device *spi)
      
     

     

      

     
     

      

       {
      
     

     

      

     
     

      
    
       int ret = 
       0;
      
     

     

      

     
     

      
    
       struct device_node __maybe_unused *np = spi->dev.of_node;
      
     

     

      

     
     

      
 
      
     

     

      

     
     

      

           dev_dbg(&spi->dev, 
       ”Firefly SPI demo program\n”);
      
     

     

      

     
     

      
 
      
     

     

      

     
     

      
   
       if(!spi)    
      
     

     

      

     
     

      
        
       return -ENOMEM;
      
     

     

      

     
     

      
 
      
     

     

      

     
     

      

           dev_dbg(&spi->dev, 
       ”firefly_spi_probe: setup mode %d, %s%s%s%s%u bits/w, %u Hz max\n”,
      
     

     

      

     
     

      

                (
       int) (spi->mode & (SPI_CPOL | SPI_CPHA)),
      
     

     

      

     
     

      

                  (spi->mode & SPI_CS_HIGH) ? 
       ”cs_high, “ : 
       ”“,
      
     

     

      

     
     

      

                   (spi->mode & SPI_LSB_FIRST) ? 
       ”lsb, “ : 
       ”“,
      
     

     

      

     
     

      

                 (spi->mode & SPI_3WIRE) ? 
       ”3wire, “ : 
       ”“,
      
     

     

      

     
     

      

                   (spi->mode & SPI_LOOP) ? 
       ”loopback, “ : 
       ”“,
      
     

     

      

     
     

      

                 spi->bits_per_word, spi->max_speed_hz);
      
     

     

      

     
     

      
 
      
     

     

      

     
     

      

         firefly_spi_read_w25x_id_0(spi);
      
     

     

      

     
     

      

           firefly_spi_read_w25x_id_1(spi);
      
     

     

      

     
     

      
    
      
     

     

      

     
     

      
    
       return ret;
      
     

     

      

     
     

      

       }
      
     

     

      

     
     

      
 
      
     

     

      

     
     

      

       static 
       struct of_device_id firefly_match_table[] = {
      
     

     

      

     
     

      

          { .compatible = 
       ”firefly,rk3399-spi”,},
      
     

     

      

     
     

      

          {},
      
     

     

      

     
     

      

       };
      
     

     

      

     
     

      
 
      
     

     

      

     
     

      

       static 
       struct spi_driver firefly_spi_driver = {
      
     

     

      

     
     

      

          .driver = {
      
     

     

      

     
     

      

               .name = 
       ”firefly-spi”,
      
     

     

      

     
     

      

              .owner = THIS_MODULE,
      
     

     

      

     
     

      

             .of_match_table = firefly_match_table,
      
     

     

      

     
     

      

        },
      
     

     

      

     
     

      

        .probe = firefly_spi_probe,
      
     

     

      

     
     

      

       };
      
     

     

      

     
     

      
 
      
     

     

      

     
     

      

       static int firefly_spi_init(void)
      
     

     

      

     
     

      

       {
      
     

     

      

     
     

      
 
       return spi_register_driver(&firefly_spi_driver);
      
     

     

      

     
     

      

       }
      
     

     

      

     
     

      

       module_init(firefly_spi_init);
      
     

     

      

     
     

      
 
      
     

     

      

     
     

      

       static void firefly_spi_exit(void)
      
     

     

      

     
     

      

       {
      
     

     

      

     
     

      

        spi_unregister_driver(&firefly_spi_driver);
      
     

     

      

     
     

      

       }
      
     

     

      

     
     

      

       module_exit(firefly_spi_exit);
      
     

     

      

     
     

      
 
      
     

     

      

     
     

      
 
      
     

     

      

     
     

      

       MODULE_DESCRIPTION(
       ”Firefly SPI demo driver”);
      
     

     

      

     
     

      

       MODULE_ALIAS(
       ”platform:firefly-spi”);
      
     

     

      

     
     

      

       MODULE_LICENSE(
       ”GPL”);
      
     
   

此驱动只是实现简单的读取设备的ID，然后打印出来，并没有实现API接口

firefly_spi_probe中使用了两种接口操作读取W25Q128FV的ID:
firefly_spi_read_w25x_id_0接口直接使用了spi_transfer和spi_message来传送数据。
firefly_spi_read_w25x_id_1接口则使用SPI接口spi_write_then_read来读写数据。

编写spi驱动时，读写设备科参照此驱动，添加spi的API接口。