SPI总线（三）：驱动实例
相关文章：
SPI总线（一）：基本原理篇
SPI总线（二）：驱动分析篇
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
#include
#include
#include
#include
#include
#include
#include
#include
#include
#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。