Linux系统SPI驱动总结

平台：rk3288

系统：Android7.1 kernel4.4.143

linux spi 驱动分为三部分：

SPI外设驱动：我们写。oled，spi flash 等
linux spi核心层：drivers/spi/spi.c
芯片的SPI控制器驱动：drivers/spi/spi-rockchip.c

Linux SPI 框架理解

1、首先看dts：arch/arm/boot/dts/rk3288.dtsi

spi0: spi@ff110000 {compatible = "rockchip,rk3288-spi", "rockchip,rk3066-spi";clocks = <&cru SCLK_SPI0>, <&cru PCLK_SPI0>;clock-names = "spiclk", "apb_pclk";dmas = <&dmac_peri 11>, <&dmac_peri 12>;dma-names = "tx", "rx";interrupts = <GIC_SPI 44 IRQ_TYPE_LEVEL_HIGH>;pinctrl-names = "default";pinctrl-0 = <&spi0_clk &spi0_tx &spi0_rx &spi0_cs0>;reg = <0x0 0xff110000 0x0 0x1000>;#address-cells = <1>;#size-cells = <0>;status = "disabled";
};

2、根据这个属性匹配瑞芯微SPI控制器驱动：drivers/spi/spi-rockchip.c

static int rockchip_spi_probe(struct platform_device *pdev)
{...ret = devm_spi_register_master(&pdev->dev, master);if (ret) {dev_err(&pdev->dev, "Failed to register master\n");goto err_register_master;}return 0;...return ret;
}

3、调用 devm_spi_register_master 函数注册master 然后进入到 linux SPI的核心层，进入到 drivers/spi/spi.c 文件

drivers/spi/spi.c：
devm_spi_register_master/* 注册SPI主控制器 */ret = spi_register_master(master);/* 从设备树中注册设备 */of_register_spi_devices(master);/* 遍历可用的子项然后注册到SPI总线上 */for_each_available_child_of_node(master->dev.of_node, nc)/* 从dts里获取配置信息，reg片选属性：0、1，mode，spi-max-frequency等 */spi = of_register_spi_device(master, nc);spi_alloc_device/* 选择设备驱动程序 */of_modalias_nodecompatible = of_get_property(node, "compatible", &cplen);/*  注册新的设备 */spi_add_devicespi_setup(spi);device_add  /* 会绑定到一个spi_driver */

drivers/spi/spi.c 文件里的#if defined(CONFIG_OF) 这个判断成立的函数都是为设备树接口函数去服务的

4、SPI收发

include/linux/spi/spi.h：
spi_writespi_message_init(&m);初始化一个spi_message      /* 一个不可打断的SPI传输过程: cs=0,传数据,cs=1 *//* 一个spi_message由多个spi_transfer组成 */spi_message_add_tail(&t, &m);      /* spi_transfe是SPI上传输的单方向1个或多个字节 */spi_sync(spi, &m);      /* 启动传输并等待完成 */spi_readspi_message_init(&m);初始化一个spi_message      /* 一个不可打断的SPI传输过程: cs=0,传数据,cs=1 收数据 *//* 一个spi_message由多个spi_transfer组成 */spi_message_add_tail(&t, &m);      /* spi_transfe是SPI上传输的单方向1个或多个字节 */spi_sync(spi, &m);      /* 启动传输并等待完成 */

5、spi_driver如何调用spi_controller

drivers/spi/spi.c：
spi_sync__spi_sync(spi, message, 0);status = spi_async_locked(spi, message);ret = __spi_async(spi, message);master->transfer(spi, message);/* 等待传输完成 */wait_for_completion

不确定，因为看了控制器的传输函数名是master->transfer_one

自己写的DM412驱动，使用SPI控制器的驱动

1、驱动

/** This program is free software; you can redistribute it and/or modify* it under the terms of the GNU General Public License as published by* the Free Software Foundation; either version 2 of the License, or* (at your option) any later version.** This program is distributed in the hope that it will be useful,* but WITHOUT ANY WARRANTY; without even the implied warranty of* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the* GNU General Public License for more details.*/#include <linux/interrupt.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/workqueue.h>
#include <linux/interrupt.h>
#include <linux/delay.h>
#include <linux/clk.h>
#include <linux/fs.h>
#include <linux/dma-mapping.h>
#include <linux/dmaengine.h>
#include <linux/platform_device.h>
#include <linux/pm_runtime.h>
#include <linux/spi/spi.h>
#include <linux/gpio.h>
#include <linux/of.h>
#include <linux/of_gpio.h>
#include <linux/miscdevice.h>
#include <linux/hrtimer.h>
#include <linux/platform_data/spi-rockchip.h>
#include <asm/uaccess.h>
#include <linux/syscalls.h>static struct spi_device *g_spidev = NULL;
/*
static void dm412_read(struct spi_device *spi, void *buf, size_t len)
{int ret;ret = spi_read(spi, buf, len);if(ret)printk("spi read failed! ret = %d\n",ret);
}
*/
static void dm412_write(struct spi_device *spi, const void *buf, size_t len)
{int ret;ret = spi_write(spi, buf, len);if(ret)printk("spi write failed! ret = %d\n",ret);
}static ssize_t dm412Data_show(struct device *dev, struct device_attribute *attr, char *buf)
{return sprintf(buf, "111111\n");
}static ssize_t dm412Data_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t count)
{unsigned long dm412Data;int rc = kstrtoul(buf, 0, &dm412Data);if (rc)return rc;if (dm412Data)dm412_write(g_spidev,&dm412Data,sizeof(dm412Data));return count;
}
static DEVICE_ATTR(dm412Data, 0664, dm412Data_show, dm412Data_store);static int dm412_probe(struct spi_device *spi)
{int ret;unsigned char tx_buf[6];
//  int r = 65535;
//  int g = 0;
//  int b = 0;printk("%s\n", __func__);if (!spi)return -ENOMEM;g_spidev = spi;
/*spi->mode |= SPI_CS_HIGH;ret = spi_setup(spi);if (ret < 0) {dev_err(&spi->dev, "ERR: fail to setup spi\n");return -1;}
*/printk("%s:name=%s,bus_num=%d,cs=%d,mode=%d,speed=%d,bits_per_word=%d\n", __func__, spi->modalias, spi->master->bus_num, spi->chip_select, spi->mode, spi->max_speed_hz, spi->bits_per_word);ret = device_create_file(&spi->dev, &dev_attr_dm412Data);if (ret)printk("dm412Data device_create_file_error\n");elseprintk("dm412Data device_create_file_success\n");tx_buf[0] = 0xff;tx_buf[1] = 0xff;tx_buf[2] = 0;tx_buf[3] = 0;tx_buf[4] = 0;tx_buf[5] = 0;dm412_write(g_spidev,tx_buf,6);return ret;
}static int dm412_remove(struct spi_device *spi)
{printk("%s\n", __func__);return 0;
}static const struct of_device_id dm412_of_match[] = {{ .compatible = "siti,dm412", },{ /* Sentinel */ },
};
MODULE_DEVICE_TABLE(of, dm412_of_match);static struct spi_driver dm412_driver = {.driver = {.name = "dm412",.owner = THIS_MODULE,.of_match_table = of_match_ptr(dm412_of_match),},.probe = dm412_probe,.remove = dm412_remove,
};static int __init dm412_init(void)
{return spi_register_driver(&dm412_driver);
}
module_init(dm412_init);static void __exit dm412_exit(void)
{return spi_unregister_driver(&dm412_driver);
}
module_exit(dm412_exit);MODULE_LICENSE("GPL");
MODULE_AUTHOR("Wu Tao <wt.relax@foxmail.com>");
MODULE_DESCRIPTION("dm412 led Driver");

2、DTS配置

&spi0 {status = "okay";max-freq = <48000000>;dm412@00 {status = "okay";compatible = "siti,dm412";reg = <0>;spi-max-frequency = <20000000>;};
};

一个SPI上有两个片选引脚 CS0，CS1。这里连接的CS0。所以配置reg为0。如果不太知道dts里面怎么配置，可以查看drivers/spi/spi.c文件里of_register_spi_device函数获取了哪一些属性。还有参考瑞芯微提供的开发文档。

3、驱动最后无法使用，发现 dem412 片选脚是高电平有效。而rk3288是低电平有效。

使用GPIO口模拟可以正常使用的驱动

1、驱动

/** This program is free software; you can redistribute it and/or modify* it under the terms of the GNU General Public License as published by* the Free Software Foundation; either version 2 of the License, or* (at your option) any later version.** This program is distributed in the hope that it will be useful,* but WITHOUT ANY WARRANTY; without even the implied warranty of* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the* GNU General Public License for more details.*/#include <linux/init.h>
#include <linux/module.h>
#include <linux/delay.h>
#include <linux/clk.h>
#include <linux/fs.h>
#include <linux/dma-mapping.h>
#include <linux/dmaengine.h>
#include <linux/of_platform.h>
#include <linux/platform_device.h>
#include <linux/gpio.h>
#include <linux/of.h>
#include <linux/of_gpio.h>struct dm412_desc{struct gpio_desc *spi_sdi_gpio;struct gpio_desc *spi_scl_gpio;struct gpio_desc *spi_cs_gpio;
};struct dm412_desc *g_of_desc = NULL;static void dm412_spi0_send_cmd(struct dm412_desc *of_desc, unsigned int r, unsigned int g, unsigned int b)
{int i;gpiod_direction_output(of_desc->spi_cs_gpio, 1);for(i = 0; i < 16; i++){if(r&0x8000)gpiod_direction_output(of_desc->spi_sdi_gpio, 1);elsegpiod_direction_output(of_desc->spi_sdi_gpio, 0);gpiod_direction_output(of_desc->spi_scl_gpio, 0);udelay(20);gpiod_direction_output(of_desc->spi_scl_gpio, 1); // 时钟上升沿读取数据r <<= 1;udelay(20);}for(i = 0; i < 16; i++){if(g&0x8000)gpiod_direction_output(of_desc->spi_sdi_gpio, 1);elsegpiod_direction_output(of_desc->spi_sdi_gpio, 0);gpiod_direction_output(of_desc->spi_scl_gpio, 0);udelay(20);gpiod_direction_output(of_desc->spi_scl_gpio, 1);    // 时钟上升沿读取数据g <<= 1;udelay(20);}for(i = 0; i < 16; i++){if(b&0x8000)gpiod_direction_output(of_desc->spi_sdi_gpio, 1);elsegpiod_direction_output(of_desc->spi_sdi_gpio, 0);gpiod_direction_output(of_desc->spi_scl_gpio, 0);udelay(20);gpiod_direction_output(of_desc->spi_scl_gpio, 1);    // 时钟上升沿读取数据b <<= 1;udelay(20);}for(i = 0; i < 8; i++)   //时钟保持高电平，连发8个脉冲启动自动锁存机制{gpiod_direction_output(of_desc->spi_sdi_gpio, 0);udelay(10);gpiod_direction_output(of_desc->spi_sdi_gpio, 1);udelay(10);            }gpiod_direction_output(of_desc->spi_cs_gpio, 0);gpiod_direction_output(of_desc->spi_scl_gpio, 0);gpiod_direction_output(of_desc->spi_sdi_gpio, 0);printk("%s\n", __func__);}static ssize_t dm412Data_show(struct device *dev, struct device_attribute *attr, char *buf)
{return sprintf(buf, "please input 49bit data:(r<<32|g<<16|b).\n");
}static ssize_t dm412Data_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t count)
{unsigned long long dm412Data;unsigned int r,g,b;int rc = kstrtou64(buf, 0, &dm412Data);       // 字符串转整形if (rc)return rc;r = (dm412Data>>32)&0xffff;g = (dm412Data>>16)&0xffff;b = dm412Data&0xffff;//printk("\n spi0:\n r = %d g = %d b = %d\n ",r,g,b);dm412_spi0_send_cmd(g_of_desc, r, g, b);return count;
}
static DEVICE_ATTR(dm412Data, 0664, dm412Data_show, dm412Data_store);static int dm412_probe(struct platform_device *pdev)
{int ret;int err;struct dm412_desc *of_desc;printk("%s\n", __func__);of_desc = devm_kzalloc(&pdev->dev, sizeof(struct dm412_desc), GFP_KERNEL);if (!of_desc)return -ENOMEM;g_of_desc = of_desc;of_desc->spi_scl_gpio = devm_gpiod_get_optional(&pdev->dev, "spi-scl", 0);if (IS_ERR(of_desc->spi_scl_gpio)) {err = PTR_ERR(of_desc->spi_scl_gpio);dev_err(&pdev->dev, "failed to request spi_scl: %d\n", err);return err;}of_desc->spi_cs_gpio = devm_gpiod_get_optional(&pdev->dev, "spi-cs", 0);if (IS_ERR(of_desc->spi_cs_gpio)) {err = PTR_ERR(of_desc->spi_cs_gpio);dev_err(&pdev->dev, "failed to request spi_cs: %d\n", err);return err;}of_desc->spi_sdi_gpio = devm_gpiod_get_optional(&pdev->dev, "spi-sdi", 0);if (IS_ERR(of_desc->spi_sdi_gpio)) {err = PTR_ERR(of_desc->spi_sdi_gpio);dev_err(&pdev->dev, "failed to request spi_sdi: %d\n", err);return err;}gpiod_direction_output(of_desc->spi_cs_gpio, 0);gpiod_direction_output(of_desc->spi_sdi_gpio, 0);gpiod_direction_output(of_desc->spi_scl_gpio, 0);ret = device_create_file(&pdev->dev, &dev_attr_dm412Data);if (ret)printk("dm412Data device_create_file_error\n");elseprintk("dm412Data device_create_file_success\n");dm412_spi0_send_cmd(of_desc,168,2556,4690);return ret;
}static int dm412_remove(struct platform_device *pdev)
{printk("%s\n", __func__);return 0;
}static const struct of_device_id dm412_of_match[] = {{ .compatible = "siti,dm412", },{ /* Sentinel */ },
};
MODULE_DEVICE_TABLE(of, dm412_of_match);static struct platform_driver dm412_driver = {.driver = {.name    = "dm412",.owner = THIS_MODULE,.of_match_table = of_match_ptr(dm412_of_match),},.probe = dm412_probe,.remove = dm412_remove,
};static int __init dm412_init(void)
{return platform_driver_register(&dm412_driver);
}
module_init(dm412_init);static void __exit dm412_exit(void)
{return platform_driver_unregister(&dm412_driver);
}
module_exit(dm412_exit);MODULE_LICENSE("GPL");
MODULE_AUTHOR("Wu Tao <wt.relax@foxmail.com>");
MODULE_DESCRIPTION("dm412 led Driver");

创建的文件接口提供给APK使用

2、dts配置

dm412 {compatible = "siti,dm412";pinctrl-naems = "default";pinctrl-0 = <&spi0_init_cmd>;spi-scl-gpios = <&gpio5 12 GPIO_ACTIVE_HIGH>;spi-cs-gpios  = <&gpio5 13 GPIO_ACTIVE_HIGH>;spi-sdi-gpios = <&gpio5 14 GPIO_ACTIVE_HIGH>;status = "okay";
};