前言
之前对SPI驱动的整体架构做了介绍，现在来分析具体的驱动程序。之前说过，SPI驱动分为设备驱动和控制器驱动。先来分析控制器驱动。我们以RockChip的控制器来作为分析。
SPI控制器分析
下面的代码分析主要都在注释中，会按照驱动中函数的执行顺序分析。
(1) 装载和卸载函数
//dts匹配表staticconststructof_device_idrockchip_spi_dt_match[] = { { .compatible="rockchip,rv1108-spi", }, { .compatible="rockchip,rk3036-spi", }, { .compatible="rockchip,rk3066-spi", }, { .compatible="rockchip,rk3188-spi", }, { .compatible="rockchip,rk3228-spi", }, { .compatible="rockchip,rk3288-spi", }, { .compatible="rockchip,rk3368-spi", }, { .compatible="rockchip,rk3399-spi", }, { }, }; MODULE_DEVICE_TABLE(of, rockchip_spi_dt_match); staticstructplatform_driverrockchip_spi_driver= { .driver= { .name=DRIVER_NAME, .pm=&rockchip_spi_pm, .of_match_table=of_match_ptr(rockchip_spi_dt_match), }, .probe=rockchip_spi_probe, .remove=rockchip_spi_remove, }; //宏封装了platform_driver_register和platform_driver_unregistermodule_platform_driver(rockchip_spi_driver);
module_platform_driver宏定义在 include/linux/platform_device.h， 具体看一下源码：
#define module_platform_driver(__platform_driver) \ module_driver(__platform_driver, platform_driver_register, \ platform_driver_unregister) #define module_driver(__driver, __register, __unregister, ...) \ static int __init __driver##_init(void) \ { \ return __register(&(__driver) , ##__VA_ARGS__); \ } \ module_init(__driver##_init); \ static void __exit __driver##_exit(void) \ { \ __unregister(&(__driver) , ##__VA_ARGS__); \ } \ module_exit(__driver##_exit);
所以其实和我们看到的platform_driver的注册和卸载时一样的，只是进行了封装。
(2) probe()函数
staticintrockchip_spi_probe(structplatform_device*pdev) { intret; structrockchip_spi*rs; structspi_master*master; structresource*mem; u32rsd_nsecs; //分配一个spi_mastermaster=spi_alloc_master(&pdev->dev, sizeof(structrockchip_spi)); //保存为driver_data， 方便其他地方获取使用platform_set_drvdata(pdev, master); //获取设备数据，就是driver_datars=spi_master_get_devdata(master); //获取IO资源mem=platform_get_resource(pdev, IORESOURCE_MEM, 0); //申请IO资源并进行重映射rs->regs=devm_ioremap_resource(&pdev->dev, mem); //获取APB时钟(APB时钟)rs->apb_pclk=devm_clk_get(&pdev->dev, "apb_pclk"); //获取spi时钟(APB提供)rs->spiclk=devm_clk_get(&pdev->dev, "spiclk"); //使能APB时钟ret=clk_prepare_enable(rs->apb_pclk); //使能spi时钟ret=clk_prepare_enable(rs->spiclk); //关闭spi控制器(设置SSIENR寄存器的值)，查看芯片手册spi_enable_chip(rs, 0); rs->type=SSI_MOTO_SPI; //摩托罗拉SPI协议rs->master=master; //spi_masterrs->dev=&pdev->dev; //devicers->max_freq=clk_get_rate(rs->spiclk); //最大时钟频率//接收采样延迟时间if (!of_property_read_u32(pdev->dev.of_node, "rx-sample-delay-ns", &rsd_nsecs)) rs->rsd_nsecs=rsd_nsecs; //FIFO大小rs->fifo_len=get_fifo_len(rs); spin_lock_init(&rs->lock); //电源管理pm_runtime_set_active(&pdev->dev); pm_runtime_enable(&pdev->dev); master->auto_runtime_pm=true; //自动电源管理master->bus_num=pdev->id; //哪个spi， 比如是SPI1就bus_num=1, SPI2就bus_num=2master->mode_bits=SPI_CPOL|SPI_CPHA|SPI_LOOP; //所支持的模式master->num_chipselect=ROCKCHIP_SPI_MAX_CS_NUM; //片选最大值+1,spi设备的片选值要小于它master->dev.of_node=pdev->dev.of_node; master->bits_per_word_mask=SPI_BPW_MASK(16) |SPI_BPW_MASK(8);//支持8或16bit//回调函数master->set_cs=rockchip_spi_set_cs; //硬件片选，使用控制器的片选(没使用可以不实现)master->prepare_message=rockchip_spi_prepare_message;//设置spi控制器(传输前的准备)master->unprepare_message=rockchip_spi_unprepare_message; //释放prepare的资源master->transfer_one=rockchip_spi_transfer_one;//传输一个简单的spi_transfermaster->max_transfer_size=rockchip_spi_max_transfer_size; master->handle_err=rockchip_spi_handle_err; master->flags=SPI_MASTER_GPIO_SS; //使用DMArs->dma_tx.ch=dma_request_chan(rs->dev, "tx"); rs->dma_rx.ch=dma_request_chan(rs->dev, "rx"); if (rs->dma_tx.ch&&rs->dma_rx.ch) { //FIFO的地址rs->dma_tx.addr= (dma_addr_t)(mem->start+ROCKCHIP_SPI_TXDR); rs->dma_rx.addr= (dma_addr_t)(mem->start+ROCKCHIP_SPI_RXDR); master->can_dma=rockchip_spi_can_dma; master->dma_tx=rs->dma_tx.ch; master->dma_rx=rs->dma_rx.ch; } //注册spi_masterret=devm_spi_register_master(&pdev->dev, master); return0; //错误处理//.....returnret; }
上面将一些错误判断及Log信息去掉了，只留下关键的部分。
(3) 传输函数 -- rockchip_spi_transfer_one
staticintrockchip_spi_transfer_one( structspi_master*master, structspi_device*spi, structspi_transfer*xfer) { //获取rockchip_spistructrockchip_spi*rs=spi_master_get_devdata(master); //判断spi当前状态WARN_ON(readl_relaxed(rs->regs+ROCKCHIP_SPI_SSIENR) && (readl_relaxed(rs->regs+ROCKCHIP_SPI_SR) &SR_BUSY)); if (!xfer->tx_buf&&!xfer->rx_buf) { dev_err(rs->dev, "No buffer for transfer\n"); return-EINVAL; } if (xfer->len>ROCKCHIP_SPI_MAX_TRANLEN) { dev_err(rs->dev, "Transfer is too long (%d)\n", xfer->len); return-EINVAL; } rs->speed=xfer->speed_hz; //传输速率rs->bpw=xfer->bits_per_word; //8bit或16bitrs->n_bytes=rs->bpw>>3; //传输的数据rs->tx=xfer->tx_buf; rs->tx_end=rs->tx+xfer->len; rs->rx=xfer->rx_buf; rs->rx_end=rs->rx+xfer->len; rs->len=xfer->len; rs->tx_sg=xfer->tx_sg; rs->rx_sg=xfer->rx_sg; if (rs->tx&&rs->rx) rs->tmode=CR0_XFM_TR; //发送并接收elseif (rs->tx) rs->tmode=CR0_XFM_TO; //只发送elseif (rs->rx) rs->tmode=CR0_XFM_RO; //只接收/* we need prepare dma before spi was enabled *///是否使用DMAif (master->can_dma&&master->can_dma(master, spi, xfer)) rs->use_dma=true; elsers->use_dma=false; //配置spi，对寄存器进行配置rockchip_spi_config(rs); if (rs->use_dma) returnrockchip_spi_prepare_dma(rs); //数据传输returnrockchip_spi_pio_transfer(rs); }
- rockchip_spi_pio_transfer
staticintrockchip_spi_pio_transfer(structrockchip_spi*rs) { intremain=0; //使能SPIspi_enable_chip(rs, 1); do { if (rs->tx) { remain=rs->tx_end-rs->tx; rockchip_spi_pio_writer(rs); //发送 } if (rs->rx) { remain=rs->rx_end-rs->rx; rockchip_spi_pio_reader(rs); //读取 } cpu_relax(); } while (remain); /* If tx, wait until the FIFO data completely. */if (rs->tx) wait_for_idle(rs); //关闭SPIspi_enable_chip(rs, 0); return0; }
- rockchip_spi_pio_writer
//发送staticvoidrockchip_spi_pio_writer(structrockchip_spi*rs) { u32max=tx_max(rs); u32txw=0; while (max--) { if (rs->n_bytes==1) txw=*(u8*)(rs->tx); elsetxw=*(u16*)(rs->tx); //写到数据发送寄存器writel_relaxed(txw, rs->regs+ROCKCHIP_SPI_TXDR); rs->tx+=rs->n_bytes; } } //读取staticvoidrockchip_spi_pio_reader(structrockchip_spi*rs) { u32max=rx_max(rs); u32rxw; while (max--) { //读取数据接收寄存器中的数据rxw=readl_relaxed(rs->regs+ROCKCHIP_SPI_RXDR); if (rs->n_bytes==1) *(u8*)(rs->rx) = (u8)rxw; else*(u16*)(rs->rx) = (u16)rxw; rs->rx+=rs->n_bytes; } }
总结
每次看到这么多代码分析，很多人肯定都不怎么想看，但是多看几份，你就会发现都是套路。每个Linux版本的结构体可能都会变，但是基本的东西都是不变的。大家可以和之前的SPI驱动架构分析那篇文章一起看。
