[Mod] 更新文档
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gaoyang3513
141
spi/ReadMe.md
141
spi/ReadMe.md
@ -2,6 +2,7 @@
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## 参考
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- linux_5.10/Documentation/spi/spi-summary.rst
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@ -15,10 +16,12 @@
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### 两种SPI驱动
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#### Controller drivers ...
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此类驱动的对象为SOC片上的SPI控制器，这些控制器通常支持“Master”与“Slave”角色切换。
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此类驱动常直接访问硬件寄存器并使用DMA来提高数据传递效率，或许也可以通过CPU控制数据的每一位来控制可编程GPIO管脚。
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#### Protocol drivers ...
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此类驱动的对象为SOC片外接的SPI设备，这些设备以“Master”或“Slave”角色接入SPI控制器,进而完成数据的传输。
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在SPI驱动之上，可能被具象化为MTD、Audio等设备接入更上一级的子系统。
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@ -56,13 +59,16 @@ SPI设备必须管理以下两种类型内存：
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## 示例
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### 静态定义
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### 设备
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#### 板级设备
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#### 板级静态定义
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##### Master
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"struct platform_device"
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- `struct platform_device`, 基于平台设备开发;
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路径：`arch/.../mach-*/board-*.c`:
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```c
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#include <mach/spi.h> /* for mysoc_spi_data */
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@ -105,8 +111,11 @@ SPI设备必须管理以下两种类型内存：
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...
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}
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```
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##### Slave
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文件：`arch/.../mach-*/board-*.c`：
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```c
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static struct ads7846_platform_data ads_info = {
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.vref_delay_usecs = 100,
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@ -131,13 +140,121 @@ SPI设备必须管理以下两种类型内存：
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spi_register_board_info(spi_board_info, ARRAY_SIZE(spi_board_info));
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```
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### 非静态定义
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#### DTS动态定义
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使用`spi_busnum_to_master()`查找目标SPI控制器；
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使用`spi_new_device()`创建;
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使用`spi_unregister_device()`销毁；
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##### Master
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### SPI Controller Driver
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```dts
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#---- build/boards/default/dts/cv181x/cv181x_base.dtsi
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/ {
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spi3:spi3@041B0000 {
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interrupts = <57 IRQ_TYPE_LEVEL_HIGH>;
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interrupt-parent = <&plic0>;
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};
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...
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```
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##### Slave
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- 独占总线
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```dts
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#---- build/boards/default/dts/cv181x/cv181x_asic_bga.dtsi
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&spi3 {
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status = "okay";
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num-cs = <1>;
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spidev@0 {
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compatible = "rohm,dh2228fv";
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spi-max-frequency = <1000000>;
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reg = <0>;
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};
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};
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#---- build/boards/cv181x/cv1813h_milkv_duos_sd/dts_riscv/cv1813h_milkv_duos_sd.dts
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&spi3 {
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status = "okay";
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spidev@0 {
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status = "okay";
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};
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};
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```
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- 多设备
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参考内核文档：
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1. linux_5.10/Documentation/devicetree/bindings/spi/spi-bus.txt；
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2. linux_5.10/arch/arm/boot/dts/imx6ul-imx6ull-opos6uldev.dtsi
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```dts
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#---- linux_5.10/arch/arm/boot/dts/imx6ull-opos6uldev.dts
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/dts-v1/;
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#include "imx6ull-opos6ul.dtsi" # 1
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# include "imx6ul.dtsi" # 1.1
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#include "imx6ul-imx6ull-opos6uldev.dtsi" # 2
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/ {
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model = "Armadeus Systems OPOS6UL SoM (i.MX6ULL) on OPOS6ULDev board";
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compatible = "armadeus,imx6ull-opos6uldev", "armadeus,imx6ull-opos6ul", "fsl,imx6ull";
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};
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#1.1- linux_5.10/arch/arm/boot/dts/imx6ul.dtsi
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/ {
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...
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soc {
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...
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aips1: bus@2000000 {
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...
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spba-bus@2000000 {
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...
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ecspi4: spi@2014000 {
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#address-cells = <1>;
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#size-cells = <0>;
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compatible = "fsl,imx6ul-ecspi", "fsl,imx51-ecspi";
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reg = <0x02014000 0x4000>;
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interrupts = <GIC_SPI 34 IRQ_TYPE_LEVEL_HIGH>;
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clocks = <&clks IMX6UL_CLK_ECSPI4>,
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<&clks IMX6UL_CLK_ECSPI4>;
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clock-names = "ipg", "per";
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dmas = <&sdma 9 7 1>, <&sdma 10 7 2>;
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dma-names = "rx", "tx";
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status = "disabled";
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};
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#2--- linux_5.10/arch/arm/boot/dts/imx6ul-imx6ull-opos6uldev.dtsi
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&ecspi4 {
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pinctrl-names = "default";
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pinctrl-0 = <&pinctrl_ecspi4>;
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num-cs = 2;
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cs-gpios = <&gpio4 9 GPIO_ACTIVE_LOW>, <&gpio4 3 GPIO_ACTIVE_LOW>;
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status = "okay";
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spidev0: spi@0 {
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compatible = "spidev";
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reg = <0>;
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spi-max-frequency = <5000000>;
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};
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spidev1: spi@1 {
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compatible = "spidev";
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reg = <1>;
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spi-max-frequency = <5000000>;
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};
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};
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```
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#### 总结
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1. `spi-max-frequency`，多通道时，需要定义设备允许的最大速率；---- 待确认；
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### 驱动
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- `spi_busnum_to_master()`, 查找目标SPI控制器；
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- `spi_new_device()`, 创建;
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- `spi_unregister_device()`销毁；
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#### SPI Controller Driver
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```c
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struct spi_master *master;
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@ -152,14 +269,14 @@ SPI设备必须管理以下两种类型内存：
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- `spi_[un]register_master()`注册至系统；
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#### 接口
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master操作集
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- `master->setup(struct spi_device *spi)`, clock rate, SPI mode, and word sizes.
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- `master->cleanup(struct spi_device *spi)`, 清除之前由`spi_device.controller_state`锁定的状态；
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...
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...
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- `master->transfer_one_message(struct spi_master *master, struct spi_message *mesg)`, 发送一个mesg；
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### SPI Protocol Driver
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#### SPI Protocol Driver
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```c
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static int CHIP_probe(struct spi_device *spi)
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@ -193,7 +310,9 @@ SPI设备必须管理以下两种类型内存：
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.remove = CHIP_remove,
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};
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```
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spi_setup(),
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## 属性
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- `spi_message.is_dma_mapped`，
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@ -53,7 +53,7 @@ static const struct of_device_id CHIP_of_match[] = {
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{ }
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};
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MODULE_DEVICE_TABLE(of, CHIP_of_match);
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MODULE_DEVICE_TABLE(of, CHIP_of_match); // Used by file2alias, which indicated what devices are support with this drive.
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#endif // CONFIG_OF
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static struct spi_driver CHIP_driver = {
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