查看“Linux内核-eMMC驱动移植”的源代码

==实验原理==
参考原理图可知eMMC使用的是sdmmc2总线，当前所使用的设备树文件中没有sdmmc2的支持，所以需要增加相关内容才能正常驱动eMMC。<br>
[[Image:49-1-1-1.png|640px]] <br>

由于在使STM32MP1芯片很多管脚为多功能复用管脚，且很多管脚具备同样的功能，所以移植eMMC时需要确认硬件设计是使用的是那些管脚，根据原理图确认后管脚对应关系为：<br>
{|class="wikitable"
|-
! 原理图网络编号 !!对应管脚 !!管脚功能 !! 管脚功能码
|-
| SD2_DATA0 
| PB14 
| SDMMC2_D0
| AF9
|-
| SD2_DATA1 
| PB15 
| SDMMC2_D1
| AF9
|-
| SD2_DATA2 
| PB3 
| SDMMC2_D2
| AF9
|-
| SD2_DATA3 
| PB4 
| SDMMC2_D3
| AF9
|-
| SD2_DATA4 
| PA8 
| SDMMC2_D4
| AF9
|-
| SD2_DATA5 
| PA9 
| SDMMC2_D5
| AF10
|-
| SD2_DATA6 
| PE5 
| SDMMC2_D6
| AF9
|-
| SD2_DATA7 
| PD3 
| SDMMC2_D7
| AF9
|-
| SD2_CLK
| PE3 
| SDMMC2_CK
| AF9
|-
| SD2_CMD 
| PG6
| SDMMC2_CMD
| AF10
|}
<ol>
<li>eMMC设备树节点</li>
参考文档：
<pre><nowiki>
Documentation/devicetree/bindings/mmc/mmc-controller.yaml
Documentation/devicetree/bindings/mmc/mmci.txt
</nowiki></pre>
内核中ST对STM32MP15x系列芯片的设备树资源了做了定义，可参见：
 arch/arm/boot/dts/stm32mp151.dtsi
stm32mp151中sdmmc2定义如下：
<pre><nowiki>
sdmmc2: sdmmc@58007000 {
	compatible = "arm,pl18x", "arm,primecell";
	arm,primecell-periphid = <0x00253180>;
	reg = <0x58007000 0x1000>, <0x58008000 0x1000>;
	interrupts = <GIC_SPI 124 IRQ_TYPE_LEVEL_HIGH>;
	interrupt-names = "cmd_irq";
	clocks = <&rcc SDMMC2_K>;
	clock-names = "apb_pclk";
	resets = <&rcc SDMMC2_R>;
	cap-sd-highspeed;
	cap-mmc-highspeed;
	max-frequency = <120000000>;
	status = "disabled";
};
</nowiki></pre>
上述代码只对sdmmc2做了基本的初始化，并没有针对不同的硬件设计做适配，所以需结合硬件补全设备树节点信息。<br>

eMMC有8根数据线，且eMMC无需热插拔等功能，结合硬件信息添加sdmmc2节点信息，也可参考内核中其他设备树文件中相关描述，比如stm32mp15xx-edx.dtsi关于sdmmc2的描述符合我们的要求，内容如下：
<pre><nowiki>
&sdmmc2 {
	pinctrl-names = "default", "opendrain", "sleep";
	pinctrl-0 = <&sdmmc2_b4_pins_a &sdmmc2_d47_pins_a>;
	pinctrl-1 = <&sdmmc2_b4_od_pins_a &sdmmc2_d47_pins_a>;
	pinctrl-2 = <&sdmmc2_b4_sleep_pins_a &sdmmc2_d47_sleep_pins_a>;
	non-removable;
	no-sd;
	no-sdio;
	st,neg-edge;
	bus-width = <8>;
	vmmc-supply = <&v3v3>;
	vqmmc-supply = <&vdd>;
	mmc-ddr-3_3v;
	status = "okay";
};
</nowiki></pre>
<li>管脚定义</li>

在内核中STM32MP1默认管脚定义在文件arch/arm/dts/stm32mp15-pinctrl.dtsi中，查看文件中是否有需要的管脚定义：<br>

查看后确认有sdmmc2的管脚定义，且与FS-MP1A硬件使用情况一致，定义如下：
<pre><nowiki>
sdmmc2_b4_pins_a: sdmmc2-b4-0 {
		pins1 {
			pinmux = <STM32_PINMUX('B', 14, AF9)>, /* SDMMC2_D0 */
				 <STM32_PINMUX('B', 15, AF9)>, /* SDMMC2_D1 */
				 <STM32_PINMUX('B', 3, AF9)>, /* SDMMC2_D2 */
				 <STM32_PINMUX('B', 4, AF9)>, /* SDMMC2_D3 */
				 <STM32_PINMUX('G', 6, AF10)>; /* SDMMC2_CMD */
			slew-rate = <1>;
			drive-push-pull;
			bias-pull-up;
		};
		pins2 {
			pinmux = <STM32_PINMUX('E', 3, AF9)>; /* SDMMC2_CK */
			slew-rate = <2>;
			drive-push-pull;
			bias-pull-up;
		};
	};

	sdmmc2_b4_od_pins_a: sdmmc2-b4-od-0 {
		pins1 {
			pinmux = <STM32_PINMUX('B', 14, AF9)>, /* SDMMC2_D0 */
				 <STM32_PINMUX('B', 15, AF9)>, /* SDMMC2_D1 */
				 <STM32_PINMUX('B', 3, AF9)>, /* SDMMC2_D2 */
				 <STM32_PINMUX('B', 4, AF9)>; /* SDMMC2_D3 */
			slew-rate = <1>;
			drive-push-pull;
			bias-pull-up;
		};
		pins2 {
			pinmux = <STM32_PINMUX('E', 3, AF9)>; /* SDMMC2_CK */
			slew-rate = <2>;
			drive-push-pull;
			bias-pull-up;
		};
		pins3 {
			pinmux = <STM32_PINMUX('G', 6, AF10)>; /* SDMMC2_CMD */
			slew-rate = <1>;
			drive-open-drain;
			bias-pull-up;
		};
	};

	sdmmc2_b4_sleep_pins_a: sdmmc2-b4-sleep-0 {
		pins {
			pinmux = <STM32_PINMUX('B', 14, ANALOG)>, /* SDMMC2_D0 */
				 <STM32_PINMUX('B', 15, ANALOG)>, /* SDMMC2_D1 */
				 <STM32_PINMUX('B', 3, ANALOG)>, /* SDMMC2_D2 */
				 <STM32_PINMUX('B', 4, ANALOG)>, /* SDMMC2_D3 */
				 <STM32_PINMUX('E', 3, ANALOG)>, /* SDMMC2_CK */
				 <STM32_PINMUX('G', 6, ANALOG)>; /* SDMMC2_CMD */
		};
	};

	sdmmc2_b4_pins_b: sdmmc2-b4-1 {
		pins1 {
			pinmux = <STM32_PINMUX('B', 14, AF9)>, /* SDMMC2_D0 */
				 <STM32_PINMUX('B', 15, AF9)>, /* SDMMC2_D1 */
				 <STM32_PINMUX('B', 3, AF9)>, /* SDMMC2_D2 */
				 <STM32_PINMUX('B', 4, AF9)>, /* SDMMC2_D3 */
				 <STM32_PINMUX('G', 6, AF10)>; /* SDMMC2_CMD */
			slew-rate = <1>;
			drive-push-pull;
			bias-disable;
		};
		pins2 {
			pinmux = <STM32_PINMUX('E', 3, AF9)>; /* SDMMC2_CK */
			slew-rate = <2>;
			drive-push-pull;
			bias-disable;
		};
	};

	sdmmc2_b4_od_pins_b: sdmmc2-b4-od-1 {
		pins1 {
			pinmux = <STM32_PINMUX('B', 14, AF9)>, /* SDMMC2_D0 */
				 <STM32_PINMUX('B', 15, AF9)>, /* SDMMC2_D1 */
				 <STM32_PINMUX('B', 3, AF9)>, /* SDMMC2_D2 */
				 <STM32_PINMUX('B', 4, AF9)>; /* SDMMC2_D3 */
			slew-rate = <1>;
			drive-push-pull;
			bias-disable;
		};
		pins2 {
			pinmux = <STM32_PINMUX('E', 3, AF9)>; /* SDMMC2_CK */
			slew-rate = <2>;
			drive-push-pull;
			bias-disable;
		};
		pins3 {
			pinmux = <STM32_PINMUX('G', 6, AF10)>; /* SDMMC2_CMD */
			slew-rate = <1>;
			drive-open-drain;
			bias-disable;
		};
	};

	sdmmc2_d47_pins_a: sdmmc2-d47-0 {
		pins {
			pinmux = <STM32_PINMUX('A', 8, AF9)>, /* SDMMC2_D4 */
				 <STM32_PINMUX('A', 9, AF10)>, /* SDMMC2_D5 */
				 <STM32_PINMUX('E', 5, AF9)>, /* SDMMC2_D6 */
				 <STM32_PINMUX('D', 3, AF9)>; /* SDMMC2_D7 */
			slew-rate = <1>;
			drive-push-pull;
			bias-pull-up;
		};
	};

	sdmmc2_d47_sleep_pins_a: sdmmc2-d47-sleep-0 {
		pins {
			pinmux = <STM32_PINMUX('A', 8, ANALOG)>, /* SDMMC2_D4 */
				 <STM32_PINMUX('A', 9, ANALOG)>, /* SDMMC2_D5 */
				 <STM32_PINMUX('E', 5, ANALOG)>, /* SDMMC2_D6 */
				 <STM32_PINMUX('D', 3, ANALOG)>; /* SDMMC2_D7 */
		};
	};
</nowiki></pre>
</ol>

==实验目的==
熟悉基于Linux操作系统下的块设备驱动移植配置过程。<br>
==实验平台==
华清远见开发环境，FS-MP1A平台；<br>
==实验步骤==
*添加eMMC设备树配置<br>

修改arch/arm/dts/stm32mp15xx-fsmp1x.dts文件<br>

在原有sdmmc1节点下添加如下内容：
<pre><nowiki>
&sdmmc2 {
	pinctrl-names = "default", "opendrain", "sleep";
	pinctrl-0 = <&sdmmc2_b4_pins_a &sdmmc2_d47_pins_a>;
	pinctrl-1 = <&sdmmc2_b4_od_pins_a &sdmmc2_d47_pins_a>;
	pinctrl-2 = <&sdmmc2_b4_sleep_pins_a &sdmmc2_d47_sleep_pins_a>;
	non-removable;
	no-sd;
	no-sdio;
	st,neg-edge;
	bus-width = <8>;
	vmmc-supply = <&v3v3>;
	vqmmc-supply = <&vdd>;
	mmc-ddr-3_3v;
	status = "okay";
};
</nowiki></pre>
*配置内核<br>

由于内核源码默认配置已经支持eMMC，本节列出主要选项，如下：
<pre><nowiki>
linux@ubuntu:$ make menuconfig
Device Drivers  --->
	<*> MMC/SD/SDIO card support  --->
	[*]     STMicroelectronics STM32 SDMMC Controller
</nowiki></pre>
*编译内核级设备树：
 linux@ubuntu:$ make -j4 uImage dtbs LOADADDR=0xC2000040
*重启测试<br>

将编译好的设备树和内核镜像拷贝到/tftpboot目录下，通过tftp引导内核，重启设备后可以看到如下启动信息：

[[Image:49-1-4-1.png]] <br>

由于eMMC中有出厂预装的FS-MP1A系统，所以可以正常完成文件系统挂载进入系统：

[[Image:49-1-4-2.png]] <br>