Linux内核-音频驱动移植

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FarSight（讨论 | 贡献）2020年7月28日 (二) 16:41的版本 （→‎实验原理）

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实验原理

FS-MP1A使用的是CS42L51音频芯片，SoC通过I2C和SAI与其进行数据交互，原理图如下：

57-1-1-1.png

SAI2管脚对应关系：

57-1-1-2.png

57-1-1-3.png

57-1-1-4.png

I2C5管脚对应关系：

57-1-1-5.png

芯片复位管脚对应关系：

57-1-1-6.png

原理图网络编号 对应管脚 管脚功能 管脚功能码
SAI2_MCLKA PE0 SAI2_MCLK_A AF10
SAI2_SDB PF11 SDA2_SD_B AF10
SAI2_SCKA PI5 SAI2_SCK_A AF10
SAI_SDA PI6 SAI2_SD_A AF10
SAI2_FSA PI7 SAI2_FS_A AF10
AUDIO_RST PC0 IO ANALOG
I2C5_SDA PA11 I2C5_SDA AF4
I2C5_SCL PA12 I2C5_SDA AF4
  • SAI2设备树节点

参考文档： 

Documentation/devicetree/bindings/sound/st,stm32-sai.txt

内核中ST对STM32MP15x系列芯片的设备树资源了做了定义，可参见： 

sai2: sai@4400b000 {
	compatible = "st,stm32h7-sai";
	#address-cells = <1>;
	#size-cells = <1>;
	ranges = <0 0x4400b000 0x400>;
	reg = <0x4400b000 0x4>, <0x4400b3f0 0x10>;
	interrupts = <GIC_SPI 91 IRQ_TYPE_LEVEL_HIGH>;
	resets = <&rcc SAI2_R>;
	status = "disabled";

	sai2a: audio-controller@4400b004 {
		#sound-dai-cells = <0>;
		compatible = "st,stm32-sai-sub-a";
		reg = <0x4 0x1c>;
		clocks = <&rcc SAI2_K>;
		clock-names = "sai_ck";
		dmas = <&dmamux1 89 0x400 0x01>;
		status = "disabled";
	};

	sai2b: audio-controller@4400b024 {
		#sound-dai-cells = <0>;
		compatible = "st,stm32-sai-sub-b";
		reg = <0x24 0x1c>;
		clocks = <&rcc SAI2_K>;
		clock-names = "sai_ck";
		dmas = <&dmamux1 90 0x400 0x01>;
		status = "disabled";
	};
};

上述代码只对SAI2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。

参考stm32mp15xx-dkx.dtsi对于SAI2设备节点的描述，增加SAI2内容如下： 

&sai2 {
	clocks = <&rcc SAI2>, <&rcc PLL3_Q>, <&rcc PLL3_R>;
	clock-names = "pclk", "x8k", "x11k";
	pinctrl-names = "default", "sleep";
	pinctrl-0 = <&sai2a_pins_a>, <&sai2b_pins_b>;
	pinctrl-1 = <&sai2a_sleep_pins_a>, <&sai2b_sleep_pins_b>;
	status = "okay";

	sai2a: audio-controller@4400b004 {
		#clock-cells = <0>;
		dma-names = "tx";
		clocks = <&rcc SAI2_K>;
		clock-names = "sai_ck";
		status = "okay";

		sai2a_port: port {
			sai2a_endpoint: endpoint {
				remote-endpoint = <&cs42l51_tx_endpoint>;
				format = "i2s";
				mclk-fs = <256>;
				dai-tdm-slot-num = <2>;
				dai-tdm-slot-width = <32>;
			};
		};
	};

	sai2b: audio-controller@4400b024 {
		dma-names = "rx";
		st,sync = <&sai2a 2>;
		clocks = <&rcc SAI2_K>, <&sai2a>;
		clock-names = "sai_ck", "MCLK";
		status = "okay";

		sai2b_port: port {
			sai2b_endpoint: endpoint {
				remote-endpoint = <&cs42l51_rx_endpoint>;
				format = "i2s";
				mclk-fs = <256>;
				dai-tdm-slot-num = <2>;
				dai-tdm-slot-width = <32>;
			};
		};
	};
};

由于stm32mp15-pinctrl.dtsi中对于SAI2管脚的定义与FS-MP1A实际使用管脚一致，所以无需修改。

  • CS42L51设备树节点

由于前文中已经增加过I2C5的节点信息，本节就不再重复，在原有I2C5节点添加CS42L51内容即可。

参考文档： 

Documentation/devicetree/bindings/sound/cs42l51.txt

参考stm32mp15xx-dkx.dtsi对于codec芯片设备节点的描述，增加内容如下： 

cs42l51: cs42l51@4a {
	compatible = "cirrus,cs42l51";
	reg = <0x4a>;
	#sound-dai-cells = <0>;
	VL-supply = <&v3v3>;
	VD-supply = <&v1v8_audio>;
	VA-supply = <&v1v8_audio>;
	VAHP-supply = <&v1v8_audio>;
	reset-gpios = <&gpioc 0 GPIO_ACTIVE_LOW>;
	clocks = <&sai2a>;
	clock-names = "MCLK";
	status = "okay";

	cs42l51_port: port {
		#address-cells = <1>;
		#size-cells = <0>;

		cs42l51_tx_endpoint: endpoint@0 {
			reg = <0>;
			remote-endpoint = <&sai2a_endpoint>;
			frame-master;
			bitclock-master;
		};

		cs42l51_rx_endpoint: endpoint@1 {
			reg = <1>;
			remote-endpoint = <&sai2b_endpoint>;
			frame-master;
			bitclock-master;
		};
	};
};
  • 1.8V电源设备节点

前文已经说过如何添加电源节点，本节不再重复，在根节点添加&v1v8_audio节点，内容如下： 

v1v8_audio: regulator-v1v8_audio {
	compatible = "regulator-fixed";
	regulator-name = "v1v8_audio";
	regulator-min-microvolt = <1800000>;
	regulator-max-microvolt = <1800000>;
	regulator-always-on;
	regulator-boot-on;
};
  • SOC声卡驱动节点

内核中包含audio-graph-card驱动，驱动将声卡各个部分关联起来，驱动正常工作需添加对应设备树节点。

参考文档： 

Documentation/devicetree/bindings/sound/audio-graph-card.txt

在根节点写下添加sound节点： 

sound {
	compatible = "audio-graph-card";
	label = "STM32MP1-FSMP1A";
	routing =
		"Playback" , "MCLK",
		"Capture" , "MCLK",
		"MICL" , "Mic Bias";
	dais = <&sai2a_port &sai2b_port>;
	status = "okay";
};

实验目的

熟悉基于Linux操作系统下的音频设备驱动移植配置过程。

实验平台

华清远见开发环境，FS-MP1A平台；

实验步骤

  • 添加SAI2节点

修改arch/arm/dts/stm32mp15xx-fsmp1x.dts文件，在文件末尾添加如下内容： 

&sai2 {
	clocks = <&rcc SAI2>, <&rcc PLL3_Q>, <&rcc PLL3_R>;
	clock-names = "pclk", "x8k", "x11k";
	pinctrl-names = "default", "sleep";
	pinctrl-0 = <&sai2a_pins_a>, <&sai2b_pins_b>;
	pinctrl-1 = <&sai2a_sleep_pins_a>, <&sai2b_sleep_pins_b>;
	status = "okay";

	sai2a: audio-controller@4400b004 {
		#clock-cells = <0>;
		dma-names = "tx";
		clocks = <&rcc SAI2_K>;
		clock-names = "sai_ck";
		status = "okay";

		sai2a_port: port {
			sai2a_endpoint: endpoint {
				remote-endpoint = <&cs42l51_tx_endpoint>;
				format = "i2s";
				mclk-fs = <256>;
				dai-tdm-slot-num = <2>;
				dai-tdm-slot-width = <32>;
			};
		};
	};

	sai2b: audio-controller@4400b024 {
		dma-names = "rx";
		st,sync = <&sai2a 2>;
		clocks = <&rcc SAI2_K>, <&sai2a>;
		clock-names = "sai_ck", "MCLK";
		status = "okay";

		sai2b_port: port {
			sai2b_endpoint: endpoint {
				remote-endpoint = <&cs42l51_rx_endpoint>;
				format = "i2s";
				mclk-fs = <256>;
				dai-tdm-slot-num = <2>;
				dai-tdm-slot-width = <32>;
			};
		};
	};
};
  • 添加CS42L51节点

修改arch/arm/dts/stm32mp15xx-fsmp1x.dts文件，在I2C5节点中添加如下内容： 

cs42l51: cs42l51@4a {
	compatible = "cirrus,cs42l51";
	reg = <0x4a>;
	#sound-dai-cells = <0>;
	VL-supply = <&v3v3>;
	VD-supply = <&v1v8_audio>;
	VA-supply = <&v1v8_audio>;
	VAHP-supply = <&v1v8_audio>;
	reset-gpios = <&gpioc 0 GPIO_ACTIVE_LOW>;
	clocks = <&sai2a>;
	clock-names = "MCLK";
	status = "okay";

	cs42l51_port: port {
		#address-cells = <1>;
		#size-cells = <0>;

		cs42l51_tx_endpoint: endpoint@0 {
			reg = <0>;
			remote-endpoint = <&sai2a_endpoint>;
			frame-master;
			bitclock-master;
		};

		cs42l51_rx_endpoint: endpoint@1 {
			reg = <1>;
			remote-endpoint = <&sai2b_endpoint>;
			frame-master;
			bitclock-master;
		};
	};
};
  • 添加v1v8_audio电源节点

修改arch/arm/dts/stm32mp15xx-fsmp1x.dts文件，在根节点中添加如下内容： 

v1v8_audio: regulator-v1v8_audio {
	compatible = "regulator-fixed";
	regulator-name = "v1v8_audio";
	regulator-min-microvolt = <1800000>;
	regulator-max-microvolt = <1800000>;
	regulator-always-on;
	regulator-boot-on;
};
  • 添加Sound节点

修改arch/arm/dts/stm32mp15xx-fsmp1x.dts文件，在根节点中添加如下内容： 

sound {
	compatible = "audio-graph-card";
	label = "STM32MP1-FSMP1A";
	routing =
		"Playback" , "MCLK",
		"Capture" , "MCLK",
		"MICL" , "Mic Bias";
	dais = <&sai2a_port &sai2b_port>;
	status = "okay";
};
  • 配置内核

由于内核源码默认配置以及支持CS42L51，本节列出主要选项，如下： 

linux@ubuntu:$ make menuconfig
Device Drivers  --->
	<*> Sound card support  --->
		<*>   Advanced Linux Sound Architecture  --->
			<*>   ALSA for SoC audio support  --->
				STMicroelectronics STM32 SOC audio support  --->
					<*> STM32 SAI interface (Serial Audio Interface) support
					CODEC drivers  --->
						<*> Cirrus Logic CS42L51 CODEC (I2C)
				<*>   ASoC Audio Graph sound card support
  • 编译内核及设备树
linux@ubuntu:$ make -j4 uImage dtbs LOADADDR=0xC2000040
  • 重启测试

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，启动后启动信息中出现如下内容：

57-1-4-1.png

插上耳机，终端输入录音命令： 

root@fsmp1a:# arecord -D record_codec -f S16_LE -d 10 test.wav

终端输入播放命令： 

root@fsmp1a:# aplay test.wav

注意：由于3.5mm的4段式耳机接口还分为两种，一种是美标版（CTIA），也称为“苹果标准”，同时小米、魅族也是使用这种标准；另外一种是国标版（OMTP），也称为“诺基亚标准”，现在绝大多数诺基亚和大多数国产手机都是使用这种标准。FS_MP1A使用的是国标版，所以部分耳机并不能正常实现录播功能。

取自“http://wiki.farsightdev.com/index.php?title=Linux内核-音频驱动移植&oldid=216”