背景

整個嵌入式專案由Buildroot構建，現有專案增加音訊TAS5754驅動,詳細步驟如下

Buildroot 配置

• 核心檔案配置

Kernel -> Defconfig name -> 核心配置檔名稱

• 核心DTS配置

Kernel -> Device Tree Source file name -> dts名稱

核心配置

核心中主要涉及DTS的配置,路徑arch/arm64/boot/dts/廠商/xxx.dts

#include "mesonaxg.dtsi"
/ {
	model = "Amlogic";
	amlogic-dt-id = "xxxx";  // 這個配置很重要，要和buildroot中Device Tree Source file name名稱一致
 

	sugr-case-id = "xxx";
	sugr-hw-id = "11";
	compatible = "xxx, xxx";
	interrupt-parent = <&gic>;
	#size-cells = <2>;

• DTS中晶片IIC配置

/* for spk board */
&i2c2 {
    status = "okay";
    pinctrl-names="default";
    pinctrl-0=<&c_i2c_master>;
    npcp215x_e6: [email protected]
 
 {
                 compatible = "nuvoton,npcp215x";
                 #sound-dai-cells = <0>;
                 reg = <0x73>;
                 status = "disable";   // 禁止
                 reset_pin = <&gpio_ao GPIOAO_4 0>;
                 mute_pin  = <&gpio_ao GPIOAO_3 0>;
                 amp_power =
 
 <&gpio_ao GPIOAO_7 0>;
             };
    tas575x_37: [email protected]37 {
                 compatible = "ti,tas575x"; //匹配名稱
                 #sound-dai-cells = <0>;
                 reg = <0x4e>;     //IIC從機裝置地址
                 status = "okay";  //使能
                 mute_pin  = <&gpio_ao GPIOAO_3 0>;  //引腳配置
                 amp_power = <&gpio_ao GPIOAO_7 0>;
             };
};

kernel/sound/soc/codecs/廠商/tas575x.c

//DTS 裝置匹配
static const struct of_device_id tas575x_of_match[] = {
	{ .compatible = "ti, tas5754", 0 },
	{ .compatible = "ti, tas5756", 0 },
	{ .compatible = "ti, tas575x", 0 },
	{ }
};

//i2c id 匹配
static const struct i2c_device_id tas575x_i2c_id[] = {
	{ "tas5754", (kernel_ulong_t) 0 },
	{ "tas5756", (kernel_ulong_t) 0 },
	{ "tas575x", (kernel_ulong_t) 0 },
	{ }
};

//DTS中配置的引腳通過該介面來操作
amp_power = of_get_named_gpio(node,"amp_power",0);
if (amp_power < 0){
    pr_err("%s fail to get mute pin from dts!\n", __func__);
}
gpio_direction_output(amp_power,GPIOF_OUT_INIT_HIGH);

• DTS中IIS配置

    aml-audio-card,dai-[email protected]2 {
        format = "i2s";
        mclk-fs = <256>;
        continuous-clock;
        /* tdmb clk using tdmc so no bclk-inv */
        //bitclock-inversion;
        //frame-inversion;
        bitclock-master = <&aml_tdmc>;
        frame-master = <&aml_tdmc>;
        cpu {
            sound-dai = <&aml_tdmc>;
            dai-tdm-slot-tx-mask = <1 1>;
            dai-tdm-slot-rx-mask = <1 1>;
            dai-tdm-slot-num = <2>;
            dai-tdm-slot-width = <32>;
            system-clock-frequency = <12288000>;
        };
        codec {
            //sound-dai = <&npcp215x_e6>;
            sound-dai = <&tas575x_37>;  //ALSA dai配置
        };
    };

IIS這裡的配置並沒有深入研究，後續需要會跟進

驗證音訊驅動

1. IIC通訊是否成功

static int tas575x_i2c_probe(struct i2c_client *client,const struct i2c_device_id *id)
{

	//const struct of_device_id *of_id;
	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
	if (!priv)
		return -ENOMEM;
	i2c_set_clientdata(client, priv);
	priv->regmap = devm_regmap_init_i2c(client, &tas575x_regmap);
	...
	return snd_soc_register_codec(dev, &soc_codec_dev_tas575x,
					  &tas575x_dai, 1);
}

需要注意一點：軟體中tas575x_i2c_probe匹配成功，IIC不一定通訊成功，需要實際驗證

2 . 相關功放引腳

檢視功放TAS5754資料手冊，MUTE需要拉高功放才能出聲，否則會處於靜音狀態

3. 音訊裝置節點是否掛載成功

• 成功建立裝置節點，包括播放，錄音裝置

• 通過aplay 列出所有音效卡和數字音訊裝置，熒光筆標註的地方代表已經識別到tas575x音效卡

• 音訊EQ配置

後續跟進

• 播放音訊 音訊驅動正常啟動之後，可以通過alsa-utils-1.1.3.tar.bz2中的提供的工具aplay播放音訊，看功放是否正常出聲音

aplay -Dhw:0,2 xxx.wav
-D : select PCM by name 
0 : 代表 card0   2: 代表 deveice 2

IIC除錯

除錯IIC過程中需要用到邏輯分析儀，這裡用Saleae logic,軟體下載地址,軟體全平臺覆蓋，非常方便，相關軟體資料見

連結: https://pan.baidu.com/s/1KbFhnSIsWD4bFwJoIk1yzw 提取碼: xav9

問題

1. 測試音訊驅動，用應用程式aplay播放wav檔案: aplay -Dhw:0,2 xxx.wav

aplay: main:788: audio open error: Device or resource busy 

主要由於其他程序佔用card 0 裝置