[RK3399][Android7.1] 调试笔记 --- HDMI输出没有音频信号

Platform: RK3399
OS: Android 7.1 industry
Kernel: v4.4.83

现象：
主屏使用HDMI,插入显示屏播放音乐，只有显示没有声音。

Log:
01-18 08:51:20.024 414 437 D AudioHardwareTiny: start_output_stream: the number of HDMI is invalid,please check

分析：
根据Log分析查到HDMI number号从下面函数中获取：

static void read_out_sound_card(struct stream_out *out){ while((size = get_line(file,buf,sizeof(buf))) >= 0){ ALOGD("%s: buf = %s",__FUNCTION__,buf); if(is_speaker_out_sound_card(buf)){ device->out_card[SND_OUT_SOUND_CARD_SPEAKER] = get_card_number(buf); }else if(is_hdmi_out_sound_card(buf)){ device->out_card[SND_OUT_SOUND_CARD_HDMI] = get_card_number(buf); }else if(is_spdif_out_sound_card(buf)){ device->out_card[SND_OUT_SOUND_CARD_SPDIF] = get_card_number(buf); }else if(is_bt_out_sound_card(buf)){ device->out_card[SND_OUT_SOUND_CARD_BT] = get_card_number(buf); } }}

关注HDMI获取部分：

static bool is_hdmi_out_sound_card(char* buf){ const char* NAME [] = { "rockchiphdmi", "rkhdmidpsound", };......}

也就是说需要是rockchiphdmi或者rkhdmidpsound名字的声卡才可以。

查看声卡设备信息：

rk3399_all:/ # cat /proc/asound/cards 0 [realtekrt5651co]: realtekrt5651co - realtekrt5651codec_hdmiin realtekrt5651codec_hdmiin 1 [HDMICODEC ]: HDMI-CODEC - HDMI-CODEC HDMI-CODEC

并没我们需要的，查看dts，发现codec里的card name写成了 “HDMI-CODEC”。(dts参考的是rk3399-firefly-android.dts)

hdmi_codec: hdmi-codec {compatible = "simple-audio-card";simple-audio-card,format = "i2s";simple-audio-card,mclk-fs = <256>;simple-audio-card,name = "HDMI-CODEC";simple-audio-card,cpu {sound-dai = <&i2s2>;};simple-audio-card,codec {sound-dai = <&hdmi>;};};

解决方法：
把“HDMI-CODEC”改成"rockchip,hdmi" 就能正常。

再查看就正常了：

rk3399_all:/ # cat /proc/asound/cards 0 [realtekrt5651co]: realtekrt5651co - realtekrt5651codec_hdmiin realtekrt5651codec_hdmiin 1 [rockchiphdmi ]: rockchip_hdmi - rockchip,hdmi rockchip,hdmi

参考：
HDMI_IN_开发指南_V1.1_20190226.pdf