[Linux Audio Driver] Solve line-out output is unstable

最新推荐文章于 2023-07-18 17:47:54 发布

原创最新推荐文章于 2023-07-18 17:47:54 发布 · 902 阅读

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本文介绍了一种在硬件引擎测试扬声器功率时遇到的音频信号不稳定问题，并详细阐述了解决该问题的方法，即通过调整Qualcomm设计中的硬件延迟来稳定信号。

Recently i experience some thing and want to improve my English， so i will try to use English to write the new document completely.

0. background

OK, let’s go straight to the topic. We will found the line-out output singal is not stable, while the hardware engineer test the speaker power.

The problem is confused and unbelievable.

在这里插入图片描述

1. Solution

The key problem that causes this problem is the HW delay. Qualcomm design is adapted to their own wsa pa. When we use the third party PA, we need to change to HW delay to stabilize the singal .

code path as sample:

./kernel/msm-3.18/sound/soc/codecs/msm8x16-wcd.c

static int msm8x16_wcd_lo_dac_event(struct snd_soc_dapm_widget *w,
	struct snd_kcontrol *kcontrol, int event)
{
	struct snd_soc_codec *codec = w->codec;

	dev_dbg(codec->dev, "%s %s %d\n", __func__, w->name, event);

	switch (event) {
	case SND_SOC_DAPM_PRE_PMU:
        ...
		msleep(5);
		break;
	case SND_SOC_DAPM_POST_PMU:
		snd_soc_update_bits(codec,
			MSM8X16_WCD_A_ANALOG_RX_LO_DAC_CTL, 0x80, 0x80);
		snd_soc_update_bits(codec,
			MSM8X16_WCD_A_ANALOG_RX_LO_DAC_CTL, 0x08, 0x00);
		snd_soc_update_bits(codec,
			MSM8X16_WCD_A_ANALOG_RX_LO_EN_CTL, 0x40, 0x40);
		msleep(20);//value is adjustable
		break;
	case SND_SOC_DAPM_POST_PMD:
        ...
		break;
	}
	return 0;
}

2. Author Note

/******
@article{Linux Audio Driver,
Author = { 1byte ≠ 8bit},
Year = { 2021},
}
******/