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From:   "He, Bo" <bo.he@intel.com>
To:     "kailang@realtek.com" <kailang@realtek.com>,
        "alsa-devel@alsa-project.org" <alsa-devel@alsa-project.org>,
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        "hui.wang@canonical.com" <hui.wang@canonical.com>
Subject: audio lost from speaker after reboot from windows on the device
 ALC295
Thread-Topic: audio lost from speaker after reboot from windows on the
 device ALC295
Thread-Index: AdUyX8fMiuN0r83nQWCeaW0Sd+ObdQ==
Date:   Thu, 4 Jul 2019 12:02:17 +0000
Message-ID: <CD6925E8781EFD4D8E11882D20FC406D52AB58B6@SHSMSX104.ccr.corp.intel.com>
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Hi, patch_realtek.c maintainer:
	I see one issue that reboot from windows and boot to ubuntu, the audio lost from speaker, I suspect there are some bugs in patch_realtek.c drivers,  the device is ALC295 and the device id is 0x10ec0295.

I have done the below experiments:
1. reboot from windows to windows, the audio is persist .
2. reboot from windows to ubuntu, the audio lost from speaker, but can hear if I hotplug one earphone.
3. if the issue reproduce after reboot from windows, reboot the ubuntu can't restore the audio, I suspect it's warm reset.
4. if I write the port 0xcf9 with 0xe to do cold reset, the audio can restore.
5. if I do suspend/resume, the audio can restore, I suspect do cold boot and suspend will trigger the platform reset to reset the ALC295.
6. if I do double function reset (write the verb 0x7ff in alc_init), the audio is still can't restore.
snd_hda_codec_write(codec, 0x01, 0, AC_VERB_SET_CODEC_RESET, 0); /* Function reset */
snd_hda_codec_write(codec, 0x01, 0, AC_VERB_SET_CODEC_RESET, 0); /* double Function reset */
7. the issue is first found on kernel 4.19.50, I still see the issue with the latest kernel 5.2-rc2, is it possible windows change some default registers, but ALC295 don't initialize the register?