Re: audio lost from speaker after reboot from windows on the device ALC295

[Hui Wang]

Maybe your machine has an external amplifier which needs to be set by 
software before it can work.

On 2019/7/4 äå8:02, He, Bo wrote:
> 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?