Re: [PATCH v2] ALSA: hda/realtek: Enable PC beep passthrough for HP EliteBook 855 G7

[Jaroslav Kysela <perex@xxxxxxxx>]

On 17. 02. 25 11:02, Takashi Iwai wrote:
> On Sun, 16 Feb 2025 22:31:03 +0100,
> Maciej S. Szmigiero wrote:
> > PC speaker works well on this platform in BIOS and in Linux until sound
> > card drivers are loaded. Then it stops working.
> >
> > There seems to be a beep generator node at 0x1a in this CODEC
> > (ALC269_TYPE_ALC215) but it seems to be only connected to capture mixers
> > at nodes 0x22 and 0x23.
> > If I unmute the mixer input for 0x1a at node 0x23 and start recording
> > from its "ALC285 Analog" capture device I can clearly hear beeps in that
> > recording.
> >
> > So the beep generator is indeed working properly, however I wasn't able to
> > figure out any way to connect it to speakers.
> >
> > However, the bits in the "Passthrough Control" register (0x36) seems to
> > work at least partially: by zeroing "B" and "h" and setting "S" I can at
> > least make the PIT PC speaker output appear either in this laptop speakers
> > or headphones (depending on whether they are connected or not).
> >
> >
> > There are some caveats, however:
> > * If the CODEC gets runtime-suspended the beeps stop so it needs HDA beep
> > device for keeping it awake during beeping.
> >
> > * If the beep generator node is generating any beep the PC beep passthrough
> > seems to be temporarily inhibited, so the HDA beep device has to be
> > prevented from using the actual beep generator node - but the beep device
> > is still necessary due to the previous point.
> >
> > * In contrast with other platforms here beep amplification has to be
> > disabled otherwise the beeps output are WAY louder than they were on pure
> > BIOS setup.
> >
> >
> > Unless someone (from Realtek probably) knows how to make the beep generator
> > node output appear in speakers / headphones using PC beep passthrough seems
> > to be the only way to make PC speaker beeping actually work on this
> > platform.
> >
> > Signed-off-by: Maciej S. Szmigiero <mail@xxxxxxxxxxxxxxxxxxxxx>
> > ---
> >
> > Since more than 6 weeks has now passed since the previous version of this
> > patch was posted, yet no better or other solution was provided I'm
> > re-submitting an updated version of the original patch.
> >      
> > This solution has been working fine for me on this platform all that time,
> > without any obvious issues.
> >      
> > Changes from v1:
> > * Correct the typo in !IS_ENABLED(CONFIG_INPUT_PCSPKR) code that the
> > kernel test robot found.
> >      
> > * Change codec_warn() into dev_warn_once(hda_codec_dev(codec))
> > to avoid spamming the kernel log at runtime PM CODEC re-init.
>
> This is really a thing to be checked by Realtek people at first, as
> it's very vendor-specific thing.
>
> Kailang, please check this.

The primary issue seems to be with the beep signal routing to the analog 
outputs. The hidden codec registers accessed through the coefficient nodes may 
play a role for this setup. Only Realtek can give a solid answer for this 
(lack of public codec documentation).

					Jaroslav

--
Jaroslav Kysela <perex@xxxxxxxx>
Linux Sound Maintainer; ALSA Project; Red Hat, Inc.