[alsa-devel] [Alsa-user] Jetway j7f2 via82xx volume problem: sound suddenly stops when increasing volume: "SOLVED" (well ... sort of)
tiwai at suse.de
Tue Apr 29 14:53:32 CEST 2008
At Mon, 28 Apr 2008 23:39:04 +0200,
Zoilo Gomez wrote:
> (Sorry for cross-posting from alsa-user; however, on 2nd thought I think
> this really belongs in alsa-devel):
> I think I have found what is causing this problem: in ac97_patch.c / int
> patch_vt1617a(...) there is a line of code:
> >>> snd_ac97_write_cache(a97, 0x5c, 0x20);
> According to a comment, this code is supposed to "bring the analog power
> consumption to normal, like WinXP driver for EPIA SP".
> If I comment out this line, the problem appears to be solved ... I can
> now put all volume controls to maximum values and the sound will keep
Appreciated that you hunted it out.
Added Cc to the patch author.
> This is consistent with the apparent introduction of this bug in kernel
> 2.6.19 (includes alsa-driver version 1.0.12rc1): no such problem
> occurred until 2.6.18, but all kernels since 2.6.19 do suffer from this
> problem. The line of code above first shows up in linux-2.6.19.
> Unfortunately, since I do not have a datasheet for the VT1617A chip set,
> I cannot verify the exact semantics, or suggest an improvement.
> Can anyone with a datasheet please suggest a proper patch to this line
> of code?
The register 0x5c is the VIA specific one. I have a VT1617 (without
A) datasheet, and it suggests that the bit corresponds to the
"headphone amplifier temperature sensing control". And setting this
bit means to _disable_ the temperature sensing control. This sounds
rather the correct to set.
However, I don't know whether any difference exists betweeen VIA1617
and 1617A although the codec id of both are identical.
Andrey, any comments about your patch?
In anyway, it'd be helpful if we can know which ac97 registers work
and wich not. Please take /proc/asound/card0/codec97#*/ac97#*-regs
file in both working and non-working cases to compare. Especially,
the registers 0x5a and 0x5c look interesting.
> Zoilo Gomez wrote:
> > In the mean time I have found that kernels 2.6.15 and 2.6.16 do not
> > suffer from this problem, whereas 2.6.22 till 2.6.25 do.
> > Testing for kernels 2.6.17 till 2.6.21 is somewhat complicated in my
> > setup, because there are other problems (NFS-related) which I need to
> > sort out.
> > So it looks like there is a bug somehow.
> > Providing the dxs_support parameter does not make any difference, no
> > matter what value I set it to.
> > Z.
> > Zoilo Gomez wrote:
> >> I have several J7F2 boards from Jetway, containing a 8237 via sound
> >> device on the south bridge.
> >> Using the alsa-driver, when I increase the volume then at some point
> >> all over sudden the sound stops. On some boards this happens at 75%,
> >> on others already at 60%, or 90%. Bringing the volume down again does
> >> not bring the audio back ...
> >> I am using the alsa-drivers with MPlayer.
> >> Although to me this smells like a hardware problem, I understand from
> >> googling around that this can be fixed with software, but I cannot
> >> find the correct solution anywhere. I have tested with gentoo kernels
> >> 2.6.22 and 2.6.24.
> >> AFAIK there are only 2 ways to get the sound back once it has stopped:
> >> 1) reset the mobo
> >> 2) rmmod snd-via82xx, followed by modprobe snd-via82xx
> >> The strange thing is that in option 2), the problem seems to be gone
> >> once the driver has been reloaded; from that moment on it is working
> >> fine ....!
> >> There is a driver from Via Arena (viaudiocombo) that seems to work
> >> fine, but it is OSS i.o. ALSA, and also a development by Via Arena
> >> i.o. the Linux community. Besides, I need synchronization features
> >> from the audio driver, and I do not think that OSS support this (not
> >> 100% sure).
> >> Can anyone help me and shed light on this?
> >> TIA!
> >> Zoilo.
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