[alsa-devel] Bugs on aspire one A150

Maxim Levitsky maximlevitsky at gmail.com
Sat Nov 22 20:00:18 CET 2008

Maxim Levitsky wrote:
> Andreas Mohr wrote:
>> Hi,
>> On Wed, Nov 12, 2008 at 07:07:04PM +0200, Maxim Levitsky wrote:
>>> I pretty much studied the datasheet and driver, and this is what I 
>>> found:
>>> btw, my acer 5720 and aspire one share same ALC268.
>>> Some stuff is trivially fixable, some seems to be unfixable at all:
>> Wow, what an extremely in-depth analysis!
>> I just intended to dive into getting mic routing corrected myself,
>> thus you saved me a lot of time!
>>> model=acer is used on my regular laptop.
>>> model-acer-aspire is used on aspire one laptop, and it needs to be 
>>> renamed, as both are aspire.
>> +1 (your analysis of both being rather different - as already pondered -
>> confirms this necessity)
>>> And now for unfixable problems:
>>> 1) There is strong DC offset on all inputs.
>>> it is even different on left/right and depends on capture volume.
>>> I tried to change the VREF only param that could help, but it doesn't.
>>> I feel that this is hardware flaw.
>>> (It is possible that voltage on inputs is created by circuit made by 
>>> acer, and then ALC268 amplifies it.)
>> Sounds like really bad circuit design then.
>> One would think that the Intel HDA architecture might have builtin
>> measures to compensate for this if needed? DC offset issues on
>> soundcards aren't exactly a new phenomenon after all...
>>> Lastly I noticed that datasheet mentions so called 'coefficients':
>>> the codecs exposes lots of internal and undocumented registers using 
>>> set address/ get/set value scheme.
>>> maybe some of above bugs are fixable there, but ether realtek has to 
>>> provide data for that or reverse engineering of
>>> windows driver is required.
>> I've actually had a peek at the .inf files since I thought that it would
>> already contain register values in those registry keys that it creates on
>> install, but yeah, that's all in-driver it seems.
>> Probably time to ask Acer about specifics, especially since I didn't spot
>> any hda-intel changes in their linux- source.
>> Thank you very much,
>> Andreas Mohr
> Small update:
> 1) The dc offset isn't present on aspire one, really is a circuit design 
> bug I guess 2) Internal mic works perfectly on aspire one, can reproduce 
> the strange behaver at all,
> Probably this was mixer bug.
Finally, I found how to reproduce that bug,
I mean to get normal volume on internal mic, I have to increase volume
only on left or right channel.

So, this happens always, and _only_ when recording _mono_ sound from internal

Since hardware doesn't support hardware mono input, tested with -D hw:0
I suspect this to be alsa-lib bug, any ideas?
Happens with arecord -D plughw:0 -c1 .

Best regards,
	Maxim Levitsky

> So aspire one support is almost, only need to add support to restore 
> beep volume
> after resume.
> Best regards,
>     Maxim Levitsky

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