Bug 496119

I am seeing this on rawhide kernel 2.6.29.1-100.fc11.i586 running inside VirtualBox 2.2.0 OSE on Mac OS X, where ALSA sound output is unusable (skips all the time), presumably because of this. This started happening when I upgraded my kernel.

I tried with an older kernel which does not have audible sound problems, and that kernel also had trouble measuring the clock. So my issue may be unrelated.

It seems that hardware requires more delay before access, please, try this patch:

http://git.alsa-project.org/?p=alsa-kmirror.git;a=commitdiff;h=0209d72d70ffd7405d6f1b0036fed5e84c6cc9fe

That patch definitely seems to help with the ac97_clock measurement:

intel8x0_measure_ac97_clock: measured 50852 usecs (11 samples)
intel8x0: measured clock 216 rejected
intel8x0_measure_ac97_clock: measured 50959 usecs (2456 samples)
intel8x0: clocking to 48000

The hw_ptr messages and occasional sound stuttering persist. But if the clock measurement is now correct, then it isn't the cause of the hw_ptr skipping. Perhaps we need (another!) new bug for that.

The hw_ptr messages are really suspicious in this case.

Could you add some printk's to this portion of code in intel8x0.c?

        if (ptr1 != 0) {
                ptr1 <<= ichdev->pos_shift;
                ptr = ichdev->fragsize1 - ptr1;
                ptr += position;
                ichdev->last_pos = ptr;
                ichdev->last_pos_jiffies = jiffies;
        } else {
                ptr1 = jiffies - ichdev->last_pos_jiffies;
                if (ptr1)
                        ptr1 -= 1;
                ptr = ichdev->last_pos + ptr1 * ichdev->jiffy_to_bytes;

                printk("ptr1 = %u, last_pos = %u, jiffy_to_bytes = %u\n",
                             ptr1, ichdev->last_pos, ichdev->jiffy_to_bytes);

                ptr %= ichdev->size;
        }

I don't see how final ptr can be zero in this code.

This bug appears to have been reported against 'rawhide' during the Fedora 11 development cycle.
Changing version to '11'.

More information and reason for this action is here:
http://fedoraproject.org/wiki/BugZappers/HouseKeeping

This problem still occurs on Fedora 11 with kernel-2.6.29.4-167.fc11.i586.

This problem appears to be the same as described in 441087 and 444316.

The same circumvention as described towards the ends of 441087 and 444316
also works on Fedora 11 with kernel-2.6.29.4-167.fc11.i586  (except that
the old file name  modprobe.conf.dist  is called  dist.conf  in Fedora 11).

Bob, attach output from 'alsa-info.sh --no-upload' script and post ALSA driver error/warning messages from 'dmesg' or '/var/log/messages'.

Created attachment 348078 [details]
Output from  "alsa-info.sh --no-upload"  from "vanilla" Fedora 11 system.

Jaroslav,  The circumvention  (from 441087 and 444316)  for this bug was
removed, and the system re-booted, before running "alsa-info.sh --no-upload",
so the attached file "alsa-info.txt" reflects a "vanilla" Fedora 11 system.

The error/warning messages  (without the circumvention)  are as follows:
   intel8x0_measure_ac97_clock: measured 50929 usecs
   intel8x0: measured clock 78 rejected
   intel8x0: clocking to 48000

Please also note that bugs 441087 and 444316 were fixed in Fedora 10 by
kernel-2.6.27.12-170.2.5.fc10.i686.  The bug has re-appeared in Fedora 11.

I'm seeing the same problem since yesterday, when I upgraded the system which included alsa-plugins-pulseaudio-1.0.20-2.fc11.i58 (I don't know if it is related).
That playback is faster than it should (a 4:14 minutes song played in 3:57).

According to the logs, earlier kernels set ac97_clock to 
intel8x0: clocking to 48000
but yesterday it was set to
intel8x0: clocking to 51548

Forcing ac97_clock=48000, as described in #441087, fixes the problem here.

On my system, this problem seems to have been improved by  (or at least
affected by)  kernel-PAE-2.6.29.5-191.fc11.i686.  dmesg now shows:

     intel8x0_measure_ac97_clock: measured 50888 usecs (4 samples)
     intel8x0: measured clock 78 rejected
     intel8x0_measure_ac97_clock: measured 50948 usecs (2852 samples)
     intel8x0: clocking to 41159

While these messages do not seem to be quite 100% kosher, YouTube videos
do now play at the correct speed, whereas they played too fast before.

(Btw, is it conceivable that this improvement might be a by-product of the
 fix for bug 506075, which was built into the above-mentioned kernel?)

Very sorry, the kernel in the previous comment is a typographical error.
It should have read  kernel-PAE-2.6.30.5-43.fc11.i686, which is new.
Very sorry for the confusion.

Further to Comment #11 and Comment #12, kernel-PAE-2.6.30.8-64.fc11.i686
shows further improvement  (compared to kernel-PAE-2.6.30.5-43.fc11.i686):

     intel8x0_measure_ac97_clock: measured 50429 usecs (2824 samples)
     intel8x0: clocking to 41143

(Now just these two messages, instead of the four messages produced by
kernel-PAE-2.6.30.5-43.fc11.i686, which appeared to take two attempts.)

As far as my system is concerned, this Bug is fixed, and could be closed.

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