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Date: Wed, 05 Dec 2001 18:51:18 -0500
From: Doug Ledford <dledford@redhat.com>
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To: Nathan Bryant <nbryant@optonline.net>
CC: Mario Mikocevic <mozgy@hinet.hr>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: i810 audio patch
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Nathan Bryant wrote:

> Doug Ledford wrote:
> 
>> Can you add a debug check to update_lvi()?  Something like:
>>
>> #ifdef DEBUG_MMAP
>>         if (dmabuf->count > dmabuf->fragsize && inb(port+OFF_CIV) == x)
>>                 printk(KERN_DEBUG,"i810_audio: update_lvi - CIV == 
>> LVI\n");
>> #endif
>>
>> and see if that triggers with the original mmap code? 
> 
> 
> I've narrowed it down a little more.. the above does not trigger. but 
> i've added some other printk's and the sequence of events goes like this:
> 
> open, mmap
> SETTRIGGER : works properly with the resync_dma removed; count 
> initialized to 65536
> we take 6 interrupts; 4 comp + lvi + dch; count drains to 0 properly
> [quake finishes initializing]
> GETOPTR:
> at the beginning of the call, count is 0; by the end of the call, count 
> has been set to 64K
> 
> but, we take no interrupts after this point.
> 

In __i810_update_lvi(), try changing the line that reads:

x = (dmabuf->dmasize + dmabuf->swptr - 1) % dmabuf->dmasize;

to use - 2 instead of -1 and see if that solves the problem (I've been 
suspecting an off-by-one error, I just haven't found it for sure.  The 
whole 65536 vs. 0 could be providing the off-by-one though.)

-- 

  Doug Ledford <dledford@redhat.com>  http://people.redhat.com/dledford
       Please check my web site for aic7xxx updates/answers before
                       e-mailing me about problems

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