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Date: Wed, 05 Dec 2001 22:39:17 -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:

> as evidenced by,
> 
> 
>        /* if we are currently stopped, then our CIV is actually set to our
>         * *last* sg segment and we are ready to wrap to the next.  However,
>         * if we set our LVI to the last sg segment, then it won't wrap to
>         * the next sg segment, it won't even get a start.  So, instead, 
> when
>         * we are stopped, we set both the LVI value and also we increment
>         * the CIV value to the next sg segment to be played so that when
>         * we call start_{dac,adc}, things will operate properly
>         */
>        if (!dmabuf->enable) {
> #ifdef DEBUG_MMAP
>                printk("fnord? %d\n", inb(port+OFF_CIV));
> #endif
>                /* maybe we have to increment LVI to make room before 
> incrementing CIV,
>                   (databook says CELV isn't cleared until new val written
>                    to LVI.)
>                   we'll set LVI where we really want it down below. */
>                //outb((inb(port+OFF_LVI)+1)&31, port+OFF_LVI);
>                newciv = (inb(port+OFF_CIV)+1)&31;
>                outb(newciv, port+OFF_CIV);
>                for (x = 0; inb(port+OFF_CIV) != newciv && x< 5000000; x++);
>                if (x==5000000) printk("foo! civ != %d\n", newciv);
>        }
> 
> and
> 
> Dec  5 21:34:32 lasn-001 kernel: foo! civ != 1
> 
> CIV doesn't seem to respond to writes on my chipset, at least not in 
> this situation. you'll note that nowhere in the driver are we 
> initializing CIV to anything other than 0 anyway.
> 
> two alternatives I can think of:
> 
> first fix:
> set LVI to desired value minus one SG
> start_dac (which should have side effect of incrementing CIV by one)
> increment LVI to desired value
> 
> 2nd fix:
> back off and perform DMA reset.
> 
> 3rd fix (really fix 1a ;)
> just don't allow use of the last SG when restarting
> 

Try this out:
         /* if we are currently stopped, then our CIV is actually set to our
          * *last* sg segment and we are ready to wrap to the next. 
However,
          * if we set our LVI to the last sg segment, then it won't wrap to
          * the next sg segment, it won't even get a start.  So, 
instead, when
          * we are stopped, we set both the LVI value and also we increment
          * the CIV value to the next sg segment to be played so that when
          * we call start_{dac,adc}, things will operate properly
          */
         if (!dmabuf->enable) {
                 outb((inb(port+OFF_CIV)+1)&31, port+OFF_LVI);
                 if(rec) {
                         __start_adc(state);
                         while( !(inb(port + OFF_CR) & ((1<<4) | (1<<2))) )
                                 barrier();
                 } else {
                         __start_dac(state);
                         while( !(inb(port + OFF_CR) & ((1<<4) | (1<<2))) )
                                 barrier();
                 }
         }



-- 

  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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