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Date: Wed, 05 Dec 2001 16:36:31 -0500
From: Nathan Bryant <nbryant@optonline.net>
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To: Doug Ledford <dledford@redhat.com>
CC: Mario Mikocevic <mozgy@hinet.hr>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: i810 audio patch
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Doug Ledford wrote:

> This didn't used to be a bug, but it is now (all these changes and 
> merges have let some thigns slip in I'm afraid, and I'm not just 
> referring to the work in the last few days, I'm also referring to 
> changes that were lost in the time of the S/PDIF and PM merges). 

Agreed. There are some uglies...

>
>
> Anyway, in i810_write, the lines that read:
>
> if (cnt > (dmabuf->dmasize - dmabuf->count))
>     cnt = dmabuf->dmasize - dmabuf->count;
>
> should read:
>
> if (cnt > (dmabuf->dmasize - swptr))
>     cnt = dmabuf->dmasize - swptr; 

Okay. I thought I was being stupid. :-)

> 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? 

Actually, I think I *may* have found the problem, in update ptr, it 
should look like this: going to test in a moment

        /* error handling and process wake up for DAC */
        if (dmabuf->enable == DAC_RUNNING) {
                /* update hardware pointer */
                hwptr = i810_get_dma_addr(state, 0);
                diff = hwptr - dmabuf->hwptr;
                if (hwptr < dmabuf->hwptr)
                        diff += dmabuf->dmasize;
#if defined(DEBUG_INTERRUPTS) || defined(DEBUG_MMAP)
                printk("DAC HWP %d,%d,%d\n", hwptr, dmabuf->hwptr, diff);
#endif

reason: hwptr hits 65536 which is indistinguishable from 0 in mod arithmetic

also, I ran your other DEBUG_MMAP patch and the news is that count just 
sits at 65536 ad nauseum.

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