[Sound-open-firmware] [PATCH 4/4] Fix DMA host offset calculation.

[Pierre-Louis Bossart]

>>> @@ -90,7 +90,7 @@ static uint64_t trace_work(void *data, uint64_t 
>>> delay)
>>>       /* update host pointer and check for wrap */
>>>       d->host_offset += size;
>>> -    if (d->host_offset + size >= d->host_size)
>>> +    if (d->host_offset >= d->host_size)
>>>           d->host_offset = 0;
>> this code pattern is present multiple times in the DMA handling code.
>> I wonder if this is correct when the > condition is true? That'd mean 
>> some overrun happened or that some bytes have been lost.
>> Shouldn't this be an exact == condition in there is a true wrap?
>
> actually we should make it to something like this for sake of safe:
>     d->host_offset -= d->host_size;
>
> but considering that we have require the host_size to be multiple of 
> period size, the '>' case won't happen, so here it is simplified to be
>     d->host_offset = 0;
>
> I agree that we should make it more robust.
Yes, my point exactly. Either the > condition happens and we have to 
handle it, or it doesn't by construction due to other restrictions and 
the test can be simplified.