'Twas brillig, and Jaroslav Kysela at 27/01/10 17:21 did gyre and gimble:
> On Wed, 27 Jan 2010, Clemens Ladisch wrote:
>
>> Jaroslav Kysela wrote:
>>> On Wed, 27 Jan 2010, Clemens Ladisch wrote:
>>>> A somewhat unrelated issue: Both old and new code assume that
>>>> hw_ptr==0 is a period boundary, but that is not true if the boundary
>>>> is not an integer multiple of the period size, and the pointer wraps.
>>>> I'm not sure what happens then.
>>>
>>> I'm not exactly sure what you're talking about. Where is the
>>> hw_ptr==0 assumption?
>>
>> This code, which tries to align hw_ptr_interrupt to a period boundary:
>>
>> runtime->hw_ptr_interrupt = new_hw_ptr -
>> (new_hw_ptr % runtime->period_size);
>
> I see. It is really problem, because if hw_ptr_interrupt shifts, then the
> condition
> delta = runtime->hw_ptr_interrupt + runtime->period_size;
> if (delta > new_hw_ptr) {
>
> is not accurate and might cause unwanted issues.
>
> The simple fix for 64-bit archs is to use "boundary = buffer_size *
> period_size" expression to setup the boundary variable properly.
>
> I added code to find the lowest common multiple for 32-bit archs.
>
> The patch is:
>
> http://git.alsa-project.org/?p=alsa-kernel.git;a=commitdiff;h=7910b4a1db63fefc3d291853d33c34c5b6352e8e
FWIW, this patch seems to have finally solved:
https://qa.mandriva.com/show_bug.cgi?id=57010
which we used to track this issue.
Had two users confirm it as fixed which is good enough for me :)
Take care and thanks.
Col
--
Colin Guthrie
gmane(at)colin.guthr.ie
http://colin.guthr.ie/
Day Job:
Tribalogic Limited [http://www.tribalogic.net/]
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