There's no restriction on that the runtime->period_size should be the multiplicator of the runtime->buffer_size in current kernel code.
So "hw_ptr_interrupt = runtime->hw_ptr_interrupt + runtime->period_size;" is not always the trueth.
I've encounter the problem of this bug, the kernel told me "PCM: Unexpected hw_pointer value (stream=0, pos=8, intr_ptr=16384)".
The period_size and buffer_size I used was 0x800 and 0x3e80 when the bug occured.
Following patch will fix the bug.
Signed-off-by: Shine Liu shinel@foxmail.com -----------------------------------------------------------------------
--- a/sound/core/pcm_lib.c 2009-08-14 06:43:34.000000000 +0800 +++ b/sound/core/pcm_lib.c 2009-08-19 17:59:00.000000000 +0800 @@ -248,6 +248,12 @@ hw_base = runtime->hw_ptr_base; new_hw_ptr = hw_base + pos; hw_ptr_interrupt = runtime->hw_ptr_interrupt + runtime->period_size; + /* if the period_size is not the multiplicator of the + * buffer_size, the hw_ptr_interrupt calculated above + * may not be correct, should be fixed. + */ + if(hw_ptr_interrupt > hw_base + runtime->buffer_size) + hw_ptr_interrupt = hw_base + runtime->buffer_size; delta = new_hw_ptr - hw_ptr_interrupt; if (hw_ptr_interrupt >= runtime->boundary) { hw_ptr_interrupt -= runtime->boundary;