At Thu, 19 Jul 2007 12:59:32 -0700, Aaron "Caustik" Robinson wrote:
We have found that the problem exists because, at certain points in time, the hardware pointer and application pointer overlap. Basically the hardware is reading from the period buffer which is currently being written to. How might this be platform specific? Is there any debugging technique you think may help find the root cause?
It sounds unlikely a platform-specific problem but rather a problem of the driver implementation.
Note that the hw_ptr and appl_ptr tracked in pcm struct are within 0 and (runtime->boundary_size - 1). It's not within 0 and (buffer_size-1). So, basically it shouldn't overlap unless it goes across the boundary close to long (32bit or more).
Takashi
On 7/10/07, Jaroslav Kysela perex@suse.cz wrote:
On Tue, 10 Jul 2007, Aaron "Caustik" Robinson wrote:
This is on an embedded ARM device, with a custom driver. That's interesting. I never thought about the cache angle. Is there any sort of hack I can put to check if that is the problem?
The cache flush method is quite CPU specific, you have to check datasheet. But it's only guess and the problem might be somewhere else. I would compare samples DMA ring buffer in the user space and kernel space again. Also, put a debug lines to dmix plugin to detect where are samples written (to which pointer/area in the DMA ring buffer). dmix assumes that playback is running forever and tries to mix data in actual ring buffer position.
Jaroslav
Jaroslav Kysela perex@suse.cz Linux Kernel Sound Maintainer ALSA Project, SUSE Labs
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