2015-6-22 下午2:43 於 "Lars-Peter Clausen" lars@metafoo.de 寫道：
On 06/22/2015 04:35 AM, Raymond Yau wrote:
DMA_RESIDUE_GRANULARITY_BURST means it can report the position with a
granularity of a few samples. Typically half the audio FIFO size.
How many soc driver/platform dma engine support
DMA_RESIDUE_GRANULARITY_BURST ?
Not sure, maybe half of them. But most of the time it is a software
restriction rather than a hardware restriction and more and more drivers are supporting it.
https://bugs.freedesktop.org/attachment.cgi?id=107650
snd_rpi_hifiberry_amp
granularity seem 4 frames most of the time but sometime there is a large delay between 3584 and 3988 ,seem cannot reach 4096
Available: 3580, loop iteration: 420 Available: 3584, loop iteration: 421 Available: 3988, loop iteration: 422 Available: 3996, loop iteration: 423 Available: 4004, loop iteration: 424 Available: 4012, loop iteration: 425
Are the pointer callback really use value read from hardware register or value calculated from clock ?