[ivtv-users] Some video frames mangled on PVR-

Andy Walls awalls at radix.net
Wed Jan 27 03:12:46 CET 2010


On Mon, 2010-01-25 at 21:51 -0500, Andy Walls wrote:

> You are certainly welcome to look at the driver for bugs.  If trying to
> grok what the driver is doing WRT to data transfers from hardware, I
> would suggest looking at these:


> linux/drivers/media/video/ivtv/ivtv-irq.c:ivtv_irq_enc_dma_complete()

Hmm.  If the kernel's software IOMMU implementation is active on your
machine, ivtv-irq.c:dma_post() can end up performing a buffer memcpy()
in an interrupt context for buffers when calling
ivtv_buf_sync_for_cpu().

I need to fix that.  The ivtv driver should try to avoid buffer
memcpy()'s in an interrupt context for system performance reasons.


Can you check your dmesg or messages log for this:

"PCI-DMA: Using software bounce buffering for IO (SWIOTLB)"

?

Regards,
Andy




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