Re: [PATCH] sky2: receive dma mapping error handling

From: Michael Breuer
Date: Sun Jan 31 2010 - 17:03:49 EST

On 1/31/2010 1:50 PM, Michael Breuer wrote:
On 1/30/2010 11:55 PM, Michael Breuer wrote:
On 01/30/2010 07:34 PM, Jarek Poplawski wrote:

Could you try the patch below to show maybe some other users of
dma-debug entries?

Jarek P.

With the default # entries & dma_debug_driver=sky2:

6:00 is eth0 & 4:00 is eth1.

Jan 30 23:53:14 mail kernel: DMA-API: 0000:06:00.0: entries: 31961

I put a printk as a third else case in sky2_tx_unmap. Looks like the issue is that a large number (perhaps all) calls to sky2_tx_unmap have re->flags set to neither TX_MAP_SINGLE or TX_MAP_PAGE. Thus the elements are never being unmapped.

I suspect that the system collapses when using DMAR sooner than if not using DMAR. Probably some hardware limitation on the number of mapped elements that is less than the software limitation. I don't see at present how a ring element can ever get to this code without re->flags being set to one or the other.

Put some more debugging code in... re->flags is always NULL upon entry to sky2_tx_unmap.

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