Messages in this thread | | | Date | Sat, 05 Feb 2011 09:41:44 -0800 | From | Dan Williams <> | Subject | Re: DMA |
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On 02/04/2011 01:01 PM, mahdi hamzeh wrote: > Paul, > > Thanks for your help. You were right. There was a version mismatch > between my header files and I got it fixed. I could compile all > related dma modules including async modules. However, I cannot use dma > engine because I receive following error when I run my code, > "__dma_request_channel: fail ((null))". Even I tried > Documentation/crypto/async-tx-api.txt but it turns out that when I > issue a transaction such that "async_memcpy" and I wait for > transaction to be completed by "wait_for_completion", it is never > completed. Is this problem related to my machine or my code? > > Here is my code: > > struct async_submit_ctl submit; > struct completion cmp; > init_completion(&cmp); > init_async_submit(&submit, flag, NULL, NULL,&cmp, addr_conv); ^^^^ Hmm... what's wrong with this parameter? ;-)
> dma_cap_mask_t myMask; > dma_cap_zero(myMask); > dma_cap_set(DMA_PRIVATE, myMask); //I tried different combination of > flags like DMA_MEMCPY ,.... > myDMAChannel = dma_request_channel(myMask, NULL, filter_param); > > myDMAChannel is always NULL.
This is a bit more subtle. Depending on the driver and the kernel configuration all channels may already be consumed for "public" usage (NET_DMA and/or ASYNC_TX_DMA).
One way to sanity check your system is to turn off CONFIG_NET_DMA and CONFIG_ASYNC_TX_DMA and turn on CONFIG_DMATEST, load dmatest.ko and it should give a clue about whether dma is operational on your platform.
-- Dan
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