Query dw_dmac driver: All descriptors done, but channel not idle!
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From: Viresh KUMAR on 18 Jun 2010 09:40 Hello, We have Synopsys Designware DMAC Controller on ST SPEAr13xx platform. When i run dmatest for all 8 channels then i see following error some times. "dma dma0chan7: BUG: All descriptors done, but channel not idle!" I saw the code in driver, and i think it looks to be a known issue for this peripheral, that's why special handling is done in driver. Can somebody please confirm, if it a known issue or not? Or if there are some solutions for this problem. viresh. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Viresh KUMAR on 18 Jun 2010 10:00
On 6/18/2010 7:22 PM, Haavard Skinnemoen wrote: > Viresh KUMAR <viresh.kumar(a)st.com> wrote: >> Can somebody please confirm, if it a known issue or not? Or if there >> are some solutions for this problem. > > I'm not aware of any such issue. The code was added as a purely > defensive thing; when writing it, I just thought about what might > happen if we go through all our descriptors without finding the current > one, and added some code to report the issue and try to recover. > > I suppose it might be caused by some issue with the peripheral itself, > but I think it's more likely to be caused by some race condition in the > driver, i.e. something goes wrong when inserting or removing > descriptors in the chain. > > What might be very good to know at this point is the value of > the llp variable, and perhaps also the value of the CH_EN register to > see if the channel is idle or not. > Thanks Haavard, Will debug it further. viresh. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |