Messages in this thread | | | Date | Sat, 04 Jul 2009 00:12:45 +0900 (JST) | Subject | Re: [PATCH 1/2 v2] dmaengine: at_hdmac: new driver for the Atmel AHB DMA Controller | From | Atsushi Nemoto <> |
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On Wed, 01 Jul 2009 17:30:54 +0200, Nicolas Ferre <nicolas.ferre@atmel.com> wrote: > > Some of issues reported at that time could be applied on your driver > > too. With a quick look, the queue list management issue is a > > candidate. Here is an excerpt from the thread: .... > > I try to replay the life of a descriptor chain in "queue" list: > - it is queued by atc_tx_submit() > - tasklet or atc_issue_pendig() will "advance_work" and so run > atc_complete_all() at some point. > - atc_complete_all() will issue an atc_dostart() on the first chain in > queue list and move all to active_list > - then all chains will be managed as active_list members: > - tasklet or atc_issue_pendig() will "advance_work" > - first member will be managed by chain_complete() > - next member will be started by dostart() > - and so on... > - last chain in active_list will run complete_all() and may move again > queued descriptors to active_list. > > => non-first descriptor moved from queue to active_list will be > proceeded by act_dostart() in atc_advance_work() function.
Oh yes. I was wrong. I missed act_dostart() in atc_advance_work(). Sorry for false warning.
> In this way of addressing descriptors, I try to keep descriptor chains > as they are built by the prep_dma_memcpy function. I am not trying to > rewrite the internal arrangement of a descriptor chain (not touching > lli.dscr). > It may be not optimal for the descriptor management speed but it tries > to split problems in a kind of layered way (we build chains and then > manage their flow in dma engine and associated lists). > > I hope that there is no hole in this management as I am sure it is > difficult to debug... > I hope that my response is solid enough. Please do not hesitate to break > my demonstration ;-).
Thank you for elaboration, I cannot find any hole now. Indeed these kind of problem is hard to debug. Running dmatest with threads_per_chan=N will catch such issues, hopefully :-)
--- Atsushi Nemoto
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