On 07/12/11 20:54, Javi Merino wrote: > On 07/12/11 10:01, Javi Merino wrote: >> On 07/12/11 07:52, Kukjin Kim wrote: >>> Jassi Brar wrote: >>>> On 29 November 2011 15:23, Javi Merino <javi.merino@xxxxxxx> wrote: >>>>>>>>>> On Samsung's Exynos4 platform, while testing audio playback with >>>>>>> i2s >>>>>>>>>> interface, the above change causes the playback to freeze. The >>>>>>>>>> _thrd_active(thrd) call always returns '1' and hence _start(thrd) >>>>>>> is >>>>>>>>>> not getting called. >>>>>>>>> >>>>>>>> Your patch makes the memcpy operation on dmatest.c and net DMA be >>>>>>> frozen too >>>>>>>> as well as Samsung audio playback. >>>>>>> >>>> Javi, could you please check if you too get the memcpy failure with >>>> dmatest ? >>> > Ok, I think I've just reproduced it in my end with the kernel's dmatest > module. After the first transaction it looks like the dma test wasn't > able to issue any more transactions. I'll have a look at it tomorrow > and try to answer my own questions ;) The problem is that pl330_submit_req() always puts the request in buffer 0 if both buffers are free. If you submit a transaction, it finishes and there's nothing else to run, pl330_update() calls _start() but there is nothing to send. This is all right. Then, if another transaction is submitted, pl330_submit_req() will put it in buffer 0 again. This time, the PC of the DMA is in the last instruction of buffer 0 (the DMAEND of the *previous* transaction that finished long ago) so _thrd_active() thinks that this buffer is active, which makes pl330_chan_ctrl() not start the transaction and hence, the DMA freezes. I believe something like the following should fix it: --- a/arch/arm/common/pl330.c +++ b/arch/arm/common/pl330.c @@ -1301,7 +1301,7 @@ int pl330_submit_req(void *ch_id, struct pl330_req *r) goto xfer_exit; } - idx = IS_FREE(&thrd->req[0]) ? 0 : 1; + idx = IS_FREE(&thrd->req[1 - thrd->lstenq]) ? 1 - thrd->lstenq : thrd->lstenq; xs.ccr = ccr; xs.r = r; I have only tested this with a single-channel single-thread dma test. I'll send a proper patch to the list once I've done more testing. Cheers, Javi -- To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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