From: wangx@marvell•com (Xiang Wang)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH v4 1/4] dma: mmp_pdma: only complete one transaction from dma_do_tasklet()
Date: Tue, 20 Aug 2013 10:27:37 +0800 [thread overview]
Message-ID: <5212D419.5030504@marvell.com> (raw)
In-Reply-To: <1376672707-24527-2-git-send-email-zonque@gmail.com>
On 08/17/2013 01:05 AM, Daniel Mack wrote:
> Currently, when an interrupt has occured for a channel, the tasklet
> worker code will only look at the very last entry in the running list
> and complete its cookie, and then dispose the entire running chain.
> Hence, the first transaction's cookie will never complete.
>
> In fact, the interrupt we should handle will be the one related to the
> first descriptor in the chain with the ENDIRQEN bit set, so complete
> the second transaction that is in fact still running.
>
> As a result, the driver can't currently handle multiple transactions on
> one chanel, and it's likely that no drivers exist that rely on this
> feature.
>
> Fix this by walking the running_chain and look for the first
> descriptor that has the interrupt-enable bit set. Only queue
> descriptors up to that point for completion handling, while leaving
> the rest intact. Also, only make the channel idle if the list is
> completely empty after such a cycle.
>
> Signed-off-by: Daniel Mack <zonque@gmail•com>
> ---
> drivers/dma/mmp_pdma.c | 35 +++++++++++++++++++++--------------
> 1 file changed, 21 insertions(+), 14 deletions(-)
>
Hi, Daniel
I think we would not run into the situation that there is a descriptor
with ENDIRQEN set in the middle of the running chain.
in mmp_pdma.c:
mmp_pdma_tx_submit() -> append_pending_queue() ->
tail->desc.dcmd &= ~DCMD_ENDIRQEN;
So in the pending list (same for running list), only the last descriptor
will have ENDIRQEN set.
Please correct me if any problems.
--
Regards,
Xiang
next prev parent reply other threads:[~2013-08-20 2:27 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-08-16 17:05 [PATCH v4 0/4] dma: pdma: cyclic, residue, DMA_PRIVATE Daniel Mack
2013-08-16 17:05 ` [PATCH v4 1/4] dma: mmp_pdma: only complete one transaction from dma_do_tasklet() Daniel Mack
2013-08-20 2:27 ` Xiang Wang [this message]
2013-08-20 7:44 ` Daniel Mack
2013-08-25 1:15 ` Robert Jarzmik
2013-08-16 17:05 ` [PATCH v4 2/4] dma: mmp_pdma: add support for cyclic DMA descriptors Daniel Mack
2013-08-16 17:05 ` [PATCH v4 3/4] dma: mmp_pdma: add support for residue reporting Daniel Mack
2013-08-21 11:35 ` Xiang Wang
2013-08-21 11:52 ` Andy Shevchenko
2013-08-21 12:03 ` Daniel Mack
2013-08-21 12:08 ` Andy Shevchenko
2013-08-25 16:11 ` Vinod Koul
2013-08-25 17:01 ` Russell King - ARM Linux
2013-08-25 16:48 ` Vinod Koul
2013-08-25 18:06 ` Russell King - ARM Linux
2013-08-26 6:07 ` Robert Jarzmik
2013-08-21 11:55 ` Daniel Mack
2013-08-16 17:05 ` [PATCH v4 4/4] dma: mmp_pdma: set DMA_PRIVATE Daniel Mack
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