From: Appana Durga Kedareswara Rao <appana.durga.rao@xilinx.com>
To: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: "dan.j.williams@intel.com" <dan.j.williams@intel.com>,
"vinod.koul@intel.com" <vinod.koul@intel.com>,
"michal.simek@xilinx.com" <michal.simek@xilinx.com>,
Soren Brinkmann <sorenb@xilinx.com>,
"moritz.fischer@ettus.com" <moritz.fischer@ettus.com>,
"luis@debethencourt.com" <luis@debethencourt.com>,
"Jose.Abreu@synopsys.com" <Jose.Abreu@synopsys.com>,
"dmaengine@vger.kernel.org" <dmaengine@vger.kernel.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH 1/3] dmaengine: xilinx_dma: Check for channel idle state before submitting dma descriptor
Date: Fri, 23 Dec 2016 08:49:07 +0000 [thread overview]
Message-ID: <C246CAC1457055469EF09E3A7AC4E11A4A65F569@XAP-PVEXMBX01.xlnx.xilinx.com> (raw)
In-Reply-To: <2156938.MvgiZll4tB@avalon>
Hi Laurent Pinchart,
Sorry for the delay in the reply.
Thanks for the review...
>
> Hi Kedar,
>
> On Monday 19 Dec 2016 15:39:43 Appana Durga Kedareswara Rao wrote:
> > Hi Laurent Pinchart,
> >
> > Thanks for the review...
> >
> > > > + if (!chan->idle)
> > > > + return;
> > >
> > > Don't you need to perform the same check for the DMA and CDMA channels
> ?
> > > If so, shouldn't this be moved to common code ?
> >
> > Will fix it in v2...
> >
> > > There's another problem (not strictly introduced by this patch) I
> > > wanted to mention. The append_desc_queue() function, called from
> > > your tx_submit handler, appends descriptors to the pending_list. The
> > > DMA engine API states that a transfer submitted by tx_submit will
> > > not be executed until
> > > .issue_pending() is called. However, if a transfer is in progress at
> > > tx_submit time, I believe that the IRQ handler, at transfer
> > > completion, will start the next transfer from the pending_list even
> > > if
> > > .issue_pending() hasn't been called for it.
> > >
> > > > if (list_empty(&chan->pending_list))
> > > > return;
> >
> > If user submits more than h/w limit then that case only driver will
> > process The descriptors from the pending_list for other cases the
> > pending_list will be Empty so driver just returns from there.
>
> I understand that, but that's not the problem. Your .tx_submit() handler calls
> append_desc_queue() which adds the tx descriptor to the pending_list. If a
> transfer is in progress at that time, I believe the transfer completion IRQ handler
> will take the next descriptor from the pending_list and process it, even though
> issue_pending() hasn't been called for it.
>
Thanks for the explanation...
Agree will keep this my to-do list...
Regards,
Kedar.
next prev parent reply other threads:[~2016-12-23 9:21 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-15 15:11 [PATCH 0/3] dmaengine: xilinx_dma: Bug fixes Kedareswara rao Appana
2016-12-15 15:11 ` [PATCH 1/3] dmaengine: xilinx_dma: Check for channel idle state before submitting dma descriptor Kedareswara rao Appana
2016-12-15 15:45 ` Jose Abreu
2016-12-15 18:49 ` Appana Durga Kedareswara Rao
2016-12-16 15:35 ` Laurent Pinchart
2016-12-19 15:39 ` Appana Durga Kedareswara Rao
2016-12-19 17:18 ` Laurent Pinchart
2016-12-23 8:49 ` Appana Durga Kedareswara Rao [this message]
2016-12-15 15:11 ` [PATCH 2/3] dmaeninge: xilinx_dma: Fix bug in multiple frame stores scenario in vdma Kedareswara rao Appana
2016-12-15 16:10 ` Jose Abreu
2016-12-15 19:09 ` Appana Durga Kedareswara Rao
2016-12-16 10:11 ` Jose Abreu
2016-12-19 15:40 ` Appana Durga Kedareswara Rao
2016-12-16 15:54 ` Laurent Pinchart
2016-12-19 15:41 ` Appana Durga Kedareswara Rao
2016-12-15 15:11 ` [PATCH 3/3] dmaengine: xilinx_dma: Fix race condition in the driver for multiple descriptor scenario Kedareswara rao Appana
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