From: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
To: Appana Durga Kedareswara Rao <appana.durga.rao@xilinx.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: Mon, 19 Dec 2016 19:18:54 +0200 [thread overview]
Message-ID: <2156938.MvgiZll4tB@avalon> (raw)
In-Reply-To: <C246CAC1457055469EF09E3A7AC4E11A4A65D58E@XAP-PVEXMBX01.xlnx.xilinx.com>
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.
> > Now that you catch busy channels with a software flag, do you still need
> > the xilinx_dma_is_running() and xilinx_dma_is_idle() checks ? Three
> > different checks for the same or very similar conditions are confusing,
> > if you really need them you should document clearly how they differ.
>
> Will remove the xilinx_dma_is_running and xilinx_dmais_idle() checks and
> will use Chan->idle check across all the IP's. Will fix it v2...
>
> > > @@ -1110,6 +1116,7 @@ static void xilinx_vdma_start_transfer(struct
> > > xilinx_dma_chan *chan) vdma_desc_write(chan, XILINX_DMA_REG_VSIZE,
> > > last->hw.vsize);
> > >
> > > }
> > >
> > > + chan->idle = false;
> >
> > (and this too)
>
> Will fix in v2...
--
Regards,
Laurent Pinchart
next prev parent reply other threads:[~2016-12-19 17:18 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 [this message]
2016-12-23 8:49 ` Appana Durga Kedareswara Rao
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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