Thread (16 messages) 16 messages, 3 authors, 2016-12-23

[PATCH 1/3] dmaengine: xilinx_dma: Check for channel idle state before submitting dma descriptor

From: appana.durga.rao@xilinx.com (Appana Durga Kedareswara Rao)
Date: 2016-12-19 15:54:05
Also in: lkml

Hi Laurent Pinchart,

	Thanks for the review...
quoted
+	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.
quoted
 	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.
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...
quoted
@@ -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,
Kedar.
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