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Patch "dmaengine: imx-sdma - correct the dma transfer residue calculation" has been added to the 4.9-stable tree

PATCH [email protected] 1 participant 1 message Mar 12, 2017

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This is a note to let you know that I've just added the patch titled

dmaengine: imx-sdma - correct the dma transfer residue calculation

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
dmaengine-imx-sdma-correct-the-dma-transfer-residue-calculation.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

Quoted 1 line

From 85f57752b33cf12f1d583f0c10b752292de00abe Mon Sep 17 00:00:00 2001

From: Nandor Han <[email protected]>
Date: Tue, 11 Oct 2016 14:13:41 +0300
Subject: dmaengine: imx-sdma - correct the dma transfer residue calculation

From: Nandor Han <[email protected]>

commit 85f57752b33cf12f1d583f0c10b752292de00abe upstream.

The residue calculation was taking in consideration that dma transaction status will be always retrieved in the dma callback used to inform that dma transfer is complete. However this is not the case for all subsystems that use dma. Some subsystems use a timer to check the dma status periodically.

Therefore the calculation was updated and residue is calculated accordingly by a) update the residue calculation taking in consideration the last used buffer index by using *buf_ptail* variable and b) chn_real_count (number of bytes transferred) is initialized to zero, when dma channel is created, to avoid using an uninitialized value in residue calculation when dma status is checked without waiting dma complete event.

Signed-off-by Nandor Han <[email protected]>
Acked-by Peter Senna Tschudin <[email protected]>
Tested-by Peter Senna Tschudin <[email protected]>
Tested-by Marek Vasut <[email protected]>
Signed-off-by Vinod Koul <[email protected]>
Cc Fabio Estevam <[email protected]>
Signed-off-by Greg Kroah-Hartman <[email protected]>
---
 drivers/dma/imx-sdma.c |   13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)
drivers/dma/imx-sdma.c +9 -4
@@ -298,6 +298,7 @@ struct sdma_engine;
  * @event_id1		for channels that use 2 events
  * @word_size		peripheral access size
  * @buf_tail		ID of the buffer that was processed
+ * @buf_ptail		ID of the previous buffer that was processed
  * @num_bd		max NUM_BD. number of descriptors currently handling
  */
 struct sdma_channel {

@@ -309,6 +310,7 @@ struct sdma_channel {
 	unsigned int			event_id1;
 	enum dma_slave_buswidth		word_size;
 	unsigned int			buf_tail;
+	unsigned int			buf_ptail;
 	unsigned int			num_bd;
 	unsigned int			period_len;
 	struct sdma_buffer_descriptor	*bd;

@@ -700,6 +702,8 @@ static void sdma_update_channel_loop(str
 		sdmac->chn_real_count = bd->mode.count;
 		bd->mode.status |= BD_DONE;
 		bd->mode.count = sdmac->period_len;
+		sdmac->buf_ptail = sdmac->buf_tail;
+		sdmac->buf_tail = (sdmac->buf_tail + 1) % sdmac->num_bd;
 
 		/*
 		 * The callback is called from the interrupt context in order

@@ -710,9 +714,6 @@ static void sdma_update_channel_loop(str
 
 		dmaengine_desc_get_callback_invoke(&sdmac->desc, NULL);
 
-		sdmac->buf_tail++;
-		sdmac->buf_tail %= sdmac->num_bd;
-
 		if (error)
 			sdmac->status = old_status;
 	}

@@ -1186,6 +1187,8 @@ static struct dma_async_tx_descriptor *s
 	sdmac->flags = 0;
 
 	sdmac->buf_tail = 0;
+	sdmac->buf_ptail = 0;
+	sdmac->chn_real_count = 0;
 
 	dev_dbg(sdma->dev, "setting up %d entries for channel %d.\n",
 			sg_len, channel);

@@ -1288,6 +1291,8 @@ static struct dma_async_tx_descriptor *s
 	sdmac->status = DMA_IN_PROGRESS;
 
 	sdmac->buf_tail = 0;
+	sdmac->buf_ptail = 0;
+	sdmac->chn_real_count = 0;
 	sdmac->period_len = period_len;
 
 	sdmac->flags |= IMX_DMA_SG_LOOP;

@@ -1385,7 +1390,7 @@ static enum dma_status sdma_tx_status(st
 	u32 residue;
 
 	if (sdmac->flags & IMX_DMA_SG_LOOP)
-		residue = (sdmac->num_bd - sdmac->buf_tail) *
+		residue = (sdmac->num_bd - sdmac->buf_ptail) *
 			   sdmac->period_len - sdmac->chn_real_count;
 	else
 		residue = sdmac->chn_count - sdmac->chn_real_count;

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/dmaengine-imx-sdma-correct-the-dma-transfer-residue-calculation.patch