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 <stable@xxxxxxxxxxxxxxx> know about it.
>From 85f57752b33cf12f1d583f0c10b752292de00abe Mon Sep 17 00:00:00 2001
From: Nandor Han <nandor.han@xxxxxx>
Date: Tue, 11 Oct 2016 14:13:41 +0300
Subject: dmaengine: imx-sdma - correct the dma transfer residue calculation
From: Nandor Han <nandor.han@xxxxxx>
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 <nandor.han@xxxxxx>
Acked-by: Peter Senna Tschudin <peter.senna@xxxxxxxxxxxxx>
Tested-by: Peter Senna Tschudin <peter.senna@xxxxxxxxxxxxx>
Tested-by: Marek Vasut <marex@xxxxxxx>
Signed-off-by: Vinod Koul <vinod.koul@xxxxxxxxx>
Cc: Fabio Estevam <festevam@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/dma/imx-sdma.c | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)
--- a/drivers/dma/imx-sdma.c
+++ b/drivers/dma/imx-sdma.c
@@ -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 nandor.han@xxxxxx are
queue-4.9/dmaengine-imx-sdma-correct-the-dma-transfer-residue-calculation.patch