MLK-13794: BACKPORT: dmaengine: imx-sdma - correct the dma transfer residue calculation

This patch fixes crackling sound reported when running autorun-asrc.sh
and it is a backport of 85f57752b3 ("dmaengine: imx-sdma - correct
the dma transfer residue calculation") from v10-rc6.

Original commit message:

	From: Nandor Han <nandor.han@ge.com>
	Date: Tue, 11 Oct 2016 14:13:41 +0300
	Subject: [PATCH] dmaengine: imx-sdma - correct the dma transfer residue
	 calculation

	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@ge.com>
Acked-by: Peter Senna Tschudin <peter.senna@collabora.com>
Tested-by: Peter Senna Tschudin <peter.senna@collabora.com>
Tested-by: Marek Vasut <marex@denx.de>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Daniel Baluta <daniel.baluta@nxp.com>

diff --git a/drivers/dma/imx-sdma.c b/drivers/dma/imx-sdma.c
index 581df66..5fbe320 100644 (file)
--- a/drivers/dma/imx-sdma.c
+++ b/drivers/dma/imx-sdma.c
@@ -1312,6 +1312,8 @@ static int sdma_transfer_init(struct sdma_channel *sdmac,
 
        sdmac->status = DMA_IN_PROGRESS;
        sdmac->buf_tail = 0;
+       sdmac->buf_ptail = 0;
+       sdmac->chn_real_count = 0;
        sdmac->flags = 0;
        sdmac->direction = direction;
        sdmac->flags = 0;