linux-kernel - [LINUX PATCH 2/4] dmaengine: xilinx_dma: Fix race condition in the driver for cdma

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Date:   Thu, 21 Dec 2017 15:41:36 +0530
From:   Kedareswara rao Appana <appana.durga.rao@...inx.com>
To:     <dan.j.williams@...el.com>, <vinod.koul@...el.com>,
        <michal.simek@...inx.com>, <appanad@...inx.com>, <lars@...afoo.de>,
        <akinobu.mita@...il.com>, <joabreu@...opsys.com>,
        <mike.looijmans@...ic.nl>, <kedare06@...il.com>
CC:     <dmaengine@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: [LINUX PATCH 2/4] dmaengine: xilinx_dma: Fix race condition in the driver for cdma

when hardware is idle we need to toggle the SG bit
in the control register, inorder to update new value to the
current descriptor register other wise undefined
results will occur.

This patch updates the same.

Signed-off-by: Kedareswara rao Appana <appanad@...inx.com>
---
 drivers/dma/xilinx/xilinx_dma.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/dma/xilinx/xilinx_dma.c b/drivers/dma/xilinx/xilinx_dma.c
index 21ac954..8467671 100644
--- a/drivers/dma/xilinx/xilinx_dma.c
+++ b/drivers/dma/xilinx/xilinx_dma.c
@@ -1204,6 +1204,12 @@ static void xilinx_cdma_start_transfer(struct xilinx_dma_chan *chan)
 	}
 
 	if (chan->has_sg) {
+		dma_ctrl_clr(chan, XILINX_DMA_REG_DMACR,
+			     XILINX_CDMA_CR_SGMODE);
+
+		dma_ctrl_set(chan, XILINX_DMA_REG_DMACR,
+			     XILINX_CDMA_CR_SGMODE);
+
 		xilinx_write(chan, XILINX_DMA_REG_CURDESC,
 			     head_desc->async_tx.phys);
 
@@ -2052,6 +2058,10 @@ static int xilinx_dma_terminate_all(struct dma_chan *dchan)
 		chan->cyclic = false;
 	}
 
+	if ((chan->xdev->dma_config->dmatype == XDMA_TYPE_CDMA) && chan->has_sg)
+		dma_ctrl_clr(chan, XILINX_DMA_REG_DMACR,
+			     XILINX_CDMA_CR_SGMODE);
+
 	return 0;
 }
 
-- 
2.7.4