linux-kernel - [PATCH 1/1] dma: imx-sdma: add 1ms delay to ensure SDMA channel is stopped

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Message-ID: <1486738005-4297-1-git-send-email-jiada_wang@mentor.com>
Date:   Fri, 10 Feb 2017 06:46:45 -0800
From:   <jiada_wang@...tor.com>
To:     <dan.j.williams@...el.com>, <vinod.koul@...el.com>
CC:     <dmaengine@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <jiada_wang@...tor.com>
Subject: [PATCH 1/1] dma: imx-sdma: add 1ms delay to ensure SDMA channel is stopped

From: Jiada Wang <jiada_wang@...tor.com>

sdma_disable_channel() cannot ensure dma is stopped to access
module's FIFOs. Maybe SDMA core is running and accessing BD when
disable of corresponding channel, this may cause sometimes even
after call of .sdma_disable_channel(), SDMA core still be running
and accessing module's FIFOs.

We should add delay of one BD SDMA cost time, the maximum is 1ms.
So that SDMA clients by calling .device_terminate_all can
ensure SDMA core has really been stopped.

Signed-off-by: Jiada Wang <jiada_wang@...tor.com>
---
 drivers/dma/imx-sdma.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/dma/imx-sdma.c b/drivers/dma/imx-sdma.c
index d1651a5..7332c40 100644
--- a/drivers/dma/imx-sdma.c
+++ b/drivers/dma/imx-sdma.c
@@ -937,6 +937,14 @@ static int sdma_disable_channel(struct dma_chan *chan)
 	return 0;
 }
 
+static int sdma_disable_channel_with_delay(struct dma_chan *chan)
+{
+	sdma_disable_channel(chan);
+	mdelay(1);
+
+	return 0;
+}
+
 static void sdma_set_watermarklevel_for_p2p(struct sdma_channel *sdmac)
 {
 	struct sdma_engine *sdma = sdmac->sdma;
@@ -1828,7 +1836,7 @@ static int sdma_probe(struct platform_device *pdev)
 	sdma->dma_device.device_prep_slave_sg = sdma_prep_slave_sg;
 	sdma->dma_device.device_prep_dma_cyclic = sdma_prep_dma_cyclic;
 	sdma->dma_device.device_config = sdma_config;
-	sdma->dma_device.device_terminate_all = sdma_disable_channel;
+	sdma->dma_device.device_terminate_all = sdma_disable_channel_with_delay;
 	sdma->dma_device.src_addr_widths = BIT(DMA_SLAVE_BUSWIDTH_4_BYTES);
 	sdma->dma_device.dst_addr_widths = BIT(DMA_SLAVE_BUSWIDTH_4_BYTES);
 	sdma->dma_device.directions = BIT(DMA_DEV_TO_MEM) | BIT(DMA_MEM_TO_DEV);
-- 
2.7.4