Patch "dmaengine: imx-sdma: add 1ms delay to ensure SDMA channel is stopped" has been added to the 4.9-stable tree

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

dmaengine: imx-sdma: add 1ms delay to ensure SDMA channel is stopped

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-add-1ms-delay-to-ensure-sdma-channel-is-stopped.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.

From: Jiada Wang <[email protected]>
Date: Thu, 16 Mar 2017 23:12:09 -0700
Subject: dmaengine: imx-sdma: add 1ms delay to ensure SDMA channel is stopped

From: Jiada Wang <[email protected]>

[ Upstream commit 7f3ff14b7eb1ffad132117f08a1973b48e653d43 ]

sdma_disable_channel() cannot ensure dma is stopped to access module's FIFOs. There is chance 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.

According to NXP R&D team a delay of one BD SDMA cost time (maximum is 1ms) should be added after disable of the channel bit, to ensure SDMA core has really been stopped after SDMA clients call .device_terminate_all.

This patch introduces adds a new function sdma_disable_channel_with_delay() which simply adds 1ms delay after call sdma_disable_channel(), and set it as .device_terminate_all.

---
 drivers/dma/imx-sdma.c |   17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

@@ -937,6 +937,21 @@ static int sdma_disable_channel(struct d
 	return 0;
 }
 
+static int sdma_disable_channel_with_delay(struct dma_chan *chan)
+{
+	sdma_disable_channel(chan);
+
+	/*
+	 * According to NXP R&D team a delay of one BD SDMA cost time
+	 * (maximum is 1ms) should be added after disable of the channel
+	 * bit, to ensure SDMA core has really been stopped after SDMA
+	 * clients call .device_terminate_all.
+	 */
+	mdelay(1);
+
+	return 0;
+}
+
 static void sdma_set_watermarklevel_for_p2p(struct sdma_channel *sdmac)
 {
 	struct sdma_engine *sdma = sdmac->sdma;

@@ -1828,7 +1843,7 @@ static int sdma_probe(struct platform_de
 	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);

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

queue-4.9/dmaengine-imx-sdma-add-1ms-delay-to-ensure-sdma-channel-is-stopped.patch