[openwrt/openwrt] imx6: disable dma on uart
lede-commits at lists.infradead.org
Thu Feb 22 03:47:26 PST 2018
nbd pushed a commit to openwrt/openwrt.git, branch master:
Author: Koen Vandeputte <koen.vandeputte at ncentric.com>
AuthorDate: Thu Feb 22 12:20:16 2018 +0100
imx6: disable dma on uart
When this target got updated to 4.14, this patch got removed to
re-evaluate if it was still needed.
Extensive testing now shows this issue is still present.
Let's re-add the patch to fix it for now.
As the uart bus is very low bandwidth .. performance impact is negligible.
[ 22.513051] imx-uart 2020000.serial: DMA transaction error.
[ 22.522721] imx-uart 2020000.serial: DMA transaction error.
As a sidenote:
The patch mentiones an issue with RS485, but the bootlog
errors above were recorded with the uart ports in standard RS232 mode.
Compile/Run-tested on imx6/GW5200
Signed-off-by: Koen Vandeputte <koen.vandeputte at ncentric.com>
.../imx6/patches-4.14/210-disable-uart-dma.patch | 23 ++++++++++++++++++++++
1 file changed, 23 insertions(+)
diff --git a/target/linux/imx6/patches-4.14/210-disable-uart-dma.patch b/target/linux/imx6/patches-4.14/210-disable-uart-dma.patch
new file mode 100644
@@ -0,0 +1,23 @@
+Based on following upstream patch by Tim Harvey (Gateworks):
+TX complete DMA messages are getting missed.
+This is also currently an issue in mainline.
+For now we will disable DMA in serial/imx.c.
+This resolves an issue encountered with RS485 transmit.
+@@ -1268,10 +1268,6 @@ static int imx_startup(struct uart_port
+ writel(temp & ~UCR4_DREN, sport->port.membase + UCR4);
+- /* Can we enable the DMA support? */
+- if (!uart_console(port) && !sport->dma_is_inited)
+ spin_lock_irqsave(&sport->port.lock, flags);
+ /* Reset fifo's and state machines */
+ i = 100;
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