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authorKoen Vandeputte <koen.vandeputte@ncentric.com>2018-02-22 12:20:16 +0100
committerFelix Fietkau <nbd@nbd.name>2018-02-22 12:46:49 +0100
commitefb362cd93b0c3d308685a37417fb62991878f4c (patch)
tree02e4fbe0a9ccbd63f1e0356fef7a5506dfad578c /target/linux
parentaad1f11efe1c0f761d3454ac371fd98e65284b35 (diff)
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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. Boot log: [ 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@ncentric.com>
Diffstat (limited to 'target/linux')
-rw-r--r--target/linux/imx6/patches-4.14/210-disable-uart-dma.patch23
1 files changed, 23 insertions, 0 deletions
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
index 0000000000..6abbb93301
--- /dev/null
+++ b/target/linux/imx6/patches-4.14/210-disable-uart-dma.patch
@@ -0,0 +1,23 @@
+Based on following upstream patch by Tim Harvey (Gateworks):
+
+https://github.com/Gateworks/openwrt/commit/80a01b6582f94c4547f39d3a25e0a1e9b6eb9877
+
+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.
+
+--- a/drivers/tty/serial/imx.c
++++ b/drivers/tty/serial/imx.c
+@@ -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)
+- imx_uart_dma_init(sport);
+-
+ spin_lock_irqsave(&sport->port.lock, flags);
+ /* Reset fifo's and state machines */
+ i = 100;