6.9-stable review patch. If anyone has any objections, please let me know.
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From: Matthias Schiffer matthias.schiffer@ew.tq-group.com
[ Upstream commit a3d8728ab079951741efa11360df43dbfacba7ab ]
At the default TX trigger level of 2 in non-DMA mode (meaning that an interrupt is generated when less than 2 characters are left in the FIFO), we have observed frequent buffer underruns at 115200 Baud on an i.MX8M Nano. This can cause communication issues if the receiving side expects a continuous transfer.
Increasing the level to 8 makes the UART trigger an interrupt earlier, giving the kernel enough time to refill the FIFO, at the cost of triggering one interrupt per ~24 instead of ~30 bytes of transmitted data (as the i.MX UART has a 32 byte FIFO).
Signed-off-by: Michael Krummsdorf michael.krummsdorf@tq-group.com Signed-off-by: Matthias Schiffer matthias.schiffer@ew.tq-group.com Link: https://lore.kernel.org/r/20240508133744.35858-1-matthias.schiffer@ew.tq-gro... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/tty/serial/imx.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c index 9552228d21614..f63cdd6794419 100644 --- a/drivers/tty/serial/imx.c +++ b/drivers/tty/serial/imx.c @@ -1314,7 +1314,7 @@ static void imx_uart_clear_rx_errors(struct imx_port *sport)
}
-#define TXTL_DEFAULT 2 /* reset default */ +#define TXTL_DEFAULT 8 #define RXTL_DEFAULT 8 /* 8 characters or aging timer */ #define TXTL_DMA 8 /* DMA burst setting */ #define RXTL_DMA 9 /* DMA burst setting */