6.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Matthias Schiffer <matthias.schiffer@xxxxxxxxxxxxxxx> [ 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@xxxxxxxxxxxx> Signed-off-by: Matthias Schiffer <matthias.schiffer@xxxxxxxxxxxxxxx> Link: https://lore.kernel.org/r/20240508133744.35858-1-matthias.schiffer@xxxxxxxxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- 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 */ -- 2.43.0
