serial: imx.c: fix CTS trigger level lower to avoid lost chars (1c5250d6) · Commits · 戴 / test

The imx CTS trigger level is left at its reset value that is 32 chars. Since the RX FIFO has 32 entries, when CTS is raised, the FIFO already is full. However, some serial port devices first empty their TX FIFO before stopping when CTS is raised, resulting in lost chars. This patch sets the trigger level lower so that other chars arrive after CTS is raised, there is still room for 16 of them. Signed-off-by:

Valentin <Longchamp<valentin.longchamp@epfl.ch> Tested-by:

Philippe <Rétornaz<philippe.retornaz@epfl.ch> Acked-by:

Wolfram <Sang<w.sang@pengutronix.de> Cc: stable <stable@kernel.org> Signed-off-by:

Greg Kroah-Hartman <gregkh@suse.de>

drivers/serial/imx.c

+9 −1

Original line number	Diff line number	Diff line
		@@ -120,7 +120,8 @@
		#define MX2_UCR3_RXDMUXSEL (1<<2) /* RXD Muxed Input Select, on mx2/mx3 */
		#define UCR3_INVT (1<<1) /* Inverted Infrared transmission */
		#define UCR3_BPEN (1<<0) /* Preset registers enable */
		#define UCR4_CTSTL_32 (32<<10) /* CTS trigger level (32 chars) */
		#define UCR4_CTSTL_SHF 10 /* CTS trigger level shift */
		#define UCR4_CTSTL_MASK 0x3F /* CTS trigger is 6 bits wide */
		#define UCR4_INVR (1<<9) /* Inverted infrared reception */
		#define UCR4_ENIRI (1<<8) /* Serial infrared interrupt enable */
		#define UCR4_WKEN (1<<7) /* Wake interrupt enable */
		@@ -591,6 +592,9 @@ static int imx_setup_ufcr(struct imx_port *sport, unsigned int mode)
		return 0;
		}

		/* half the RX buffer size */
		#define CTSTL 16

		static int imx_startup(struct uart_port *port)
		{
		struct imx_port sport = (struct imx_port )port;
		@@ -607,6 +611,10 @@ static int imx_startup(struct uart_port *port)
		if (USE_IRDA(sport))
		temp \|= UCR4_IRSC;

		/* set the trigger level for CTS */
		temp &= ~(UCR4_CTSTL_MASK<< UCR4_CTSTL_SHF);
		temp \|= CTSTL<< UCR4_CTSTL_SHF;

		writel(temp & ~UCR4_DREN, sport->port.membase + UCR4);

		if (USE_IRDA(sport)) {

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