[PATCH] serial imx.c: fix CTS trigger level lower to avoid lost chars
From: Wolfram Sang <hidden>
Date: 2010-01-21 22:06:53
Also in:
linux-serial
CCing linux-serial On Thu, Jan 21, 2010 at 10:26:03PM +0100, Valentin Longchamp wrote:
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.
? Isn't that a flaw of the other side? Have you spotted other serial drivers doing the same as your patch?
quoted hunk ↗ jump to hunk
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 <redacted> Tested-by: Philippe R?tornaz <redacted> --- drivers/serial/imx.c | 10 +++++++++- 1 files changed, 9 insertions(+), 1 deletions(-)diff --git a/drivers/serial/imx.c b/drivers/serial/imx.c index 18130f1..f7d2da5 100644 --- a/drivers/serial/imx.c +++ b/drivers/serial/imx.c@@ -119,7 +119,8 @@ #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 */@@ -590,6 +591,8 @@ static int imx_setup_ufcr(struct imx_port *sport, unsigned int mode) return 0; } +#define CTSTL 16 + static int imx_startup(struct uart_port *port) { struct imx_port *sport = (struct imx_port *)port;@@ -606,6 +609,11 @@ static int imx_startup(struct uart_port *port) if (USE_IRDA(sport)) temp |= UCR4_IRSC; + /* set the trigger level for CTS to 16 by default + */ + temp &= ~(UCR4_CTSTL_MASK << UCR4_CTSTL_SHF); + temp |= CTSTL << UCR4_CTSTL_SHF; + writel(temp & ~UCR4_DREN, sport->port.membase + UCR4); if (USE_IRDA(sport)) {-- 1.6.3.3 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel at lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
Regards, Wolfram -- Pengutronix e.K. | Wolfram Sang | Industrial Linux Solutions | http://www.pengutronix.de/ | -------------- next part -------------- A non-text attachment was scrubbed... Name: not available Type: application/pgp-signature Size: 197 bytes Desc: Digital signature URL: <http://lists.infradead.org/pipermail/linux-arm-kernel/attachments/20100121/c5fcc27e/attachment.sig>