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authorValentin Longchamp <valentin.longchamp@epfl.ch>2010-05-05 11:47:07 +0200
committerGreg Kroah-Hartman <gregkh@suse.de>2010-05-26 14:29:16 -0700
commit5eb1c77df310f6def7a8d9e9e2e2061142a2ad63 (patch)
tree17827f47d789783ed79cd094ee8888bbe351e03d
parentcfbca0d1ae392a3b4fb490094ddb951d96591ef3 (diff)
serial: imx.c: fix CTS trigger level lower to avoid lost chars
commit 1c5250d6163dac28be3afabdfb6c723f107051b7 upstream. 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 R├ętornaz<philippe.retornaz@epfl.ch> Acked-by: Wolfram Sang<w.sang@pengutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
-rw-r--r--drivers/serial/imx.c10
1 files changed, 9 insertions, 1 deletions
diff --git a/drivers/serial/imx.c b/drivers/serial/imx.c
index 8c0dd1361d30..2b550182a879 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 +591,9 @@ 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;
@@ -606,6 +610,10 @@ 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)) {