From c4415084218c68c5ee2fc583431e89a78d896b19 Mon Sep 17 00:00:00 2001 From: Dmitry Fink Date: Mon, 8 Jul 2013 13:04:44 +0300 Subject: [PATCH] OMAP: UART: Keep the TX fifo full when possible Current logic results in interrupt storm since the fifo is constantly below the threshold level. Change the logic to fill all the available spaces in the fifo as long as we have data to minimize the possibilty of underflow and elimiate excessive interrupts. Signed-off-by: Dmitry Fink Signed-off-by: Alexander Savchenko Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/omap-serial.c | 3 ++- include/uapi/linux/serial_reg.h | 1 + 2 files changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/tty/serial/omap-serial.c b/drivers/tty/serial/omap-serial.c index 33c758e..9271a1d 100644 --- a/drivers/tty/serial/omap-serial.c +++ b/drivers/tty/serial/omap-serial.c @@ -315,7 +315,8 @@ static void transmit_chars(struct uart_omap_port *up, unsigned int lsr) serial_omap_stop_tx(&up->port); return; } - count = up->port.fifosize / 4; + count = up->port.fifosize - + (serial_in(up, UART_OMAP_TXFIFO_LVL) & 0xFF); do { serial_out(up, UART_TX, xmit->buf[xmit->tail]); xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1); diff --git a/include/uapi/linux/serial_reg.h b/include/uapi/linux/serial_reg.h index e632260..97c26be 100644 --- a/include/uapi/linux/serial_reg.h +++ b/include/uapi/linux/serial_reg.h @@ -366,6 +366,7 @@ #define UART_OMAP_MDR1_FIR_MODE 0x05 /* FIR mode */ #define UART_OMAP_MDR1_CIR_MODE 0x06 /* CIR mode */ #define UART_OMAP_MDR1_DISABLE 0x07 /* Disable (default state) */ +#define UART_OMAP_TXFIFO_LVL 0x1A /* TX FIFO fullness */ /* * These are definitions for the Exar XR17V35X and XR17(C|D)15X -- 2.7.4