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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 <finik@ti.com>
Signed-off-by: Alexander Savchenko <oleksandr.savchenko@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
hifive-unleashed-5.1
Dmitry Fink 2013-07-08 13:04:44 +03:00 committed by Greg Kroah-Hartman
parent f64ffda60e
commit c441508421
2 changed files with 3 additions and 1 deletions
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3
drivers/tty/serial/omap-serial.c
View File

@ -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);

1
include/uapi/linux/serial_reg.h
View File

@ -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