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serial: bfin_sport_uart: only enable SPORT TX if data is to be sent

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Rather than always turn on the SPORT TX interrupt, only do it when we've
actually queued up data for transmission.  This avoids useless interrupt
processing.

Signed-off-by: Sonic Zhang <sonic.zhang@analog.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Sonic Zhang 2010-03-09 12:25:37 -05:00 committed by Greg Kroah-Hartman
parent 60bd940f14
commit 9356c46170
1 changed files with 21 additions and 9 deletions
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30
drivers/serial/bfin_sport_uart.c
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@ -54,7 +54,7 @@ struct sport_uart_port {
#endif
};
static void sport_uart_tx_chars(struct sport_uart_port *up);
static int sport_uart_tx_chars(struct sport_uart_port *up);
static void sport_stop_tx(struct uart_port *port);
static inline void tx_one_byte(struct sport_uart_port *up, unsigned int value)
@ -307,18 +307,24 @@ static int sport_startup(struct uart_port *port)
return ret;
}
static void sport_uart_tx_chars(struct sport_uart_port *up)
/*
* sport_uart_tx_chars
*
* ret 1 means need to enable sport.
* ret 0 means do nothing.
*/
static int sport_uart_tx_chars(struct sport_uart_port *up)
{
struct circ_buf *xmit = &up->port.state->xmit;
if (SPORT_GET_STAT(up) & TXF)
return;
return 0;
if (up->port.x_char) {
tx_one_byte(up, up->port.x_char);
up->port.icount.tx++;
up->port.x_char = 0;
return;
return 1;
}
if (uart_circ_empty(xmit) || uart_tx_stopped(&up->port)) {
@ -329,7 +335,7 @@ static void sport_uart_tx_chars(struct sport_uart_port *up)
*/
if (SPORT_GET_STAT(up) & TXHRE)
sport_stop_tx(&up->port);
return;
return 0;
}
while(!(SPORT_GET_STAT(up) & TXF) && !uart_circ_empty(xmit)) {
@ -340,6 +346,8 @@ static void sport_uart_tx_chars(struct sport_uart_port *up)
if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
uart_write_wakeup(&up->port);
return 1;
}
static unsigned int sport_tx_empty(struct uart_port *port)
@ -361,6 +369,9 @@ static void sport_stop_tx(struct uart_port *port)
pr_debug("%s enter\n", __func__);
if (!(SPORT_GET_TCR1(up) & TSPEN))
return;
/* Although the hold register is empty, last byte is still in shift
* register and not sent out yet. So, put a dummy data into TX FIFO.
* Then, sport tx stops when last byte is shift out and the dummy
@ -383,11 +394,12 @@ static void sport_start_tx(struct uart_port *port)
pr_debug("%s enter\n", __func__);
/* Write data into SPORT FIFO before enable SPROT to transmit */
sport_uart_tx_chars(up);
if (sport_uart_tx_chars(up)) {
/* Enable transmit, then an interrupt will generated */
SPORT_PUT_TCR1(up, (SPORT_GET_TCR1(up) | TSPEN));
SSYNC();
}
/* Enable transmit, then an interrupt will generated */
SPORT_PUT_TCR1(up, (SPORT_GET_TCR1(up) | TSPEN));
SSYNC();
pr_debug("%s exit\n", __func__);
}