[PATCH 10/13] serial: bfin_sport_uart: only enable SPORT TX if data is to be sent
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From: Mike Frysinger on 9 Mar 2010 12:30 From: Sonic Zhang <sonic.zhang(a)analog.com> 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(a)analog.com> Signed-off-by: Mike Frysinger <vapier(a)gentoo.org> --- drivers/serial/bfin_sport_uart.c | 30 +++++++++++++++++++++--------- 1 files changed, 21 insertions(+), 9 deletions(-) diff --git a/drivers/serial/bfin_sport_uart.c b/drivers/serial/bfin_sport_uart.c index 1b22c59..9d777e4 100644 --- a/drivers/serial/bfin_sport_uart.c +++ b/drivers/serial/bfin_sport_uart.c @@ -53,7 +53,7 @@ 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) @@ -306,18 +306,24 @@ 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)) { @@ -328,7 +334,7 @@ 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)) { @@ -339,6 +345,8 @@ 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) @@ -360,6 +368,9 @@ 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 @@ -382,11 +393,12 @@ 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__); } -- 1.7.0.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |