From mboxrd@z Thu Jan 1 00:00:00 1970 From: Yoshihiro Kaneko Date: Sun, 14 Jun 2015 17:26:26 +0000 Subject: [PATCH/RFC] serial: sh-sci: Fix issue of frequent rx_full interrupt Message-Id: <1434302786-31162-1-git-send-email-ykaneko0929@gmail.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-serial@vger.kernel.org Cc: Greg Kroah-Hartman , Simon Horman , Magnus Damm , linux-sh@vger.kernel.org From: Kazuya Mizuguchi When the receive FIFO is not read in PIO transfer, rx_full interrupt occurs frequently. This patch avoids it by discarding the receive FIFO. Signed-off-by: Kazuya Mizuguchi Signed-off-by: Yoshihiro Kaneko --- This patch is based on the tty-next branch of Greg Kroah-Hartman's tty tree. drivers/tty/serial/sh-sci.c | 22 ++++++++++++++++++++-- 1 file changed, 20 insertions(+), 2 deletions(-) diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c index b74a644..4ec3c32 100644 --- a/drivers/tty/serial/sh-sci.c +++ b/drivers/tty/serial/sh-sci.c @@ -121,6 +121,8 @@ struct sci_port { #endif struct notifier_block freq_transition; + + u64 rxfull_time; }; /* Function prototypes */ @@ -690,12 +692,26 @@ static void sci_receive_chars(struct uart_port *port) return; while (1) { + int rxfill = sci_rxfill(port); + u64 now = get_jiffies_64(); /* Don't copy more bytes than there is room for in the buffer */ - count = tty_buffer_request_room(tport, sci_rxfill(port)); + count = tty_buffer_request_room(tport, rxfill); /* If for any reason we can't copy more data, we're done! */ - if (count = 0) + if (count = 0) { + int n; + /* discarded bytes in RX-FIFO */ + for (n = 0; n < rxfill; n++) + serial_port_in(port, SCxRDR); + if (rxfill > 0 && + time_after64(now, sci_port->rxfull_time + (5*HZ))) { + sci_port->rxfull_time = now; + dev_warn(port->dev, + "RX-FIFO isn't read, so %d bytes is discarded.\n", + rxfill); + } break; + } if (port->type = PORT_SCI) { char c = serial_port_in(port, SCxRDR); @@ -2342,6 +2358,8 @@ static int sci_init_single(struct platform_device *dev, dev_dbg(port->dev, "DMA tx %d, rx %d\n", p->dma_slave_tx, p->dma_slave_rx); + sci_port->rxfull_time = get_jiffies_64(); + return 0; } -- 1.9.1