| Message ID | 1434302786-31162-1-git-send-email-ykaneko0929@gmail.com (mailing list archive) |
|---|---|
| State | RFC |
| Delegated to: | Simon Horman |
| Headers | show |
Hi Kaneko-san, Mizuguchi-san, On Sun, Jun 14, 2015 at 7:26 PM, Yoshihiro Kaneko <ykaneko0929@gmail.com> wrote: > From: Kazuya Mizuguchi <kazuya.mizuguchi.ks@renesas.com> > > 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 <kazuya.mizuguchi.ks@renesas.com> > Signed-off-by: Yoshihiro Kaneko <ykaneko0929@gmail.com> > --- > > 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); If I'm not mistaken, this means we loose data, without the tty user noticing? As data is discarded from the FIFO, we won't get an overrun condition later, and TTY_OVERRUN will never be inserted into the flip buffer. > + } > 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; > } Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds -- To unsubscribe from this list: send the line "unsubscribe linux-sh" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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; }