Hi Kaneko-san, Mizuguchi-san,
On Sun, Jun 14, 2015 at 7:26 PM, Yoshihiro Kaneko <ykaneko0929@xxxxxxxxx> wrote:
> From: Kazuya Mizuguchi <kazuya.mizuguchi.ks@xxxxxxxxxxx>
>
> 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@xxxxxxxxxxx>
> Signed-off-by: Yoshihiro Kaneko <ykaneko0929@xxxxxxxxx>
> ---
>
> 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@xxxxxxxxxxxxxx
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
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