diff options
Diffstat (limited to 'drivers/tty/serial/sh-sci.c')
| -rw-r--r-- | drivers/tty/serial/sh-sci.c | 40 |
1 files changed, 31 insertions, 9 deletions
diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c index 5bf997253a46..e7d6566fafaf 100644 --- a/drivers/tty/serial/sh-sci.c +++ b/drivers/tty/serial/sh-sci.c @@ -1991,18 +1991,40 @@ static void sci_set_termios(struct uart_port *port, struct ktermios *termios, #ifdef CONFIG_SERIAL_SH_SCI_DMA /* - * Calculate delay for 1.5 DMA buffers: see - * drivers/serial/serial_core.c::uart_update_timeout(). With 10 bits - * (CS8), 250Hz, 115200 baud and 64 bytes FIFO, the above function + * Calculate delay for 2 DMA buffers (4 FIFO). + * See drivers/serial/serial_core.c::uart_update_timeout(). With 10 + * bits (CS8), 250Hz, 115200 baud and 64 bytes FIFO, the above function * calculates 1 jiffie for the data plus 5 jiffies for the "slop(e)." - * Then below we calculate 3 jiffies (12ms) for 1.5 DMA buffers (3 FIFO - * sizes), but it has been found out experimentally, that this is not - * enough: the driver too often needlessly runs on a DMA timeout. 20ms - * as a minimum seem to work perfectly. + * Then below we calculate 5 jiffies (20ms) for 2 DMA buffers (4 FIFO + * sizes), but when performing a faster transfer, value obtained by + * this formula is may not enough. Therefore, if value is smaller than + * 20msec, this sets 20msec as timeout of DMA. */ if (s->chan_rx) { - s->rx_timeout = (port->timeout - HZ / 50) * s->buf_len_rx * 3 / - port->fifosize / 2; + unsigned int bits; + + /* byte size and parity */ + switch (termios->c_cflag & CSIZE) { + case CS5: + bits = 7; + break; + case CS6: + bits = 8; + break; + case CS7: + bits = 9; + break; + default: + bits = 10; + break; + } + + if (termios->c_cflag & CSTOPB) + bits++; + if (termios->c_cflag & PARENB) + bits++; + s->rx_timeout = DIV_ROUND_UP((s->buf_len_rx * 2 * bits * HZ) / + (baud / 10), 10); dev_dbg(port->dev, "DMA Rx t-out %ums, tty t-out %u jiffies\n", s->rx_timeout * 1000 / HZ, port->timeout); if (s->rx_timeout < msecs_to_jiffies(20)) |