Le 09/12/2014 14:31, Cyrille Pitchen a écrit : > This patch fixes many bugs in the code dealing with the hardware handshake. > > As an example, in atmel_set_termios(), we used to test whether the CRTSCTS > c_cflag was set. If so, we selected the "Hardware Handshake" mode through the > Mode Register. However, few lines below the mode was reset to "Normal" (0). > So there was no way to select the "Hardware Handshake" mode. To fix this > issue, > we moved the CRTSCRTS c_cflag test AFTER the mode has been reset to "Normal". > > Also setting the RTSEN and RTSDIS bits in the Control Register has different > results whether the USART is set in "Normal" or "Hardware Handshake" mode: > > 1) "Normal" mode > - the RTSEN bit forces the RTS line to low level, which tells the remote peer > that we are ready to received new data. > - the RTSDIS bit forces the RTS line to high level, which tells the remote > peer > to stop sending new data. > > 2) "Hardware Handshake" mode > - the RTSEN bit forces the RTS line to high level. > - the RTSDIS bit lets the hardware control the RTS line. > > WARNING: > when FIFOs are not available or not enabled, the RTS line is controlled by the > PDC. This is why using the Hardware Handshake mode requires using the PDC > channel for reception. However the Hardware Handshake mode DOES NOT work with > DMA controller since it cannot control the RTS line. > Future designs with FIFOs will introduce a new feature: the RTS line will be > controlled by the RX FIFO using thresholds. This patch was tested with this > new > design. > > Signed-off-by: Cyrille Pitchen <[email protected]>
Indeed. It fixes a pretty important misbehavior. Acked-by: Nicolas Ferre <[email protected]> Thanks. > --- > drivers/tty/serial/atmel_serial.c | 91 > ++++++++++++++++++++++++++------------- > 1 file changed, 61 insertions(+), 30 deletions(-) > > diff --git a/drivers/tty/serial/atmel_serial.c > b/drivers/tty/serial/atmel_serial.c > index 92a8b26..9e0c636 100644 > --- a/drivers/tty/serial/atmel_serial.c > +++ b/drivers/tty/serial/atmel_serial.c > @@ -341,13 +341,37 @@ static u_int atmel_tx_empty(struct uart_port *port) > static void atmel_set_mctrl(struct uart_port *port, u_int mctrl) > { > unsigned int control = 0; > - unsigned int mode; > + unsigned int mode = UART_GET_MR(port); > + unsigned int rts_paused, rts_ready; > struct atmel_uart_port *atmel_port = to_atmel_uart_port(port); > > + /* override mode to RS485 if needed, otherwise keep the current mode */ > + if (port->rs485.flags & SER_RS485_ENABLED) { > + if ((port->rs485.delay_rts_after_send) > 0) > + UART_PUT_TTGR(port, port->rs485.delay_rts_after_send); > + mode &= ~ATMEL_US_USMODE; > + mode |= ATMEL_US_USMODE_RS485; > + } > + > + /* set the RTS line state according to the mode */ > + if ((mode & ATMEL_US_USMODE) == ATMEL_US_USMODE_HWHS) { > + /* force RTS line to high level */ > + rts_paused = ATMEL_US_RTSEN; > + > + /* give the control of the RTS line back to the hardware */ > + rts_ready = ATMEL_US_RTSDIS; > + } else { > + /* force RTS line to high level */ > + rts_paused = ATMEL_US_RTSDIS; > + > + /* force RTS line to low level */ > + rts_ready = ATMEL_US_RTSEN; > + } > + > if (mctrl & TIOCM_RTS) > - control |= ATMEL_US_RTSEN; > + control |= rts_ready; > else > - control |= ATMEL_US_RTSDIS; > + control |= rts_paused; > > if (mctrl & TIOCM_DTR) > control |= ATMEL_US_DTREN; > @@ -359,23 +383,12 @@ static void atmel_set_mctrl(struct uart_port *port, > u_int mctrl) > mctrl_gpio_set(atmel_port->gpios, mctrl); > > /* Local loopback mode? */ > - mode = UART_GET_MR(port) & ~ATMEL_US_CHMODE; > + mode &= ~ATMEL_US_CHMODE; > if (mctrl & TIOCM_LOOP) > mode |= ATMEL_US_CHMODE_LOC_LOOP; > else > mode |= ATMEL_US_CHMODE_NORMAL; > > - /* Resetting serial mode to RS232 (0x0) */ > - mode &= ~ATMEL_US_USMODE; > - > - if (port->rs485.flags & SER_RS485_ENABLED) { > - dev_dbg(port->dev, "Setting UART to RS485\n"); > - if ((port->rs485.delay_rts_after_send) > 0) > - UART_PUT_TTGR(port, port->rs485.delay_rts_after_send); > - mode |= ATMEL_US_USMODE_RS485; > - } else { > - dev_dbg(port->dev, "Setting UART to RS232\n"); > - } > UART_PUT_MR(port, mode); > } > > @@ -1921,12 +1934,14 @@ static void atmel_set_termios(struct uart_port *port, > struct ktermios *termios, > struct ktermios *old) > { > unsigned long flags; > - unsigned int mode, imr, quot, baud; > + unsigned int old_mode, mode, imr, quot, baud; > + > + /* save the current mode register */ > + mode = old_mode = UART_GET_MR(port); > > - /* Get current mode register */ > - mode = UART_GET_MR(port) & ~(ATMEL_US_USCLKS | ATMEL_US_CHRL > - | ATMEL_US_NBSTOP | ATMEL_US_PAR > - | ATMEL_US_USMODE); > + /* reset the mode, clock divisor, parity, stop bits and data size */ > + mode &= ~(ATMEL_US_USCLKS | ATMEL_US_CHRL | ATMEL_US_NBSTOP | > + ATMEL_US_PAR | ATMEL_US_USMODE); > > baud = uart_get_baud_rate(port, termios, old, 0, port->uartclk / 16); > quot = uart_get_divisor(port, baud); > @@ -1971,12 +1986,6 @@ static void atmel_set_termios(struct uart_port *port, > struct ktermios *termios, > } else > mode |= ATMEL_US_PAR_NONE; > > - /* hardware handshake (RTS/CTS) */ > - if (termios->c_cflag & CRTSCTS) > - mode |= ATMEL_US_USMODE_HWHS; > - else > - mode |= ATMEL_US_USMODE_NORMAL; > - > spin_lock_irqsave(&port->lock, flags); > > port->read_status_mask = ATMEL_US_OVRE; > @@ -2020,18 +2029,40 @@ static void atmel_set_termios(struct uart_port *port, > struct ktermios *termios, > /* disable receiver and transmitter */ > UART_PUT_CR(port, ATMEL_US_TXDIS | ATMEL_US_RXDIS); > > - /* Resetting serial mode to RS232 (0x0) */ > - mode &= ~ATMEL_US_USMODE; > - > + /* mode */ > if (port->rs485.flags & SER_RS485_ENABLED) { > if ((port->rs485.delay_rts_after_send) > 0) > UART_PUT_TTGR(port, port->rs485.delay_rts_after_send); > mode |= ATMEL_US_USMODE_RS485; > + } else if (termios->c_cflag & CRTSCTS) { > + /* RS232 with hardware handshake (RTS/CTS) */ > + mode |= ATMEL_US_USMODE_HWHS; > + } else { > + /* RS232 without hadware handshake */ > + mode |= ATMEL_US_USMODE_NORMAL; > } > > - /* set the parity, stop bits and data size */ > + /* set the mode, clock divisor, parity, stop bits and data size */ > UART_PUT_MR(port, mode); > > + /* > + * when switching the mode, set the RTS line state according to the > + * new mode, otherwise keep the former state > + */ > + if ((old_mode & ATMEL_US_USMODE) != (mode & ATMEL_US_USMODE)) { > + unsigned int rts_state; > + > + if ((mode & ATMEL_US_USMODE) == ATMEL_US_USMODE_HWHS) { > + /* let the hardware control the RTS line */ > + rts_state = ATMEL_US_RTSDIS; > + } else { > + /* force RTS line to low level */ > + rts_state = ATMEL_US_RTSEN; > + } > + > + UART_PUT_CR(port, rts_state); > + } > + > /* set the baud rate */ > UART_PUT_BRGR(port, quot); > UART_PUT_CR(port, ATMEL_US_RSTSTA | ATMEL_US_RSTRX); > -- Nicolas Ferre -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
