>-----Original Message----- >From: Karicheri, Muralidharan >Sent: Friday, April 11, 2014 3:18 PM >To: [email protected]; [email protected]; >[email protected]; >[email protected] >Cc: Balbi, Felipe; Karicheri, Muralidharan; Rob Herring; Mark Rutland; Ian >Campbell; >Kumar Gala; Randy Dunlap; Greg Kroah-Hartman; Jiri Slaby >Subject: [PATCH] serial: uart: add hw flow control support configuration > >8250 uart driver currently supports only software assisted hw flow control. >The software >assisted hw flow control maintains a hw_stopped flag in the tty structure to >stop and start >transmission and use modem status interrupt for the event to drive the >handshake signals. >This is not needed if hw has flow control capabilities. This patch adds a DT >attribute for >enabling hw flow control for a uart port. Also skip stop and start if this >flag is present in flag >field of the port structure. > >CC: Rob Herring <[email protected]> >CC: Pawel Moll <[email protected]> >CC: Mark Rutland <[email protected]> >CC: Ian Campbell <[email protected]> >CC: Kumar Gala <[email protected]> >CC: Randy Dunlap <[email protected]> >CC: Greg Kroah-Hartman <[email protected]> >CC: Jiri Slaby <[email protected]> > >Signed-off-by: Murali Karicheri <[email protected]> >--- > .../devicetree/bindings/serial/of-serial.txt | 2 ++ > drivers/tty/serial/8250/8250_core.c | 6 ++++-- > drivers/tty/serial/of_serial.c | 4 ++++ > drivers/tty/serial/serial_core.c | 12 +++++++++--- > 4 files changed, 19 insertions(+), 5 deletions(-) > >diff --git a/Documentation/devicetree/bindings/serial/of-serial.txt >b/Documentation/devicetree/bindings/serial/of-serial.txt >index 1928a3e..123de01 100644 >--- a/Documentation/devicetree/bindings/serial/of-serial.txt >+++ b/Documentation/devicetree/bindings/serial/of-serial.txt >@@ -37,6 +37,8 @@ Optional properties: > - auto-flow-control: one way to enable automatic flow control support. The > driver is allowed to detect support for the capability even without this > property. >+- hw-flow-control: this enables pure hw flow control and no software >+ intervention needed. > > Example: > >diff --git a/drivers/tty/serial/8250/8250_core.c >b/drivers/tty/serial/8250/8250_core.c >index 81f909c..6b1b868 100644 >--- a/drivers/tty/serial/8250/8250_core.c >+++ b/drivers/tty/serial/8250/8250_core.c >@@ -2338,9 +2338,11 @@ serial8250_do_set_termios(struct uart_port *port, struct >ktermios *termios, > * the trigger, or the MCR RTS bit is cleared. In the case where > * the remote UART is not using CTS auto flow control, we must > * have sufficient FIFO entries for the latency of the remote >- * UART to respond. IOW, at least 32 bytes of FIFO. >+ * UART to respond. IOW, at least 32 bytes of FIFO. Also enable >+ * AFE if hw flow control is supported > */ >- if (up->capabilities & UART_CAP_AFE && port->fifosize >= 32) { >+ if ((up->capabilities & UART_CAP_AFE && (port->fifosize >= 32)) || >+ port->flags & UPF_HARD_FLOW) { > up->mcr &= ~UART_MCR_AFE; > if (termios->c_cflag & CRTSCTS) > up->mcr |= UART_MCR_AFE; >diff --git a/drivers/tty/serial/of_serial.c b/drivers/tty/serial/of_serial.c >index >9924660..1a5f528 100644 >--- a/drivers/tty/serial/of_serial.c >+++ b/drivers/tty/serial/of_serial.c >@@ -182,6 +182,10 @@ static int of_platform_serial_probe(struct >platform_device *ofdev) > "auto-flow-control")) > port8250.capabilities |= UART_CAP_AFE; > >+ if (of_property_read_bool(ofdev->dev.of_node, >+ "hw-flow-control")) >+ port8250.port.flags |= UPF_HARD_FLOW; >+ > ret = serial8250_register_8250_port(&port8250); > break; > } >diff --git a/drivers/tty/serial/serial_core.c >b/drivers/tty/serial/serial_core.c >index 2cf5649..16e3615 100644 >--- a/drivers/tty/serial/serial_core.c >+++ b/drivers/tty/serial/serial_core.c >@@ -170,8 +170,12 @@ static int uart_port_startup(struct tty_struct *tty, >struct >uart_state *state, > if (tty->termios.c_cflag & CBAUD) > uart_set_mctrl(uport, TIOCM_RTS | TIOCM_DTR); > } >- >- if (tty_port_cts_enabled(port)) { >+ /* >+ * if hw support flow control without software intervention, >+ * then skip the below check >+ */ >+ if (tty_port_cts_enabled(port) && >+ !(uport->flags & UPF_HARD_FLOW)) { > spin_lock_irq(&uport->lock); > if (!(uport->ops->get_mctrl(uport) & TIOCM_CTS)) > tty->hw_stopped = 1; >@@ -2768,7 +2772,9 @@ void uart_handle_cts_change(struct uart_port *uport, >unsigned >int status) > > uport->icount.cts++; > >- if (tty_port_cts_enabled(port)) { >+ /* skip below code if the hw flow control is supported */ >+ if (tty_port_cts_enabled(port) && >+ !(uport->flags & UPF_HARD_FLOW)) { > if (tty->hw_stopped) { > if (status) { > tty->hw_stopped = 0; >-- >1.7.9.5
Can this be queued up for merge if looks good? Murali Karicheri Linux Kernel, Software Development -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
