>-----Original Message-----
>From: Karicheri, Muralidharan
>Sent: Friday, May 09, 2014 11:30 AM
>To: Karicheri, Muralidharan; devicetree@xxxxxxxxxxxxxxx; linux-doc@xxxxxxxxxxxxxxx;
>linux-kernel@xxxxxxxxxxxxxxx; linux-serial@xxxxxxxxxxxxxxx
>Cc: Rob Herring; Pawel Moll; Mark Rutland; Ian Campbell; Kumar Gala; Randy Dunlap;
>Greg Kroah-Hartman; Jiri Slaby; Shilimkar, Santosh
>Subject: RE: [PATCH v2] serial: uart: add hw flow control support configuration
>
>>-----Original Message-----
>>From: Karicheri, Muralidharan
>>Sent: Thursday, May 01, 2014 3:05 PM
>>To: devicetree@xxxxxxxxxxxxxxx; linux-doc@xxxxxxxxxxxxxxx;
>>linux-kernel@xxxxxxxxxxxxxxx; linux-serial@xxxxxxxxxxxxxxx
>>Cc: Karicheri, Muralidharan; Rob Herring; Pawel Moll; Mark Rutland; Ian
>>Campbell; Kumar Gala; Randy Dunlap; Greg Kroah-Hartman; Jiri Slaby;
>>Shilimkar, Santosh
>>Subject: [PATCH v2] 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.
>>
>>Signed-off-by: Murali Karicheri <m-karicheri2@xxxxxx>
>>
>>CC: Rob Herring <robh+dt@xxxxxxxxxx>
>>CC: Pawel Moll <pawel.moll@xxxxxxx>
>>CC: Mark Rutland <mark.rutland@xxxxxxx>
>>CC: Ian Campbell <ijc+devicetree@xxxxxxxxxxxxxx>
>>CC: Kumar Gala <galak@xxxxxxxxxxxxxx>
>>CC: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
>>CC: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
>>CC: Jiri Slaby <jslaby@xxxxxxx>
>>CC: Santosh Shilimkar <santosh.shilimkar@xxxxxx>
>>---
>> .../devicetree/bindings/serial/of-serial.txt | 1 +
>> 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, 18 insertions(+), 5 deletions(-)
>>
>>diff --git a/Documentation/devicetree/bindings/serial/of-serial.txt
>>b/Documentation/devicetree/bindings/serial/of-serial.txt
>>index 1928a3e..7705477 100644
>>--- a/Documentation/devicetree/bindings/serial/of-serial.txt
>>+++ b/Documentation/devicetree/bindings/serial/of-serial.txt
>>@@ -37,6 +37,7 @@ 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.
>>+- has-hw-flow-control: the hardware has flow control capability.
>>
>> Example:
>>
>>diff --git a/drivers/tty/serial/8250/8250_core.c
>>b/drivers/tty/serial/8250/8250_core.c
>>index 0e1bf88..b69aff2 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..77ec6a1 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,
>>+ "has-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 b68550d..851707a 100644
>>--- a/drivers/tty/serial/serial_core.c
>>+++ b/drivers/tty/serial/serial_core.c
>>@@ -174,8 +174,12 @@ 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;
>>@@ -2772,7 +2776,9 @@ 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
>
>Any idea who is going to pick this patch for merge?
>
>Murali
Greg,
Could you please merge this patch to the tree? I assume you are the maintainer for serial driver. If not, please forward this to the right person.
Thanks and regards,
Murali
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