Hi Peter,
On 2016-02-03 00:16, Peter Hurley wrote:
Won't this turn on h/w flow control for designs where RTS/CTS
is unconnected?
I don't believe so. What I believe it will do is flag the physical
device as being capable of supporting H/W flow control, which all
devices supported by omap-serial.c are. It will not enable h/w flow
control, as you may or may not want it for your particular setup. You
may have a UART that supports h/w flow control, but not physical wire
connection for RTS signal.
My understanding of the code is that this code
if (termios->c_cflag & CRTSCTS && up->port.flags & UPF_HARD_FLOW) {
/* Enable AUTORTS and AUTOCTS */
up->efr |= UART_EFR_CTS | UART_EFR_RTS;
in serial_omap_set_termios() will mean that h/w flow control will not
be enabled unless requested via termios.
In fact, without the UPF_HARD_FLOW flag set in the up->port.flags, it
is not possible to enable h/w flow-control, and any request to do so via
termios will silently fail.
Without this UPF_BOOT_AUTOCONF flag set, the serial_omap_config_port()
configuration function is never called for the omap-serial device. This
function is written and has the code to enable UPF_SOFT_FLOW and
UPF_HARD_FLOW, as well as to flag the port as type = PORT_OMAP. However
it is (I presume accidentally) dead code without the UPF_BOOT_AUTOCONF
flag. This is because the call to the serial_omap_config_port() function
is protected in serial_core.c by a test for the flag UPF_BOOT_AUTOCONF .
if (port->flags & UPF_BOOT_AUTOCONF) {
if (!(port->flags & UPF_FIXED_TYPE)) {
port->type = PORT_UNKNOWN;
flags |= UART_CONFIG_TYPE;
}
port->ops->config_port(port, flags); // this is a pointer to
the device specific configuration function, serial_omap_config_port in
this case
}
You can compare this to the behaviour of the 8250/8250_core.c driver,
which I think (but am unsure) that the omap-serial driver was based on.
It's serial8250_register_8250_port function (called by
serial8250_probe()), specifically sets the UPF_BOOT_AUTOCONF flag. As do
many of the other serial drivers.
uart->port.flags = up->port.flags | UPF_BOOT_AUTOCONF;
Without this patch, we are not able to turn on h/w flow control.
Thanks,
Greg
On 2016-02-03 00:16, Peter Hurley wrote:
On 01/25/2016 04:00 AM, Greg Farrell wrote:
Enable the UPF_BOOT_AUTOCONF flag in serial_omap_probe().
This will cause serial_omap_config_port() to be run and
the hardware to correctly be flagged as supporting hardware
and software flow-control.
Without this, it is not possible to enable flow control.
Won't this turn on h/w flow control for designs where RTS/CTS
is unconnected?
Signed-off-by: Greg Farrell <greg@xxxxxxxxxxxxxxx>
---
drivers/tty/serial/omap-serial.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/drivers/tty/serial/omap-serial.c
b/drivers/tty/serial/omap-serial.c
index b645f92..5e82238 100644
--- a/drivers/tty/serial/omap-serial.c
+++ b/drivers/tty/serial/omap-serial.c
@@ -1664,7 +1664,10 @@ static int serial_omap_probe(struct
platform_device *pdev)
sprintf(up->name, "OMAP UART%d", up->port.line);
up->port.mapbase = mem->start;
up->port.membase = base;
- up->port.flags = omap_up_info->flags;
+ /*
+ * Enable UPF_BOOT_AUTOCONF so that serial_omap_config_port will
execute
+ */
+ up->port.flags = omap_up_info->flags | UPF_BOOT_AUTOCONF;
up->port.uartclk = omap_up_info->uartclk;
up->port.rs485_config = serial_omap_config_rs485;
if (!up->port.uartclk) {
--
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