Hi Christoph,
On Mon, Aug 15, 2016 at 1:20 PM, Baumann, Christoph (C.)
<cbaumann@xxxxxxxxxxx> wrote:
> working on getting RTS/CTS run on r8a7795 I had some annoying issues.
Which port are you using? SCIF or HSCIF?
> Measuring with a scope showed that RTS would become low on opening the tty device (regardless of having CRTSCTS set or not). So far this is expected.
> But if I used tcsetattr() to set/unset the CRTSCTS flag the RTS pin would become hi and stayed so.
> I then looked into the sh-sci driver and added some debug output.
> My analysis was that upon opening the tty device the functions set_termios and set_mctrl are called.
> In the sh-sci driver the set_mctrl function is the only place where the internal 'autorts' flag is actually written to a register.
> As obviously the RTSCTS flow control flag can only be set after the device is opened, the flag isn't propagated to the corresponding register.
You mean sci_set_mctrl() isn't called by the serial core after
sci_set_termios()?
However, uart_set_termios() calls both uart_change_speed() and
uart_{clear,set}_mctrl(), in that order?
> To make it more confusing the flag is kept in .c_cflag even after closing the device and is then taken care of the next time the device is opened again.
> To fix this I set the bit in set_termios after the line where it was previously only stored in the bool variable 'autorts' (see attachment).
> --- a/drivers/tty/serial/sh-sci.c
> +++ b/drivers/tty/serial/sh-sci.c
[ removed unrelated changes]
> @@ -2336,6 +2337,8 @@ done:
> port->status |= UPSTAT_AUTOCTS;
> /* MCE is enabled when RTS is raised */
> s->autorts = true;
> + ctrl |= SCFCR_MCE;
> + sci_set_rts(port, 1);
> }
>
> /*
Have you tried using GPIO RTS/CTS instead of hardware-assisted RTS/CTS?
Does it show the same behavior?
When adding support for hardware-assisted RTS/CTS, I used the behavior of
GPIO RTS/CTS as the expected behavior.
Thanks!
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
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