Hi Peter,
On Fri, Apr 29, 2016 at 5:59 PM, Peter Hurley <pe...@hurleysoftware.com> wrote:
> On 04/29/2016 05:58 AM, Geert Uytterhoeven wrote:
>> Correct pin initialization on (H)SCIF:
>> - RTS must be deasserted (it's active low),
>> - SCK must be an input, as it may be used as the optional external
>> clock input.
>>
>> Initial pin configuration must always be done:
>> - Regardless of the presence of dedicated RTS and CTS pins: if the
>> register exists, the RTS/CTS bits exist, too,
>> - Regardless of hardware flow control being enabled or not: RTS must
>> be deasserted.
>
> This is always setting RTS active; why?
No, it deasserts RTS. RTS is active-low, so setting the pin state to 1/high
(setting the SCSPTR_RTSDT bit), makes RTS inactive.
Before, the code didn't set the SCSPTR_RTSDT bit, so the pin might have
been low, i.e. RTS may have been active.
> Normally you want to program RTS only in response to ->set_mctrl()
> from serial core. For example, this will set RTS active even though
> baud might be set to B0.
Yes, that's also my understanding.
>> Signed-off-by: Geert Uytterhoeven <geert+rene...@glider.be>
>> ---
>> v2:
>> - New.
>> ---
>> drivers/tty/serial/sh-sci.c | 23 ++++++++---------------
>> 1 file changed, 8 insertions(+), 15 deletions(-)
>>
>> diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c
>> index ce7bd165929ea078..c46999f20917964e 100644
>> --- a/drivers/tty/serial/sh-sci.c
>> +++ b/drivers/tty/serial/sh-sci.c
>> @@ -712,21 +712,14 @@ static void sci_init_pins(struct uart_port *port,
>> unsigned int cflag)
>> return;
>> }
>>
>> - /*
>> - * For the generic path SCSPTR is necessary. Bail out if that's
>> - * unavailable, too.
>> - */
>> - if (!sci_getreg(port, SCSPTR)->size)
>> - return;
>> -
>> - if ((s->cfg->capabilities & SCIx_HAVE_RTSCTS) &&
>> - ((!(cflag & CRTSCTS)))) {
>> - unsigned short status;
>> -
>> - status = serial_port_in(port, SCSPTR);
>> - status &= ~SCSPTR_CTSIO;
>> - status |= SCSPTR_RTSIO;
>> - serial_port_out(port, SCSPTR, status); /* Set RTS = 1 */
>> + if (sci_getreg(port, SCSPTR)->size) {
>> + u16 status = serial_port_in(port, SCSPTR);
>> +
>> + /* RTS# is output, driven 1 */
>> + status |= SCSPTR_RTSIO | SCSPTR_RTSDT;
>> + /* CTS# and SCK are inputs */
>> + status &= ~(SCSPTR_CTSIO | SCSPTR_SCKIO);
>> + serial_port_out(port, SCSPTR, status);
>> }
>> }
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- ge...@linux-m68k.org
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
