Re: [PATCH v2] serial: OMAP: add RS485 support

[Greg KH <gregkh@linuxfoundation.org>]

On Tue, Aug 13, 2013 at 12:54:47PM +0200, Javier Martinez Canillas wrote:
> On Tue, Aug 13, 2013 at 12:22 PM, Mark Jackson <mpfj-list@newflow.co.uk> wrote:
> > On 12/08/13 23:56, Greg KH wrote:
> >> On Sun, Aug 11, 2013 at 02:56:50PM +0100, Mark Jackson wrote:
> >>> This patch adds RS485 support to the OMAP serial driver, as
> >>> defined in:-
> >>>
> >>> Documentation/devicetree/bindings/serial/rs485.txt
> >>>
> >>> When a UART transmitter is connected to (eg) a RS485 driver, it is
> >>> necessary to turn the driver on/off as quickly as possible.  This is
> >>> best achieved in the serial driver itself (rather than in userspace
> >>> where the latency can be quite large).
> >>>
> >>> This patch allows a GPIO pin to be defined (via DT) that controls
> >>> the enabling of the driver at the start of a message, and disables
> >>> the driver when the message has been completed.
> >>>
> >>> When RS485 is disabled, the RTS pin is set to on.
> >>>
> >>> Signed-off-by: Mark Jackson <mpfj@newflow.co.uk>
> >>> ---
> >>> Changes in v2:
> >>> - Fix incorrect logic in serial_omap_config_rs485()
> >>>
> >>>  drivers/tty/serial/omap-serial.c |  178 ++++++++++++++++++++++++++++++++++++++
> >>>  1 file changed, 178 insertions(+)
> >>
> >> This doesn't apply to my tty-next branch:
> >>       checking file drivers/tty/serial/omap-serial.c
> >>       Hunk #1 FAILED at 40.
> >>       Hunk #2 succeeded at 162 (offset 6 lines).
> >>       Hunk #3 succeeded at 280 (offset 5 lines).
> >>       Hunk #4 succeeded at 378 (offset 6 lines).
> >>       Hunk #5 succeeded at 1312 (offset 8 lines).
> >>       Hunk #6 succeeded at 1405 (offset 8 lines).
> >>       Hunk #7 succeeded at 1528 (offset 10 lines).
> >>       Hunk #8 FAILED at 1638.
> >>       Hunk #9 succeeded at 1705 (offset 6 lines).
> >>       2 out of 9 hunks FAILED
> >>
> >> so I can't apply it, sorry.
> >
> > It was applied on top of Linus' tree, if that makes any difference.
> >
> > I'll rebase onto yours and re-post the patch.
> > --
> 
> Hi Mark,
> 
> I've seen several attempts to add RS485 support to the omap serial
> driver and it is always nack-ed. There seems to be concerns about
> controlling the RTS by software when RS485 is not supported by the
> UART hardware. Please refer to [1] and [2] for more information.

Hm, but we do support RS485 now in the kernel, look at
Documentation/serial/serial-rs485.txt.  Why can't this driver support it
as well if the serial core already does?

thanks,

greg k-h